FASTENER ENGINEERING HANDBOOK 2021

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2021 Fastener Handbook

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editorial

A future with clever bolts “Imagine a future with clever bolts that communicate when tensioned?” This was a phrase spoken at a wind-power conference years ago, long before the digital wind farms of today, many of which are remotely connected and monitored to ensure optimal performance. It was before the popularity of “smart” tools and the industrialization of the internet-of-things (IoT).

One utility-scale wind turbine has thousands of different-sized bolts. Correct tensioning is critical as one loose bolt could trigger a domino effect, resulting in damage to the entire structure. The idea of bolts that could “communicate” was groundbreaking at the time — and a potential game-changer for several industries.

Think of the anchors securing concrete beams or the fasteners in the suspension or brake system of an automobile. The ability to check on the fasteners in an assembly could ensure the long-term structural security of the application.

The initial “clever bolt” concept included a simple mechanism inside each fastener that worked as an indicator of the actual load or tension at the time of installation.

Since that conference, several smart tools have hit the market, offering combinations of precise torque monitoring, digital calibrations, and tool traceability.

However, the concept of connected fasteners that truly “communicate” wirelessly has been slower to develop. A few companies are changing that.

For example, German-based Sensorise SmartScrew System offers new technology for the continuous monitoring of dynamically loaded screws and bolts, such as for wind turbines. The system includes Sensorise SmartScrews, which install like any other screw but offer built-in sensors that measure the temperature and static loads on the screws and bolts. It collects this data for processing and analytics, and to remotely verify proper operation.

Hilti, a global power-tool company, has launched Tracefast, which leverages the IoT. These smart fasteners have a laser-print data matrix code, which is similar to a QR code, making each one identifiable and traceable. By using the Hilti Connect app on a smartphone, users can simply scan the code to view a fastener’s details, including the proper methods for installation method or its installed date.

In many cases, there’s no way to look at an installed fastener and have access to its full history. Smart, connected components are providing historical insight and quality assurance, which can lead to greater productivity and safety. Certainly, it could be argued that not every assembly requires such diligence. But it’s nice to have options and, particularly, for critical assemblies.

In this year’s annual Fastener Engineering Handbook, we cover fastener basics and advancements in adhesives, welding, and tools. We enjoy learning about and sharing the latest innovations. Thank you for reading!

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Engineering

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Contents 12 • 2021

28 _RINGS

When are adhesives and tapes the ideal choice for an application?

What are the technical factors to consider before choosing retaining rings for an assembly?

How to choose the ideal threadlocker for an application?

10 _ASSEMBLY: Fasteners How do I know which threaded fastener is right for my application?

12 _ASSEMBLY: Methods What methods are available to bond dissimilar metals for use in critical applications?

What are the typical riveting faults and how can they be avoided?

36 _SCREWS: Duplex Screws What is the difference between Duplex Nails and Screws?

38 _SCREWS: Security Screws What are tamper-proof seal screws and when should you use them?

40 _SUPPLY CHAIN

When does an application warrant the use of a bolt instead of a screw?

How to ensure a successful fastener supply chain?

16 _COUPLINGS

42 _TRAINING: Courses

How to avoid coupling failures?

Why is fastener training important?

18 _LATCHES

44 _TRAINING: FAQs

What are the different types of latches available for secure enclosures?

What are some critical structural fastener facts you should know?

20 _MANUFACTURING

46 _TOOLS

How fasteners can affect product testing and manufacturing?

What are the best practices for tool and equipment preventive maintenance?

What type of plastic is ideal for highperformance fasteners?

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32 _RIVETS

14 _BOLTS

22 _MATERIALS

64 _AD INDEX

fastenerengineering.com

4 _ADHESIVES: Tapes

8 _ADHESIVES: Threadlocker

58 _PROFILES

•

50 _WASHERS How do flat and lock washers differ?

24 _NUTS

52 _WELDING: Joints

What are twin nuts and how do they function?

When do joints need to be pre-heated before welding?

26 _PINS

54 _WELDING: Materials

How to select the proper pin for an application?

What advances in welding address material variations?

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Reese Weber Senior Application Engineer 3M Industrial Adhesives and Tapes Division

ADhesives: tapes

A design engineer applying tape for an industrial application.

When are adhesives and tapes the ideal choice for an application?

Today’s design engineers have an abundance of attachment options to choose from — which is likely a blessing and a curse. Undoubtedly, identifying the ideal adhesive or bonding solution for an application can be a challenge. This is particularly true given the factors that typically affect a project, such as costs, reliability, labor, and efficiency.

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For certain applications, more than one option can help a designer better achieve his or her bonding objectives.

To this end, tapes and adhesives are rapidly gaining acceptance in several markets. Their ease-of-use, durability, and ability to bond and seal simultaneously offer end-users flexibility when creating their design.

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This could include a combination of mechanical fasteners and adhesives.

What’s imperative, however, is to first understand the design attributes of each attachment option before weighing the pros and cons. What works for one application might not work for another.

Liquid adhesives versus tapes Liquid adhesives are applied in liquid form and rely on chemical reactions to occur to gain strength over time. This is typically referred to as the cure time.

These types of adhesives are available in several chemistries, with varying advantages and disadvantages.

Tapes are a different type of adhesive. They’re already cured or in a solid state yet are still tacky (or sticky) enough to adhere to certain substrates.

Tapes can be single-sided (like a giftwrapping tape) or double-sided and are either removable or permanent.

There are two categories of adhesives that are most commonly used for industrial attachment: 1. Liquid-applied structural adhesives 2. Acrylic foam tapes Both bonding options are incredibly durable and proven to last the life of the bond. However, they differ significantly when it comes to process flexibility, surface preparation, stress-resistance capability, and a few other features.

It’s important to consider each one within a holistic view of the attachment process to identify the ideal method for an application.

For example, consider the: •

•

Substrates to be bonded – joining two pieces of aluminum will likely call for a different solution than bonding polypropylene to thermoplastic because of how readily adhesives adhere to these substrates.

Stresses acting on the bond – does the attachment have specific strength requirements or industry certifications it needs to pass?

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•

•

Design or geometry of the joint – consider how the substrates will join.

For example, is the bond area flat, curved, or multi-dimensional?

The environment – think about the conditions where the final assembly be placed (how hot, humid, cold, or wet, etc.?).

Liquid-applied structural adhesives Structural adhesives are one of the strongest adhesives available and their strength in bonding comes closest to that of welds. Once cured, structural adhesives have overlap shear strengths between 1,000 and 5,000 psi (6.9 and 34.5 MPa). This means they’re extremely resistant to changes in the environment.

Two of the most common types of structural adhesives are acrylics and epoxies, which have a number of distinct attributes.

•

Acrylics: o Cures and builds strength at a much faster rate than other structural adhesives o High tolerances for unprepared bonding surfaces o Available in low-odor options

•

Epoxies: o Highest bond strength and overall performance o Strongest durability in harsh environments o Typically require more surface preparation than acrylics

Under equal stress conditions, metal panels bonded with acrylic foam tape (left) show no visible sign of stress compared to those with mechanical fasteners (right).

The substrate Common mechanical attachments, such as welding or using screws or rivets, can potentially damage assembled substrates. Screws and rivets puncture through the substrate, while the extreme temperature levels of welding can cause thermal distortion to the surrounding material.

Adhesives inherently interact or react with only the surfaces of the substrates that they adhere to and bond. Keeping the original substrates intact offers several advantages, including: • •

• •

•

Leak reduction. The puncturing of substrates can lead to water ingress and damage, which should be avoided.

Smooth aesthetic. By ensuring no punctures or thermal distortions, the substrate maintains its original smoothness. In the case of low modulus liquid adhesives or adhesive tapes, shrinkage is also avoided.

Lightweighting. Thinner gauge materials can be used with adhesives, which reduces end-product costs and weight.

Uniform stress distribution. Adhesives distribute stresses across the entire bond line, which reduces stress concentration typical of screw or rivet points.

Attaching dissimilar materials. Adhesives prevent galvanic corrosion between dissimilar metals. Plus, flexible adhesives can move with differential thermal expansion and contraction.

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ADhesives: tapes Structural adhesives have far greater strength than acrylic foam tapes, but they have a set work life (the duration between the dispensing and the fixture of the second part).

Once fixtured, adhesives gain strength relatively quickly, typically reaching handling strength (>50 psi (345 kPa)) in under an hour, with a longer time needed to reach a full cure.

However, these time constraints and fixture requirements can create logistical challenges because the parts must be staged and sit idle before they achieve handling strength and a full cure.

Acrylic foam tapes Acrylic foam tapes (AFT) were invented in 1980 and are considered one of the newer bonding solutions. General foam tapes are typically made from laminating thin “skins” of adhesive onto the face sides of a commercially available foam.

AFTs offer an adhesive foam core (one that’s 100% adhesive throughout), which allows for bonding and sealing to take place simultaneously. This viscoelastic adhesive core also excels at dissipating stresses and absorbing energy, providing further unique bonding properties including the following: •

•

•

Dynamic loading strength. Offers greater dynamic loading strengths than general foam tapes, commonly demonstrating an ultimate tensile and shear strength of between 60 and 100 psi (410 and 690 kPa).

Noise and vibration reduction. The viscoelastic adhesive core absorbs and dissipates energy to reduce noise and vibration.

Part movement. AFT can withstand 300% shear strain, so it can move with large parts that are expanding and contracting at different rates

Acrylic foam tapes are also one of the easiest formulas to apply of all of the bonding solutions. The tape requires moderate levels of surface preparation.

This includes cleaning and, depending

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A structural adhesive is applied to a stiffener prior to panel attachment. Stiffeners are attached to thinner-gauge metal panels to add rigidity.

on the bonding surface, the application of a primer. But a fully cured state allows for immediate handling strength, with no clamping or fixturing necessary.

Once pressure has been applied to both sides of the tape, the bond is instantly at 30 to 40% of its final bond strength. This immediate strength lets end-users move an application anywhere, instantly, without the need for a staging area to allow it to cure.

AFTs provide the greatest process flexibility through ease of use, immediate handling strength, and aesthetically pleasing results. On the other hand, structural adhesives have more complicated and less efficient processes, but provide the greatest shear strength performance needed for an application.

In sum, the entire application process, including labor, cost, aesthetics, and load performance should be taken into consideration to determine the appropriate attachment solution for each application. Knowing there are options allows for design flexibility.

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EE-DW Fastner Hdbk K-Blog_SS_Robotics12-21p.indd 1

11/1/21 11:40 AM

Simla Ay

ADhesives: threadlocker

Technical Marketing Writer Hernon Manufacturing

How to choose the ideal threadlocker for an application?

Several different types of threadlockers are available for use, depending on the bolt materials and requirements of the application. For example, blue threadlocker is used for medium-strength assemblies and critical joints that only rarely need disassembly.

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Threadlockers are recommended for use anytime a threaded fastener will be exposed to vibration, repeated impacts, or when it’s imperative to maintain a product’s structure and function. This is because nuts and bolts often loosen due to thermal expansion, vibration, or improper torque.

Although conventional mechanical fasteners, such as nuts or washers, are commonly used to keep the threads secure, mechanical devices are subject to loosening or failure over time.

A chemical threadlocker is a thin, mainly anaerobic adhesive that’s

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applied to the threads of fasteners to prevent them from loosening. It fills the gap between the threads of a nut and bolt, significantly increasing the area of contact, and forming a bonded thermoset plastic seal. This seal ensures unwelcome liquids stay out of the threads and prohibit any penetration of the bolt hole.

The use of threadlocker also increases the area of friction between the mated surfaces. Typically, there’s a range of about 15% metal-to-metal contact between the two (and this is where friction occurs), but the remaining 85% of the threads are not in contact.

In addition to holding the assembly in place, the cured thermoset plastic provides some flexibility to tolerate thermal and cycling while offering an inert barrier that resists galvanic corrosion.

Only a small drop of threadlocker is required for most applications, which is applied near the end of the male threads and away from the bolt head. As a bolt is screwed into a nut or retaining piece, the adhesive will coat the female threads. Once the fastener is fully tightened, the threads will bear down on one another, leaving a small amount of liquid threadlocker as oxygen is pushed out.

This creates an anaerobic environment, given the absence of free oxygen, which triggers threadlocker curing and the threaded assemblies then lock into place.

When choosing a threadlocker, the most important considerations are the: DESIGN WORLD

1. Strength of the adhesive (which is denoted by the color) 2. Fastener size 3. Application methods

•

• 1. The strength Threadlockers are available in a variety of strengths, colors, and grades. The strength is usually denoted by a color.

For example: •

•

•

Purple = low strength. Low-strength bonds can be disassembled using hand tools. This is important when disassembly of an application is a routine occurrence, such as for maintenance reasons.

Blue = medium strength. Mediumstrength assemblies require power tools for disassembly. They’re used for critical joints that only rarely need disassembly.

Red = high strength. High-strength threadlocker is only used for permanent bonds. Disassembly is not easy and requires a combination of high heat and power tools.

2. The size A fastener’s size is an important consideration when choosing the ideal strength and viscosity of the threadlocker required.

Wicking grades, which are typically green, are available to penetrate pre-assembled fasteners.

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•

A low-strength threadlocker is ideal for fasteners that are less than onequarter inch in diameter, such as calibration screws or gauges.

Medium-strength formulations lock fasteners up to three-quarters of an inch in diameter, such as those used in pumps or compressors.

High-strength threadlockers are most often used on fasteners between three-quarters of an inch, up to one inch in diameter. Typically, these are used for heavy-equipment applications.

3. The application If a threadlocker is applied during the assembly of an application, either low, medium, or highstrength grades are used.

However, if a project • requires a threadlocker for parts that are already • assembled, wicking • grades avoid the need • to disassemble and • reassemble all the fasteners.

A wicking threadlocker is a low-viscosity liquid for penetrating and locking pre-assembled parts. It moves between fastened threads by capillary action.

Wicking is associated with the color green to differentiate it from the other strengths available. Localized heating and hand tools are needed for disassembly. It is the go-to threadlocker when fastener disassembly is not an option.

Pre-applied threadlockers are also available. They incorporate a chemical activator through a process called microencapsulation.

Microencapsulation is a method in which tiny amounts of an activating agent are stored within a shell or bead.

The activating material is isolated during storage and released during the assembly process, as shearing the treads burst the beads.

Custom formulas In rare cases, off-the-shelf threadlockers are not ideal for an application. This is typical when temperature extremes are a concern, such as with cryogenic products. It can also occur if the nut and bolt substrates for an application are made of atypical materials or have an unusual shape or coating that will not bond to conventional threadlockers.

In such cases, it’s possible to have a custom formula designed for the application. An experienced adhesive manufacturer can recommend an ideal solution.

The benefits of threadlocker over mechanical locking

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Locks mating threads to prevent loosening from vibration or shock Seals against moisture and fluids Protects against corrosion Prevents fastener galling and seizing Reduces maintenance

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Robert Taylor Product Line Manager ARaymond

A S S E M B LY: F A S T E N E R S

How do I know which threaded fastener is right for my application?

There’s no mathematical equation that will give you the answer to if and when a threaded fastener should be used in an application, but there are guidelines to follow for an educated decision.

Threaded fasteners can be used in any application where a threaded joint is deemed necessary for the proper assembly or continued safe use of a product.

When selecting the ideal threaded fastener for an application, one must consider the: • Loading expectations • Vibration • Risk of failure • Serviceability • Assembly environment • Number of required fastener assemblies

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U-nuts are self-retaining fasteners that provide an easy and fast attachment of mating panels. They will not turn as the screw is driven into place or freeze on screw threads.

The fasteners and load expectations are typically determined by a manufacturer’s R&D department and based on the end product. In some cases, the expected loading is small or the risk of failure so little that threaded fasteners are unnecessary. A non-threaded joint would then be sufficient.

However, when the loading of an application is great and the risk of failure is high, standard nuts and bolts are required.

But what about for the millions of applications used in high-speed assembly environments or that are in the mid-loading range? For example, these are applications that require bolt sizes between #6 screws, 3.5mm in nominal diameter, to M12s or 1/2-inch screws. In

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these instances, self-retaining threaded fasteners are the ideal choice over conventional nuts and bolts.

The benefits of self-retaining threaded fasteners • Available in options to meet loading expectations • Reduce assembly time • Reduce floor space in an assembly plant • Can be installed as part of an assembly • Serviceable To choose the proper self-retaining threaded fasteners for an application, consider the following.

The assembly environment In assembly-line or sub-assembly DESIGN WORLD

stations, one of the threaded-fastener components should be fixed, and this fixed component eliminates the need for two hands or two operators to assemble the component.

The pre-assembled threaded fastener to the fixed component prevents the need to go behind the panel, maximizing the assembly floor space. Additionally, because the fixed nut is superior in screwholding strength, it reduces strip-outs when threading directly into panels.

Self-retained fasteners can also expedite assembly in the field.

The thread type The thread type is largely dependent on the selected screw size.

Some considerations: • • •

Machine screws generally use a tapped barrel or nut retainers Coarse thread screws primarily use u-shaped speed nuts Common screw sizes, such as the M6x1.0, 1/4-20, and #8 (ST 4.2) screws are available in both types

another, have sufficient thickness to withstand loading, and can have two concentric holes punched into them.

However, the panel size and material must be robust enough to handle the loading and vibration.

All u-nuts have a recommended minimum-to-maximum panel range. If the panel is near the high end, insertion efforts will be higher, but the retention will be greater. If the panel is near the low end, the insertion efforts are reduced.

The throat depth is a critical consideration when choosing a u-nut.

It’s defined as the distance from the edge of the panel to the centerline of the hole and is typically 2 mm shorter than the distance from the inside edge of the u-bend to the centerline of the screw receiving feature. If the throat depth is too small, the u-nut will not engage. If it’s too long, the u-nut will hang too far over the edge.

Expansion nuts An expansion nut can be used if the components for assembly are parallel to one another, have sufficient thickness to withstand loading, and can have one rectangular-shaped hole co-centric with a round hole. Like with the u-nut, the panel size and material must be durable enough for the loading and vibration.

The panel thickness is important.

If the part is over the high end, the clip will not engage. If the panel is too thin, the part will rattle. It’s common for the panel thickness to be decided upon after the expansion nut is chosen to “design around the part.” However, the size of the hole must meet the drawing specification for the part to work properly.

Following a few simple guidelines when choosing the proper nut to secure a bolt can ensure a solid, reliable assembly. It can also minimize the assembly time and maximize profits.

Nuts with prevailing (as opposed to non-prevailing) torque are preferred for most joints, particularly when using plastic components or in high-vibration applications. Non-prevailing torque nuts are recommended for joints that have less vibration and loading, or that require frequent disassembly.

The orientation Component orientation is a key determinant when selecting a product family. After considering the screw size, thread type options, and assembly environment, a designer must determine the orientation of the components for assembly.

Every fastener has specific requirements, and some features are more critical, depending on the family selected.

U-nuts A u-nut can be used if the components for assembly are parallel to one DESIGN WORLD

Expansion nuts can provide a fast and vibrationresistant solution when attaching components to blind or center-panel locations where only one side is accessible. They easily snap into rectangular holes and are self-retaining by spring legs.

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Jed Bothell Vice President Atlas UHV

A S S E M B LY: m e t h o d s

What methods are available to bond dissimilar metals for use in critical applications?

Bimetal components do not require bolting or the use of an adhesive. Advanced joining technologies enable engineers to reliably apply the ideal properties of one metal with those of another, offering an advantage in several industries, including the vacuum, cryogenic, and semiconductor sectors, and others.

Where many applications might allow for the use of mechanical bolting or an adhesive or sealant to bond two dissimilar metals, high-performance applications in aerospace, medical, cryogenic, and vacuum often require greater strength and longevity.

Mechanical fasteners are ideal for several applications but are subject to cracking or corrosion, depending on the environment, and add weight to an assembly. Adhesives provide a solid bond at the beginning of use, but they typically degrade over time.

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Additionally, the process of joining certain materials, such as aluminum to other metals, is challenging. Its tenacious oxide surface protects it from rust-like oxidation, which is visible on iron and steel, preventing close metal-to-metal contact.

Fortunately, there are alternative methods for bonding dissimilar metals that ensure a solid bond.

The two most recognized methods are explosion bonding (or explosion welding) and diffusion bonding. Each one offers benefits and drawbacks, depending on the application. But both DESIGN WORLD

In the explosion bonding process, the EXW bond line separates the aluminum portion of a component from the stainlesssteel part, as shown above.

methods produce a molecular bond that outperforms mechanical bolting and adhesive bonding, which typically require upkeep and maintenance.

Explosion bonding or welding (EXW) is a solid-state process by which dissimilar metals can be joined together at an atomic level. Preparation for bonding requires that two plates lay flat against one another — a flyer plate on top of a base plate, separated by a small gap. An explosive charge is placed on the flyer plate and detonated from a point at the edge of the plates.

A controlled progressive ignition travels across the flyer plate much like ripples in a pond. The explosion accelerates the plates together with impact velocities of 1800 to 2200 m/sec.

As a result, a high-energy surface plasma DESIGN WORLD

is formed between the plates, moving ahead of the collision point and stripping electrons from the two bonding surfaces.

The electron-hungry metals are then thrust together at extreme pressures, forming an electron-sharing bond.

Metals — such as copper, titanium, high-nickel alloys, and stainless steel — can easily be bonded through the EXW process. Typically, aluminum and stainless steel are incompatible and unable to bond directly, because of the formation of brittle intermetallic compounds.

However, technology is solving this challenge. One solution exploits the metallurgical compatibility from a multi-layered composition consisting of 316L stainless steel, copper, titanium, and 6061 T6 aluminum to provide a part with maximum hermeticity (or airtight), ductility, and an ability to cycle from cryogenic to high temperatures.

EXW is not always ideal. It depends on the final application. Depending on the bonding materials, explosive bonding typically requires a metal layer between the two primary metals, such as copper. This layer must be evaluated when producing a part because it also has characteristics that might affect www.fastenerengineering.com

the final application. For example, a copper substrate will add an electrically conductive layer to the end product.

Diffusion bonding is a process by which different metals are placed together at an extremely high pressure and heated to an elevated temperature for a specific duration. Bonding occurs in stages.

First, the materials yield and creep in a way that the frictional force pushes waves of the now plastically deformed materials into a larger area of contact.

Atoms that are in the contact area, then, diffuse and rearrange the grain boundaries of the two materials in such a way that it eliminates the original pores in the bonded area.

Finally, this diffusion dominates the area, forming a bond. It’s critical, however, that surface oxides are removed or displaced, which typically necessitates a vacuum environment.

It’s also important to note that diffusion bonding has machine limitations. This type of bonding depends on the strict control of bonding pressure, bonding temperature, the atmosphere, and the holding time. These conditions vary for bonding different materials. Aluminum stainless bonds are particularly challenging as a result of the formation of brittle intermetallic compounds, which can weaken the bond.

Additionally, thickness restrictions based on a machine’s size might create part size limitations. The joining of dissimilar metal parts requires a unique set of skills to properly machine the joined materials into a useable assembly.

So, it’s important to work with reputable engineers or experts in the field.

A benefit of reliably bonded bimetallic joints is that these assemblies can be used to combine corrosion resistance, higher thermal conductivity, and several other properties not found in just one metal. With bimetallic joints, engineers can make a metallic composite material that enables them to attain the highest performance and maximum value.

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bolts

When does an application warrant the use of a bolt instead of a screw?

Screws and bolts are the most commonly used mechanical fasteners.

Although similar and sometimes referred to interchangeably, screws and bolts offer unique features and are ideal for different applications.

A screw is an externally threaded fastener, typically used to assemble objects with threads. A bolt, on the other hand, is used to assemble unthreaded objects and usually with the use of a nut. Unlike some screws, bolts are not self-tapping and are only partially threaded. A self-tapping

fastener is one that can tap its own hole as it is driven into the material.

Screws (if self-tapping) are designed to be installed in a pre-drilled or pilot hole, or (if self-drilling) can tap their own hole during installation — thanks to a sharp, drill-bit point and full threading.

Most significantly, screws do not use a nut to retain the assembly. For this reason, they’re shorter than the width of the fastened part and do not protrude through to the other side. It’s the friction at the threads, which is the force that keeps the parts securely fastened.

The most common type of bolt is the hex bolt. It has a hexagonally shaped head, providing a flat surface for tools to apply torque during fastening.

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December 2021 www.fastenerengineering.com

DESIGN WORLD

Bolts are slightly different in the way they fasten an assembly. The hole for a bolt is untapped. Instead, the bolt is pushed through the hole and fastened using a nut at the back of the assembled part. Therefore, a bolt is longer than the width of this part and protrudes for the nut to screw onto the other side.

The unthreaded portion of the bolt remains unseen and in the assembled part.

It’s what provides an advantage over most screws. Typically, bolts are selected for an application because they add strength, making the assembled parts more resistant to shear forces when compared to fully threaded screws. Compared to screws, they offer far more holding power.

A washer is also often used with a bolt and nut to spread the load over a larger surface area, thereby reducing stress and wear and tear that might otherwise loosen the bolt over time.

Bolts are installed or removed using a handheld or pneumatic wrench (screws, of course, use a screwdriver or drill bit).

The benefit of a pneumatic wrench is that it provides more torque than a handheld tool, which makes the task easier.

Banking on bolts Generally, screws are used when basic or medium-holding power is required, such as for sheet metal, plywood, drywall, pressboard, deck planks, etc. The reliability of screws is moderate.

Bolts are the go-to choice for heavyduty applications and are a reliable choice for use with concrete, beams, and studs.

This is because the nut and bolt assembly creates a high clamping force, keeping two parts fastened under compression.

When a load is placed solely on a bolt, it’s limited to the amount that it can handle before failing. However, when a bolt is tightened against the material of the part to be fastened, it distributes the force throughout the part. This means the bolt only holds a portion of the load — which is important with heavy applications, otherwise, the bolt might fail.

Essentially, the threads of the nut work with those of the bolt to apply force

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to either side of the fastened material. This tension, or compression force, is referred to as the bolt preload. Preload is important because a properly installed bolt assembly can withstand a much heavier load without the risk of fastener failure.

There are a few ways to ensure bolt preload. For example, there are preload-indicating washers that spin until a certain amount of load is applied to them. When the washer stops spinning, the preload has been met. There are also direct tension indicating washers, which have tiny, raised bumps that flatten when the preload has been achieved Torque is also significant. A quality torque wrench can also indicate the optimal torque, which should typically be in close range to the ideal preload.

Getting the grade Much like any fastener, bolts and nuts are available in a variety of sizes, types, and material options. Steel bolts are the most common. The ideal choice will depend on the application. First assess the type of material to be joined, its thickness, and the weight and strength requirements.

Bolt grade markings, which typically appear on the head of the bolt, should www.fastenerengineering.com

Bolts are graded according to their strength, using two numbers separated by a point, that are stamped onto the bolt head. The first number before the point is the ultimate tensile strength (UTS) in MPa, divided by 100. The second number is the ratio of yield strength to the UTS. Common classes are 5.8, 8.8, and 10.9. For example, a grade 8.8 bolt has a UTS, the load at which it would fail, of 800 MPa and will yield at 80% of this value (640 MPa).

be referred to and serve to indicate the minimum acceptable standard of mechanical properties or performance that the fastener must meet. Higher grades offer greater mechanical strength.

For commonly used ASTM and SAE steel grades, there are grade identification tables for the commonly used grades (ASTM and SAE), which specify the minimum acceptable values of proof, tensile, and yield strength, etc.

In summary, bolts are used for fastening unthreaded parts whereas screws are used for threaded parts. Bolts provide a much greater holding strength and are preferred for use in high, loadbearing applications. However, this also means bolts typically cost more and require a nut (and usually a washer) for secure fastening.

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William Hewitson President Ruland Manufacturing Co., Inc.

couplings

How to avoid coupling failures?

Mechanical couplings have a principal use in the connection of rotating shafts for the transfer of rotary motion and torque. As with all mechanical devices, a coupling must match its intended purpose and application parameters including various performance, environmental, use, and service factors.

When selected with these design parameters in mind — and when installed and maintained correctly — a coupling should have no failure issues over its lifetime. However, if these design parameters are not adequately met, a coupling can fail prematurely. The result might be negligible and a small inconvenience; or it might be far more significant and include financial loss or personal injury so due diligence is critical.

Here are a few of the primary reasons why couplings perform poorly or unsuccessfully, along with the steps that can be taken to minimize failure risk.

Coupling errors Ideally, a coupling must fit its intended application, meeting the required performance factors. However, a design engineer must also consider additional criteria and address issues relating to the application environment (for example, heat, cold, vibration, humidity, debris, etc.), serviceability, and potential maintenance requirements.

One key is to think ahead. The availability of a new coupling for future replacement if or when necessary should be planned for in advance. Preparation is critical as downtime can seriously affect many processes, leading to lost uptime and revenue.

A common mistake in design selection is an incomplete understanding of what the manufacturers’ product specifications mean. For instance, when the manufacturer provides torque data,

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At work and working properly: three types of Ruland couplings on shafts (from top to bottom): bellows, beam, and Oldham couplings.

carefully review how it’s stated and if there are other service factors to consider. Jawtype couplings are typically expressed with an operating and peak torque to account for use in start/stop applications. But this differs from beam couplings, which are usually expressed using static torque and derated based on use.

A designer must fully understand these specifications and the design criteria for the system or application under review to select the ideal coupling. Another common mistake is mismatching the coupling to the equipment’s misalignment condition. The goal of shaft alignment is to increase the reliability of rotating machinery. However, misalignment is not uncommon.

For example, with parallel misalignment, the center lines of both shafts are parallel, but they are offset.

Angular misalignment is the opposite,

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where the shafts are not in the same horizontal or vertical planes.

These are important distinctions, and the proper selection of a coupling cannot be made correctly without an overview of the application and an understanding of the misalignment issue being addressed in the system. The goal of ensuring alignment is to increase the reliability of rotating machinery.

Consequences A mismatched coupling for a given application can have several consequences.

When one or more of the design criteria and overall system attributes are not met, a coupling is likely to fail. Coupling failure can lead to equipment downtime, unplanned maintenance, financial loss, or more serious human injury.

Mechanical couplings are typically used for connecting rotating equipment shafts for the transfer of motion and DESIGN WORLD

torque. A coupling choice that does not accurately account for the torque requirements, including the starting and stopping torque as in servo-motor applications, can result in failure and potentially harmful consequences.

When shaft misalignment is a design factor, a beam coupling is usually a good performance and economic choice. Beam couplings are ideal for handling angular misalignment and axial motion. However, failure may occur in applications with parallel misalignment. This is because the single beam must bend in two different directions simultaneously, creating larger stresses in the coupling.

When excessive parallel misalignment exists in the application other types of couplings should be considered, such as bellows and Oldham, subject to the system design criteria.

Choosing wisely Choosing a coupling for an application can be a complex process but should not be overly time-consuming. The best advice is to carefully consider all of the system design criteria.

Typically, these include: torque, shaft misalignment, stiffness, rpm, inertia, space requirements, shaft mounting, and there are others.

Selecting the ideal coupling is not the end of the job. It’s equally important to install it properly, verifying that the design considerations were followed and correct for the application. For example, there might be a greater or lesser degree of misalignment than originally specified.

Additionally, ensure that the

application assembly is regularly maintained so that the design parameters are up to par. It’s important that no system component or coupling wear, contamination, or other detrimental factors have been introduced into the assembly.

How to maximize production and minimize coupling failures?

When specifying and installing a coupling, ask these questions…

• What are the accuracy requirements?

• Does the application require high torsional stiffness?

• Is dampening or shock absorption necessary? What about electrical isolation?

• How much misalignment is present in the design? Is it angular, parallel, axial, and/or complex?

• Does the coupling need to be fail-safe?

• What speed and temperature will the coupling be operating at?

• What is the maximum torque that will be applied to the coupling?

• Are there other environmental factors to consider for the application?

Far too often motion control couplings are selected exceedingly late in the application design process. Yet, these components are critical to successful system performance.

Early selection will reduce errors along with the potential for premature coupling failure.

The keys to avoiding coupling failure are correct coupling selection based on the design parameters, proper installation, and periodic system maintenance.

To learn more, go to tinyurl.com/ MechanicalCouplings

A beam coupling has failed near the center, representing what can occur in a torqueoverload condition.

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December 2021

17

Jonathan Coulter Commercial Product Manager Southco, Inc.

latches

Latches, such as this C2 Lever Compression Latch, can offer a streamlined look that’s easy to install and operate while ensuring a secure and sealed fit.

What are the different types of latches available for secure enclosures?

A latch is a mechanical device that joins two objects together while allowing for regular separation or autonomy. For example, these two objects can be a moving panel or door, and a non-moving or fixed panel.

A latch typically holds these objects together to protect the contents of an enclosure, granting regular access when needed — such as a metal latch that might hold a gate closed when not in use. Choosing the ideal latch, which appropriately manages access to an enclosure, is an important consideration during the design process.

Latches range greatly in complexity, depending on the purpose of an intended application. There are several factors affecting latch selection, including the:

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• • • • •

Actuation method Ease of access Desired mounting style Security requirements Environmental considerations

Design engineers should carefully consider these factors when deciding which type of latch to select for their specific application.

Types of latches The following latch types can be used to manage access to enclosures.

Cam latch – consists of a body that’s typically attached to a moving panel or door, which incorporates a cam lever that can be rotated to engage a nonmoving or fixed panel. Once the door www.fastenerengineering.com

is closed, the cam rotates behind the fixed panel to secure the moving panel or door. The cam lever is actuated by a simple twisting or turning motion, either by hand or tool.

Compression latch – nearly identical in functionality to a cam latch in that a compression latch is composed of a body and a cam lever that rotates when actuated by hand or tool. However, with a compression latch, the cam creates a clamping force between the two surfaces.

This force between the panels helps prevent vibration or rattling. It can also compress a gasket to provide adequate sealing for protection against environmental factors, such as dust or moisture.

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Today, there are several latch options that offer quick accessibility, smooth operation, and vibration-resistant fastening — and in a variety of styles including hand-actuated, toolactuated, or key-locking.

For example, the E5 Cam Latch series from Southco provides quick access with just a quarter-turn. Its modular design is ideal for several different actuation and door dimensions.

Draw latch – provides compression by pulling two surfaces securely together in the same plane while reducing vibration or rattling. A draw latch is typically made up of two parts. The first is attached to one panel and acts as an operating mechanism.

The second panel has a mounted securing part or mechanism, which acts as a keeper.

Tension is, then, created when the lever is hooked to the keeper.

Outdoor latching – have stricter requirements compared to indoor latches. This is because engineers have to account for environmental factors and weather events when designing outdoor latches, such as cold weather, ice, or heat and high humidity.

Depending on the application, corrosion resistance and material degradation might also be necessary design considerations. Latches used in electrical and food equipment often need to meet specific industry requirements for design, construction, or sealing.

It may be necessary to meet certain specifications, such as with the National Electrical Manufacturers Association (or NEMA, which designs standards in North America for electrical enclosures) and the Underwriters Laboratories (or UL, a global safety certification company), or other organizations.

When a latch is installed outdoors, security risks increase depending on the location and its interior contents. Typically, outdoor latches are constructed of strong or durable DESIGN WORLD

materials, such as stainless steel, and offer sophisticated locking mechanisms designed for better security.

Push-to-close or slam latch – holds doors or panels securely, allowing closure by simply pushing the door closed. This type of latch, when attached to a swinging door or panel, consists of a body and a cam that’s spring-loaded.

When the panel or door is closed, the cam is either pushed in against a mating surface or it hooks around a striker.

Then, the cam will spring back out behind the mating surface or lock around the striker to secure the panel or door in place. The push-to-close is sometimes referred to as a “slam latch” because of

its ability to resist damage if the door or panel is slammed shut. Unlike many other latches, the handle requires no turning for the latch to engage.

Sliding latch – made up of a sliding or rotating body that’s attached to one surface and a stationary keeper that’s attached to the other surface. The two surfaces become secure when the sliding or rotating mechanism moves behind the more stable part. Slide latches can also be designed to resist vibration and rattling.

Visible or hidden latches – choosing a hidden or visible latch will depend on the end user’s requirements and operating environment.

Visible latches are important when a user must view the latch to actuate it.

Hidden latches are generally required for security reasons, in which case they can be concealed behind a door or panel. Hidden latches also allow for clean, uninterrupted surfaces, which can improve the appearance of a product or piece of equipment.

Ideally, evaluate an application’s requirements, features, and environmental considerations early in the design process to ensure the best latch for the job.

Draw latches should offer a tight latch grip and additional clamping force for doors and panels in challenging outdoor operating conditions. Southco’s 37 Lever-Assist Latch features a long handle for added leverage and built-in detents to prevent accidental opening due to shock or vibration.

www.fastenerengineering.com

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19

Article courtesy of UC Components

manufacturing

Vacuum chambers must remain clean and free of contaminants and volatile materials that could lead to contamination of the entire system — and this includes the fasteners used in its assembly.

How fasteners can affect product testing and manufacturing?

Manufacturers in a range of industries rely on vacuum chambers for different phases of product development, testing, and final manufacturing.

Vacuum chambers work by removing air and gases from a vessel or chamber through a vacuum pump — creating a space (or vacuum) that’s completely devoid of matter.

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These chambers must remain clean and free of contaminants and volatile materials that would disrupt the entire system. Cleanliness is incredibly important. Anything that exists within a vacuum system that hurts or inhibits its proper function is a contaminant and must be addressed. This can include the fasteners.

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In fact, O-rings are most often the primary source of contamination in any vacuum system. An unprocessed O-ring contains a great deal of water, which is chemically formed during the manufacturing process.

Additionally, the materials used for any of the fasteners — including during post-fabrication treatments — are vital, particularly if the fastener will be exposed to corrosive elements, extreme temperatures, extreme pressure, or high levels of physical strain.

High and ultra-high vacuum applications require parts that are free from volatile materials that would lead to contamination of the vacuum system.

Types of contamination issues include • • • • •

to the surface, machining, tooling for drawing, rolling, and heading.

For example, the material that the fasteners are manufactured from, or coated with, can potentially release lightweight molecules that can interfere with the vacuum process. This is also true for materials that are not normally considered absorbent, such as metals and glass.

Mild steel parts are often chromeplated or black-oxide-coated to prevent rusting. These types of rust or corrosionpreventing methods should be carefully vetted for their appropriateness for vacuum service.

Particles are another, more direct form of surface contamination and should be factored in when choosing the type, coating, and use specifications.

Imbedded and surface water Surface particulate Volatile organics Hydrocarbons And other types of debris

All types of packaging can also impart contamination to the parts contained within. Even handling a properly cleaned part with bare hands can impart skin oils that will also outgas and drag a system down, emphasizing the need for gloved hands and the proper handling of a cleaned fastener.

How to address contamination problems?

Vented screws (also known as vacuum, ventilation, or hollow screws) and/or vacuum baking are two methods that can address potential contamination issues.

A vented screw features a hollow core, which is specifically designed to allow the release of gases, contaminants, and pressure through the fastener. These types of screws are widely used within vacuum

Vented screws feature a hollow core, which rapidly eliminates trapped air volumes from the base of the screw during pump-down when used within a vacuum system, ensuring a clean environment. Learn more in this video: tinyurl.com/VentedScrews

All of these can lead to virtual leaks, outgassing, and other catastrophic issues within a sealed, vacuum system.

Similar problems can also occur if using improper or misspecified fasteners.

What are the sources of vacuum contamination from fasteners?

Fasteners can lead to several contamination issues due to: • • • • • •

The materials they’re made from Secondary treatments, such as coatings or use of lubricants Improper cleaning and/or incorrect packaging of the fastener(s) Mishandling, such as carrying fastener(s) by hand after cleaning Using the wrong type of fastener in a blind-tapped hole And others

Surface contamination in a vacuum system can come from a variety of sources — starting with the original metal the fasteners were made from. This includes any wire or lubricants added DESIGN WORLD

Plastics, elastomers, porous metals, ceramics, and lubricants are some of the worst sources of material outgassing.

Vapor pressure and the rate of chemical reactions at higher temperatures can also cause outgassing.

Hydrocarbon-based lubricants can also be a major source of contamination and are difficult to remove. Secondary hydrocarbon-based lubricants (such as oils and grease) can be major and destructive forms of contamination in vacuum systems because they have a low vapor pressure and will spread throughout a tool quickly, requiring lengthy and costly cleaning to remove properly. www.fastenerengineering.com

systems and allow for the quick evacuation of trapped pockets of air and surface contaminants from blind-tapped holes.

Vacuum baking provides the ultimate level of contamination control for fasteners in extremely critical process environments. The vacuum baking cycle can be monitored and certified with a residual gas analyzer, which provides control and monitoring to ensure a contaminate-free product.

Overall, careful selection of the fasteners, as well as proper cleaning, packaging, and handling of fasteners after cleaning, will ultimately offer the best product for your vacuum system.

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Barbara Gerard CEO Craftech Industries, Inc.

materials

What type of plastic is ideal for high-performance fasteners?

Polyoxymethylene (POM) is supplied in a granulated form and, with heat and pressure, can be molded into the desired shape. It offers strength and hardness, making POM plastic an ideal choice for many fastener applications.

Metal has long been the material of choice for mechanical fasteners.

However, it’s no longer the go-to option for all design engineers. Depending on the application, the use of plastic is gaining popularity and offers several material advantages including strength, longevity, and cost-effectiveness.

Plastic fasteners are now more frequently used in high-pressure and critical environments. Much like with metals, plastics offer different properties and options — such as nylon, polyvinyl chloride (PVC), polyoxymethylene (POM), and others. The choice should be based on the demands of the application and its environment.

For example, nylon is a popular choice and works fine for everyday

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wear and tear. PVC is often ideal when corrosion and weather-resistance are required. For high-performance, however, you’ll want to consider POM. Precision parts Polyoxymethylene is an engineering material used in parts that require precision. Applications for POM include high-performance components, such as fasteners (screws, nuts, washers, etc.).

The material is ideal for parts that require high strength, stability, durability, and low friction. It’s also used in a variety of other applications, such as for zippers, ski bindings, insulin pens, coffee spigots, and even as a solvent for perfumes and as a synthetic flavoring ingredient. www.fastenerengineering.com

POM is a thermoplastic material also known as acetal. It’s a molecule containing the functional group of carbon bonded to two –OR groups and was first discovered by a German chemist, Hermann Staudinger, who won the 1953 Nobel Prize in Chemistry.

Staudinger had studied this material in the 1920s but found it to be thermally unstable. This thermal instability meant the material was not useful, at least not commercially.

Eventually, however, a heat-stable POM homopolymer was discovered by the chemist, Dal Nagore. He realized that by reacting the hemiacetal ends with acetic anhydride, he could readily depolymerize hemiacetal into a thermally stable and melt-processable thermoplastic.

Soon after, the chemical company DuPont synthesized a version and filed for patent protection of the homopolymer. In 1960, it built a manufacturing plant to produce Delrin — its version of the POM homopolymer, which is still offered today. Around the same time, the chemical company Celanese completed its study of the copolymer and started production of Celcon.

Other manufacturers soon followed with their versions of this material.

The process It’s important to note that different manufacturing processes are used to produce the homopolymer and the copolymer versions of POM. To make the homopolymer, first anhydrous formaldehyde is necessary. The formaldehyde is then polymerized by anionic catalysis and the resulting polymer is stabilized by the reaction to acetic anhydride.

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The water that’s produced must be removed from the reaction. The homopolymer has excellent creep resistance. For example, DuPont’s Delrin is typically made this way. However, the copolymer of POM requires that the formaldehyde is converted to trioxane, which can be done by acid catalysis. This is followed by purification of the trioxane by distillation or extraction to remove the water and other active impurities containing hydrogen.

Thermoplastic benefits The benefits of thermoplastic parts include an ability to provide strength and corrosion resistance, typically lowering maintenance and repair costs and extending longevity. This is why design engineers are now often choosing plastics over metal parts.

Plastic is more resistant to normal weather conditions and some extreme environments, resulting in less maintenance and fatigue over the long run. Not only will plastic fasteners last longer, for example, but they also offer higher-temperature thresholds, are less subject to vibration, and provide enhanced operational efficiency and reliability.

What’s more is metal parts tend to weigh more than plastic parts, which can make it more difficult to transport and install when compared to plastic.

Polyoxymethylene demonstrates the following properties: • • • • • • • • • • • •

High stiffness Low coefficient of friction Hardness and durability High abrasion resistance High heat resistance Low water absorption Good electrical and dielectric properties Excellent dimensional stability More creep resistance than nylon Low smoke emissions A high-gloss surface Highly crystalline

There are drawbacks to the use of POM, depending on the application. Although this material offers high heat resistance, it’s unavailable in a flame-retardant grade. It also has poor resistance to acids and a high shrinkage rate.

The key is to choose the right material for your fastener application. Fortunately, there is more than one type of plastic available — some can be machined, others molded, and some are as strong as stainless steel. The type selected is critical because it will affect the function, longevity, appearance, and cost of the project.

As with any important purchase, choosing a knowledgeable supplier for plastic components is critical. Look for one with insight into the different materials available for fasteners that can offer strong technical support.

Whether it’s extreme temperatures, vibration, or chemicals, it’s important to consider the elements fasteners will be exposed to before choosing the ideal type and material that works best for an application.

For example, POM is commonly used in the consumer electronics and automotive industries.

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December 2021

23

NUTS

What are twin nuts and how do they function?

A nut is a mechanical fastener with a threaded hole. It’s used with a bolt, screw, or stud to provide a clamping force and prevent axial movement.

Typically, a bolt is inserted through two parts with aligned holes and a nut is then screwed onto the bolt.

The shaft of the bolt prevents radial movement of the parts while both the head of the bolt and the nut prevent axial movement.

The most common type of nut is the hex nut. It has a hexagonal outer shape for the faces of tools to apply torque when fastening.

The hex nut is typically TWIN OR SPLIT NUTS ARE a good go-to option for many basic assemblies.

IDEAL FOR APPLICATIONS THAT However, there are also several types of nuts REQUIRE THE ADDITION OF A available to suit the needs of different applications.

STRUCTURAL NUT TO ANY BOLT, One such option is the twin nut, which is ROD, OR THREADED SHAFT a type of split nut that resembles a regular WHERE THERE’S NO ACCESS TO hex nut that’s cut into two pieces for quick THE OTHER END OF THE PART. assembly and rapid adjustment. The two halves lock together so that they can function as a typical nut. To secure the nut to a bolt, it’s typically fitted with a conical washer.

Twin or split nuts are ideal for applications that require the addition of a structural nut to any bolt, rod, or A twin nut is a unique type of fastener that can be split into two halves for quick assembly or adjustments of an application.

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threaded shaft where there’s no access to the other end of the part. Installation on a bolt, rod, or shaft can be done without the disassembly of these fasteners.

The split feature of the twin nut means it splits into two, identical halves along a plane that passes through the axis of rotation. This allows the female thread to be opened and placed around the male thread. It can, then, be used to insert the nut onto a leadscrew, which has no accessible end.

Alternatively, this allows the nut to be opened so that it can move axially along a screw without any relative rotation — and then closed at a new position (so that the screw actuation can resume). This can be useful in positioning applications, such as the leadscrew of a lathe, allowing a quick, rough setting before the final adjustments are made.

Split nuts used in these types of positioning applications are usually made with machined parts and have additional mounting interfaces for secure attachment. They typically have threads cut to match the leadscrew of the machine. For this reason, these fasteners can be more costly to manufacture.

The ability to separate the nut and place it at an arbitrary location and along a long, threaded shaft can be particularly useful for clamping and tooling adjustment operations.

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Advantages of twin (split) nuts: • Easy to install • Disassembly of the bolt or shaft is not required • Greater inherent strength • Improved thread load distribution • Reduced tensile bending stress and bending at the thread root

The simple installation of a wing nut — no tools are required.

The term, “twin nuts,” can also refer to the combination of a jam or half nut that’s used with a regular nut and as a form of friction (like a lock nut).

A jam nut is typically used when it’s necessary to lock a nut into place without clamping to another object.

It’s used to resist loosening under vibration and torque.

Take your pick Nuts are the mating part in the assembly of a bolt and are used in many different applications, from basic furniture assembly to complex automotive or aerospace requirements and many others.

There are several types of nuts available, including specialty options, depending on the application. Consult with your fastener supplier to determine the ideal choice for your application. Here are a few options: Barrel or dowel nut: has a cylindrical shape that can be inserted into a hole, which runs perpendicular to the axis of the bolt.

Cage nut: a type of captive nut that can be attached to thin materials, such as sheet metal, allowing bolts to be fastened in inaccessible spaces.

Cap nut: also called an acorn nut (because of its shape), it has a domed top to prevent contact with external threads.

Castellated nut: works as a locking device that’s resistant to movement and vibration and can be readily removed. Also called a castle or slotted nut, it’s typically used with cotter pins to prevent loosening.

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Coupling nut: an elongated nut that allows two threaded shafts to be joined coaxially.

Flange nut: has a wide flange at one end, which serves as an integrated washer to prevent movement. Serrated flanges work to distribute force or pressure on the nut over the part being secured and ensure a locking action.

Keps or k-nut: designed to make assembly easier, it includes an attached free-spinning, lock washer.

Knurled nut: has a large textured (or “knurled”) diameter and is designed to be hand-tightened.

Square nut: a four-sided (square) nut that may be flat or beveled on top, providing a greater surface contact area — which offers greater resistance to loosening.

T-nut: used to fasten wood or particle board, it has a thin body with a flange at one end that resembles a “T.” Wing nut: has two “wings” on each side, which allow it to be easily tightened and loosened by hand without tools.

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25

Jeff Greenwood

PINS

Product Sales Engineer SPIROL International Corporation

COILED SPRING PIN SLOTTED SPRING PIN

HEADED, BARBED SOLID PIN

How to select the proper pin for an application?

Fasteners are some of the most important parts of an assembly as they hold all of the parts together and facilitate any interaction between the components. Ideally, the selected fasteners are simple to install, provide a quality product for the lifetime of the assembly, TYPICAL PIN FUNCTIONS and yield the overall lowest cost given the entire manufacturing process.

Coiled pin Slotted pin Solid pin Press-fit pins are one Hinge (free fit) X X X of the most common Hinge (friction fit) X types of pins used in Hub/shaft X X X modern manufacturing.

The fasteners are typically Alignment X X X easy to install and let Stop X X X manufacturers avoid Joining X X X soldering, such as when Serviceable X X assembling electronics.

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There are two general categories of press-fit pins: solid and spring pins.

Solid pins either have a smooth, uninterrupted surface (such as dowels) or are designed with retention features (such as knurls, grooves, and barbs). All solid pins are retained by displacing the host material.

Conversely, spring pins are selfretained by exerting a radial force (tension) against the hole wall after installation.

There are two different types of spring pins: slotted spring and coiled spring pins.

Slotted spring pins are general-purpose fasteners typically recommended for noncritical assemblies. Oftentimes, these pins are used in applications where they’re manually installed into mild or hardened steel components. They have a gap designed for the pin to flex during installation, which lets it absorb the varying hole tolerance.

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Coiled spring pins are available in light, standard, and heavy-duty options, so a designer can choose the optimum combination of strength, flexibility, and diameter suited for varying host materials and performance requirements. These pins have two, 1/4-coils of material, allowing them to flex during and after installation. The flex supports varying hole tolerances, helps dampen shock and vibration, and prevents hole damage.

Common functions Although there are several ways to use pins, the most common are shown in the Typical pin functions table. These guidelines apply the majority of the time, but each application should be evaluated for which pin type is most appropriate.

Choosing right These are some of the many considerations when determining the proper pin for an application: • What’s the pin’s function?

• What are the strength requirements of the pin?

• What is the material of the component in which the pin will be used?

• What environment will the pin be exposed to?

• What’s the intended product lifetime or the number of cycles?

• How will the pin be installed?

Spring pins are typically preferred over solid pins because of their flexibility, lower insertion forces, and ability to accommodate wider hole tolerances.

However, there are exceptions.

Solid pins are the ideal choice when precise hole locations must be maintained, it’s necessary to manually align several clearance holes, a hollow pin is unsuitable, or increased bending or shear strength is required. Solid pins are also favored when a smooth, uninterrupted surface is preferred (such as when used in conjunction with an angular component) or the head is required for a positive stop or to retain a thinner part to a thicker section of an assembly.

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Coiled spring pins are superior for assemblies that are subject to dynamic loading. This is because these pins offer a unique combination of strength and flexibility, which allows them to dampen forces and vibration, preventing hole damage and prolonging the assembly life.

Each type of press-fit pin serves a purpose for manufacturers. The Features and benefits table compares the common features, advantages, and benefits for each type of pin.

FEATURES AND BENEFITS

Coiled pin

Slotted pin

Flexes to prevent hole damange during installation

X

X

Allows for wide hole tolerances

X

X

Superior combination of strength and flexibility

X

Superior performance in static applications

X

Superior performance in dynamic applications (absorbs shock loads)

X

Solid pin

X

X

Superior resistance to axial load (push- out/pull-out)

X

Tamper-resistant X Performance in soft materials under static X loading (with aluminum, plastic, etc.)

X

Provides positive stop/location

X

X

X

Designers can optimize the performance and total manufactured cost of an assembly by selecting the proper pin for an application. To do so, the fastener options must be considered early in the design stage of a project.

One of the most important steps in selecting the ideal pin is to fully evaluate and establish the performance requirements of the intended applications. The design team should also test and validate the fasteners in prototype assemblies before a final decision is made. www.fastenerengineering.com

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Article courtesy of Rotor Clip

RINGS

What are the technical factors to consider before choosing retaining rings for an assembly?

Much like a screw requires a correctly tapped hole, retaining rings need properly cut grooves for high-quality performance. Both grooved walls should be parallel and perpendicular to the axis of the shaft or housing.

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It’s challenging to develop economical designs that reduce weight, size, raw materials, labor, and costs. Retaining rings hold components in place while accomplishing these goals.

Retaining rings are metal fasteners that secure components or assemblies onto a shaft or in a housing or bore.

Essentially, these devices keep parts in place using a compact design that requires fewer machining operations than other fastening techniques.

Like most fasteners, retaining rings can range in size (from 1 mm to 1 m in diameter) and are available in different combinations of size, shape, style, and material. However, knowing which ring is ideal for an application will contribute to the overall effectiveness and economy of the design. www.fastenerengineering.com

Here are some factors to consider before choosing a retaining ring for an assembly.

Groove depth and preparation Retaining rings are installed into a groove on a shaft or bore and, therefore, should fit the specific grooves to perform as designed. The grooved walls should be parallel to one another, yet perpendicular to the axis of the shaft or housing.

When a load is applied, it creates a lever action against the loaded, grooved wall. Under extreme loads, this can lead to a deflection of the ring and, ultimately, failure. Failure is far more likely to occur if the incorrect ring is used for the application.

Standard or inverted lugs Before settling on a retaining ring style, DESIGN WORLD

Inverted retaining ring designs mean the lugs do not stick out from the shaft, allowing for greater clearance.

it’s important to assess the demands of the application. For example, if the loading conditions of an application call for maximum groove engagement, standard retaining rings are generally an ideal choice.

However, if the force or load of an application is not a critical factor, preference should be given to inverted rings — and particularly when lug protrusion might cause an interference challenge. The lug is the part that protrudes from the ring, often containing lug holes, which are used for installation and removal. Since they protrude, the lugs can get in the way.

But this is no problem for inverted lugs as they allow for greater clearance.

Inverted ring designs are also often used in low-load capacity applications where aesthetics or compatibility are the main criteria. Otherwise, these two styles are interchangeable as far as the groove dimension is concerned.

Beveled retaining rings offer the cost-saving benefits of conventional rings with an added advantage: they compensate for accumulated tolerances or wear in the retained parts and provide rigid endplay take-up in the assembly.

Basic versus heavy-duty To ensure reliability in applications with significant loads, a reinforced retaining ring will typically outperform a nonheavy type. This is because of the larger section, lug shape, and thickness of the DESIGN WORLD

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RINGS

Self-locking or push-on retaining rings offer easy installation and security in one solution. They’re suitable for devices with shaft or housing diameters of one inch or less that require low thrust loads.

reinforced ring, which is better able to remedy instances of fatigue failure.

For radially installed retaining rings, where space is at a premium and loads are small, a crescent C-ring is usually the best choice.

E-clips are a kind of shaft-mounted retaining ring, which are ideal for use with higher loads as they offer a larger abutment area for retaining. Reinforced E-rings function best in applications characterized by high vibration, or with RPM and cyclic loads.

Bowed and beveled retaining rings Retaining rings can offer multiple advantages, depending on the type.

They can be used to compensate for

IN MANY ASSEMBLIES, DIMENSIONAL TOLERANCES IN RING THICKNESS, GROOVE LOCATION, OR THE OVERALL LENGTH OF THE COMPONENTS BEING RETAINED ADD UP TO A DEGREE OF CLEARANCE — OR ENDPLAY — BETWEEN THE ABUTTING SURFACES OF THE RING AND RETAINED PART. 30

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any accumulated tolerances or wear in an assembly and can exert pressure between and against retained parts.

Bowed rings, for instance, can flatten under specified loads and will return to their original height when the application’s load is decreased and removed. When the ring is flat, it exerts a counter-load much like a spring, offering endplay take-up and producing a compressive force that reduces chatter and vibration.

In many assemblies, dimensional tolerances in ring thickness, groove location, or the overall length of the components being retained add up to a degree of clearance — or endplay — between the abutting surfaces of the ring and retained part. The endplay can sometimes be eliminated by shims, washers, or similar components by “selective assembly” in which the parts (with plus or minus tolerances) are carefully matched to provide the desired tight fit.

In high-speed production, however, such alternatives can be prohibitively costly. In such cases, manufacturers have benefitted from substituting beveled retaining rings, which offer unique spring characteristics. The 15-degree bevel on the grooved side of the ring acts as a wedge between the grooved wall DESIGN WORLD

and the retained part, which then locks securely. This is unlike the bowed ring, which may deflect while under the load.

Although bowed rings offer greater endplay take-up than beveled retainers, beveled rings offer rigid endplay takeup and should be considered where cyclic loads occur. An additional consideration: high rotational speeds do not work well with beveled circlips.

Applications without grooves Self-locking rings are used on shafts or within bores without grooves and have a flat rim that supports moderate static loads.

Its prongs or teeth resist any counterpressure by digging lightly into the shaft.

These single-use rings can only be installed in one direction and are destroyed upon removal. An external grip ring can move in either direction and its position can be adjusted after installation. This style is more suitable for applications where components may have to be disassembled for repair or maintenance.

Whatever the requirement, there is a retaining ring to meet it. When choosing the ideal component, consider the application’s requirements, including its force or load, the frequency with which the rings will be installed or removed, and the installation method.

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Rosa E Hearn CFS, Product Manager — Proferred Rivets Brighton-Best International

rivets

What are the typical riveting faults and how can they be avoided?

To select the correct length for a rivet, measure from the underside of the head to the tip of the stem. The head itself is not included in this measurement.

“These rivets are faulty” or “These rivets don’t seem to work with this rivet gun” are phrases you might have heard (or said before) if working in the construction or fastener industry. Even the best of the best rivet distributors must deal with inexperienced end-users, buyers, and newbies.

Product knowledge and experience are invaluable. If you’ve never affixed a rivet, ask your fastener supplier to show you how to pull a rivet and hold a rivet gun. With strong product knowledge, you’re better equipped to safely and effectively get the job done — or teach others how to get the job done!

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First…the basics A rivet is a permanent, non-threaded mechanical fastener typically made of steel or aluminum. It has a head on one end and a cylindrical stem (the “mandrel”) on the other, which looks like a metal pin. The mandrel deforms during installation, expanding to securely hold the rivet in place.

Riveting is ideal for the quick, costeffective yet durable fastening of plastic or metal and, particularly, when the assembly remains permanently affixed or if access is limited.

The type of rivet and tool used depends on the application, and there are several choices available.

As one example, blind rivets use a clamping force and are ideal for use

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when only one side of an assembly is accessible (making them “blind” to the opposite side). They’re mostly tubular with a mandrel through the center.

When inserted into drilled holes, a tool is used to draw the mandrel through the body of the rivet, which expands and deforms the back of the body. The mandrel then snaps off, leaving a clean, finished-looking application.

On the other hand, solid rivets are one of the oldest, most commonly used fasteners and require access to both sides of an application for installation. They’re ideal for important structural joints and are often used in several critical industries. During the installation process, the rivet flattens against the back of the hold so DESIGN WORLD

that it can never unscrew. However, these fasteners can be removed or uninstalled with a drill.

These are only two options. There are several types of rivets with different features — such as those that are waterproof and sealed or split (which are ideal for wood assemblies). There are also rivet nuts that are threaded and add strength to an application.

Additionally, there are several types of rivet guns for installations, including: • Hand riveters are a manually operated tool used to install blind rivets. They have a simple lever and use a squeeze technique to work.

• Pneumatic rivet guns are powered by compressed air, with a built-in catch, to quickly install blind rivets. These tools require a hosed, compressedair connection.

• Battery-powered rivet guns offer more maneuverability and versatility, since there’s no cord, and work with the push of a button. There are two main tool types: the first one pulls mandrels into a mandrel holder so a user only has to empty the catch; the second one spits out the mandrels from the front of the tool.

Calipers are a good way to determine your proper grip range to avoid grip thickness — whether over the maximum or under the minimum.

Within those options, there are choices related to ergonomics, power rating, and battery life. Ultimately, the ideal choice comes down to the assembly requirements. This should include an assessment of the clearance to determine if the tool will fit a given space to be used correctly.

It’s important to ensure your rivet tool is perpendicular to avoid improper alignment and to minimize the occurrence of unsuitable hole conditions.

Common riveting failures Typically, the rivets or tools are not to blame for riveting failures. In most cases, the operator holds the tool incorrectly when drilling the hole — and often perpendicularly, creating an oversized or irregular hole. As a result, a blind rivet will not perform properly.

If the mandrel breaks off above the rivet face, leaving a portion that sticks out of the rivet, this is called a high mandrel break.

There is more than one potential root cause, including that the: • Assembly material for riveting is too thin or soft • Grip thickness is below the minimum recommended amount • Hole diameter is over or under-sized • Hole conditions are improper and not ideal, such as if there’s an: o Excessive variation in size o Improper alignment of the tooling for an application If the mandrel head of the rivet pops out, this is called a pull-thru or partial pull-thru.

The cause could be because the: • Body length is too short • Grip range is above the maximum recommendation • Hole diameter is oversized or above the maximum recommended size • Assembly or hole conditions are not ideal. Examples include: o An excessive variation in hole size o A non-circular or a tapered hole o Burrs or sharp edges (can occur when drilling and should be removed before riveting)

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rivets o The assembly material for riveting is too soft or there’s a gap between the material thickness o Improper alignment of tooling to application and the use of a nonperpendicular set o The wrong nosepiece used for tooling Some other potential riveting challenges or failures are less common but can occur, including if: • A rivet’s head unexpectedly pops off (the “head popper” problem) • A tool experiences a loose set • The rivet length is insufficient, not allowing for the proper formation of a secondary head at the back of the application (the “sheared” secondary head)

Depending on the problem, you’ll want to check for if the: • Grip thickness is above the maximum or below the minimum recommended amounts • Hole diameter is below the minimum recommended size • Assembly or hole conditions are not ideal. Examples include: o An excessive variation in hole size o A non-circular or a tapered hole o Burrs or sharp edges (can occur when drilling and should be removed before riveting) o The assembly material for riveting is too soft or there’s a gap between the material thickness o Improper alignment of tooling to application and the use of a nonperpendicular set

o The wrong nosepiece used for tooling o An insufficient secondary side clearance A rivet supplier should be able to help you determine the cause of any installation problems and suggest the ideal rivets and tools for use, depending on the application. It’s important to work with a company that has experience and genuine confidence in its product lines.

If you’re a supplier, when you focus on selling solutions instead of products, your customer interactions will be much more successful.

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Pam Berry

SCREWS: Duplex screws

Owner | VP of Marketing Advance Components

What is the difference between Duplex Nails and Screws?

Studies show that Duplex Screws can be installed as fast as 45 screws per minute compared to Duplex Nails at 24 per minute.

Duplex Nails and Screws are flangedhead or double-headed fasteners that are often used to build temporary structures such as braces, scaffolding, and concrete formwork. They’re designed to be removed with ease, so they do not completely go into the wood during installation.

First came the nail Duplex Nails are as strong as regular nails, but the double head makes them easier to remove with a claw hammer or crowbar.

Workers drive the nail until the lower flange is flush with the material. With a pull bar or the reverse end of a claw hammer, the nails pull out after the job is complete.

Depending on the application, if a lot of force or bending is necessary to remove the nails, they might not be reusable.

William Arthur Collings of Missouri received a patent for the Duplex Nail in 1917. His description detailed how the double-headed nail was ideal for use on concrete forms because it was easy to remove compared to regular nails, without damaging the forms.

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Duplex Screws outperformed Duplex Nails in timed comparison studies.

Collings wrote: “After the concrete has set sufficiently, the forms are removed, but due to the fact that the heads of the nails are driven into the wood, it’s extremely difficult to remove the nails without damage being done to the forms, which frequently have to be broken and even smashed to pieces in their removal, thus causing a considerable waste of material and loss of time.”

Today, there are several available styles and sizes of Duplex Nails, which are made by manufacturers worldwide.

Then came the screw Duplex Screws feature a double-hex head, which accepts a variety of driving tools — including a pile driver or hexhead screwdriver — for installation and removal after use. The driver drills the orange hex-head screw until the stop flange is flush with the material, and can easily remove it by reversing the drill.

Since there’s no need to force the removal, the screw maintains its shape and can be reused multiple times Duplex Screws were patented in 2007

by Daniel Carrillo Sr. and Hector Carrillo of California, and the patent was assigned to Removerite Inc. in 2013. In their application, the Carrillos said that the Duplex Screw is ideal for concrete formwork and better than double-headed nails.

The Carrillos wrote: “Removal of the double-headed nail from poured concrete has proven difficult. When removing the forms with a hammer or pry bar, substantial pressure is placed on the forms, which can break the edge of the freshly poured cement.”

Timed tests In timed comparison studies, Duplex Screws outperformed Duplex Nails by a

Duplex Screws and Nails are ideal fasteners for temporary structures that must be erected quickly and removed with little effort.

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wide margin. During three workdays, a pair of concrete-form setters built a 50 x 50 lineal-foot form. One worker used only Duplex Nails and the other worker used Duplex Screws. The Duplex Screw user outperformed the Duplex Nail driver in setting and form stripping, completing the task in six compared to eight hours.

In another study, crews were timed for one minute to see how many screws and nails could be installed in the same amount of time. The results showed a 47% difference, with 45 Duplex Screws drilled in versus 24 Duplex Nails hammered in.

Job safety Safety on the job site is always a big consideration. Hammers are notorious for causing hand injuries and are among the top four causes of injury in the construction industry. Most injuries involve broken or badly bruised thumbs and fingers. Although some power drills can be quite heavy, they’re generally easier to use www.fastenerengineering.com

and mishaps or injuries are rare.

According to recent reports from the National Safety Council and the Bureau of Labor Statistics, the average hand injury claim can cost from $540 to $26,000 per patient. Lost-time workers’ compensation claims for hand injuries can exceed $7,500. A badly broken finger or thumb can result in more than a month off work and can leave lasting disabilities.

To hammer or drill?

It all comes down to convenience, cost, and performance. Duplex Nails are readily available in a multitude of styles and sizes and are sold everywhere. Duplex Screws are only available from select distributors, come in sizes 1-1/4, 1-5/8, 1-3/4, and 2-3/4 inches. They cost more than Duplex Nails.

However, Duplex Screws outperform Duplex Nails and are reusable. All of these factors that must be weighed when deciding on what fastener is the right one for the job.

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Kim Keating

SCREWS: security screws

Director of Customer Success ZAGO Manufacturing Co.

Security or tamper-proof seal screws — such as the six-lobe flat head seal screw (left) and the sixlobe button head seal screw (right) — prevent unauthorized removal, thanks to a pin in the center of each drive. A rubber O-ring also forms a 360-degree, leak-proof seal.

What are tamper-proof seal screws and when should you use them?

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Security or tamper-proof seal screws are vital for securing indoor and outdoor, high-asset machinery and the sophisticated components within them, such as 3D cameras and sensors.

These specialty seal screws prevent contaminants from leaking in or out of equipment. They also contain a locking mechanism that will not break or open without proper tooling, effectively deterring vandalism and tampering.

After the screw is torqued, the O-ring is sealed and will not break or crack. This ensures the fastener is impervious to contaminants that may seep into and damage equipment or leak out into the environment, including:

The seal difference While security or tamper-proof seal screws may resemble standard security screws — and are all inordinately difficult to remove — there is one significant and visible difference. Security seal screws feature a custom groove under the head of the screw and are engineered with a 360-degree rubber O-ring that, when tightened, squeezes outwardly to form a 360-degree hermetic seal.

Security seal screws are designed for indoor and outdoor use and can withstand harsh weather, high atmospheric pressure, and extreme temperatures (hot and cold). They’re also vibration and corrosion-resistant, and pollutant-free.

These screws often provide a more convenient alternative to permanently fastening or welding parts together. This is because

December 2021 www.fastenerengineering.com

• Liquids • Moisture • Precipitation • Saltwater

• Oil • Gas • Disinfectants • Dust or dirt

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critical equipment often requires fastening, with the option to open or disassemble at a later date for maintenance.

Applications Increasingly, security and tamperproof seal screws are used to protect automated machinery from wear and tear or malfunction. They can also protect the fragile sensors that capture, store, and transmit sensitive data from physical disruption or cyberattacks.

These fasteners are often used when LiDAR (or Light Detection and Ranging, which is a remote-sensing method that uses light to measure variable distances) is employed, including for autonomous vehicles, robots and co-bots, and drones whether aerial, ground, or underwater.

A few of the industries and equipment applications that rely on security seal screws to protect hardware and components from tampering and contamination are:

• Advanced manufacturing (3D printers) • Electronics and enclosures • Energy generation and utilities • Marine (3D cameras) • Medical devices • Military and aerospace • Telecommunications • Transportation What’s ideal for certain applications is that security or tamper-proof seal screws can be removed and reused multiple times for maintenance purposes (with the rubber O-ring intact). However, they will not unscrew without the proper tooling to remove the pin.

Adding this feature prevents unauthorized users, including customers, from removing screws and attempting maintenance that should only be performed by skilled or trained personnel — such as with portable medical devices (including heart monitors or dialysis machines) or automotive software.

Materials Security and tamper-proof seal screws come in six-lobe pin, socket pin, spanner, as well as one-way slotted and corrosion-resistant metals, such as stainless steel and steel alloys.

A variety of rubber O-rings are also available, and the ideal choice depends on the equipment application and environmental exposure (such as moisture or heat). Options include silicone, fluorosilicone (a variation of silicone rubber that maintains high temperature), Buna (Nitrile rubber), Viton, neoprene, and others.

Security or tamper-proof seal screws with rubber O-ring technology protect automated machinery, such as robots and co-bots, from contaminants, as well as sensitive electronic components from tampering.

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Caia Baker VP of Procurement Fasteners Direct

s u p p ly c h a i n

How to ensure a successful fastener supply chain?

Post-pandemic wholesalers are maintaining stock in efforts to prevent any unforeseen delays. This warehouse has added its most frequented items to ensure no stockouts.

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Whether it’s a buyer of copious quantities of fasteners for ongoing projects or a onetime consumer assembling a work-fromhome desk, it’s important to recognize the value of a buyer and supplier interaction within the supply chain. Treating this exchange as a relationship — and a potential long-term partnership — rather than a transaction is one key to long-term success for both parties.

The global pandemic emphasized the significance of supply-chain partners for several in the fastener industry. Frantic purchases, frequented stockouts, shipping delays, and skeletal workforces highlighted how prepared (or ill-prepared) many companies were to handle the sudden changes and restrictions.

However, it has been said that challenges bring opportunities. If 2020 offered nothing else, it forced companies to re-evaluate their systems for doing business to identify faults and ensure resilience. For

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many, perseverance was the only option, which meant generating and adopting new ways of conducting business.

This required flexibility and modifications, such as investments in a more secure online presence and remote accessibility for customers and employees.

For example, collaborative platforms such as Microsoft Teams, Dropbox, or Smartsheet let users transmit data in real-time with the ability to connect, do business, and track orders digitally. For essential-service manufacturers and suppliers, it also meant re-distributing the workforce for a period of time to meet distancing regulations in an effort to fulfill customer demands.

The changes and challenges over the last couple of years also likely strengthened many supplier-buyer relationships. It quickly became evident which companies could meet the challenges and remain dependable.

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Knowledge is power. There are many options in the fastener industry.

Consumers may be unaware of their choices when it comes to new or full product line capabilities. Suggesting options or providing professional installation tips adds quality incentives.

A specialized customer-service team who can share insightful product and assembly knowledge is highly attractive.

Material test reports and certificates of compliance are also wise additions to provide consumers with product sourcing knowledge.

Inventory management is a critical link in any supply chain.

Ensure you continually track what products you have in stock, what’s typically required (and when), the costs, and delivery times to ensure you’re optimizing your revenue and supply-chain relationships.

Despite the disruptions from the pandemic, however, some things never change when it comes to good business relationships. Whether you’re a manufacturer, supplier, or buyer in the industry, here are some tips to ensure a good relationship with your customers.

It starts with communication. A wise person once said, “communication is key.” Within the supply chain, communication is imperative. This is no time for modesty or timidity. Be clear about what you want and truthful about you can offer or budget for.

Moreover, prioritize those stakeholder relationships and keep in contact regularly.

If you’re a manufacturer or supplier, keep customers appraised of your products and offerings. Offer options and good service.

Beyond mass emails or e-newsletters, it’s worth reaching out to customers personally to maintain a strong bond.

If you’re a buyer, form a good relationship with your suppliers, so they clearly understand your needs and can then consistently meet them.

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Expect competition. The emergence of Amazon Prime has added a new level of competition for certain manufacturers and suppliers. Often suppliers will offer unique components or smaller quantities on third-party sites, such as Amazon.

With e-commerce becoming more popular, particularly since the pandemic, it’s worth surveying the online presence of potential vendor(s) as the heavy-hitters will take advantage of several platforms.

A stronger online presence might also be something that could serve your company.

Know your customers — and your potential new customers.

Exceed expectations.

There are basic factors that consumers require from suppliers. And ironically, it’s not simply better pricing, even though this is typically one component. When suppliers meet or exceed consumers’ expectations, it’s considered a win-win for all parties involved.

If expectations are unmet, this typically means the stage has not been properly set and better communication (or listening skills) is required. A good rule-ofthumb: under-promise and over-deliver.

Stick to a code. In the fastener industry, standards are critically important to ensure safe assemblies. A code of ethics should also be followed in supply-chain www.fastenerengineering.com

relationships. Trust goes a long way in securing good partnerships. Be honest, keep your word, and be kind.

One best practice is to seek a non-compete supplier. A noncompete agreement offers assurance that vendors will not sell to or provide a service to the client’s direct competitors or disclose trusted insight or private information.

As a buyer, don’t be shy about a manufacturer or supplier’s values and standards. Ensure what you’re paying for also offers peace of mind, security, and confidence.

Go with the flow. The supply chain is continuously evolving. If nothing else, you can expect challenges and changes over time, which are an important part of development. Flexibility is important.

Remember, it’s always possible to grow and there are several strategies to improve the bottom line. Don’t be shy when it comes to advancing business practices, trying new digital platforms, or reaching out to new customers.

Identifying supplier relationships that align with your business goals can lead to increased efficiencies and reduce the costs associated with establishing new partnerships.

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training: courses

Why is fastener training important?

The Fastener Training Institute is once again offering in-person classes throughout the U.S. and has live, monthly online webinars. Review their 2022 classes at fastenertraining.org.

The significance of choosing the right assembly method might not become obvious until an application fails, and the fasteners are to blame. Granted, it’s one thing if a few books fall off of loose shelving. But when it’s a vehicle with loose tire lug nuts or a pressurized bolted flange joint assembly that begins to leak, the outcome might result in a major safety hazard.

Fasteners and bolted joints are critical to the safe operation of many types of equipment in applications including power generation, manufacturing, mining, and transportation. However, fasteners are typically one of the lowest cost items in any structure and are often the most neglected or last considered.

This is, perhaps, one reason fastener training is of low priority in most design and engineering programs. In some ways, this makes sense. Fastener manufacturing is a mature industry, and the majority of producers supply high-volume parts with single-digit defects. Only rarely are the fasteners at fault for failures.

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“The vast majority of fastener-related problems arise from improper selection, specification, misuse, or installation,” shares John Wachman, managing director of the Fastener Training Institute (FTI), a non-profit launched by experienced industry professionals to provide fastener product training and continuing education. “But regardless of the cause, a fastener or joint failure can cost lives at worst or simply be a costly inconvenience.”

When designing, manufacturing, or installing the larger assembly, it’s important to avoid overlooking the smaller, critical components that hold it together.

“Fasteners can be simple components,” says Wachman. “Their complexity relates to the vast options that design engineers have when choosing the ideal components for an assembly.”

The wrong choice can lead to shorter product lifespan, poorer performance or failures, and increased labor costs for repairs or replacements.

To ensure fastener reliability and integrity, there are several factors to consider, including the:

December 2021 www.fastenerengineering.com

• Material properties • Temperature (minimums and maximums) • Environmental conditions (humidity, moisture, gas, debris, etc.)

• Application stressors (vibration, dynamic loads, shock, etc.).

It’s advisable to choose fasteners that are made of higher quality than the parts that they will hold together. However, there are more questions to ask.

For example: How many fasteners are required for a given application — and to ensure the expected product life? What size, style, and equipment or tools are needed for proper assembly? Will the application need to be serviced and how often?

“There are many fastener options, such as the size, as well as the diameter and length, head style, drive, material, coatings, plus any quality requirements,” Wachman points out. “The fastener industry is also innovative and without current knowledge or training, a superior fastener solution might be missed.”

DESIGN WORLD

This means that to ensure the safest, most productive, and cost-effective products and applications, updated and ongoing fastener education is essential.

Training options Training that enhances the level of technical understanding and expertise of individuals in the industry is critical for a successful industry.

Look for a program that: • •

• •

Fully covers fastener products, standards, and specifications Teaches proper fastener selection and installation methods to prevent unnecessary faults and failures Is hosted by recognized industry experts with years of experience Offers hands-on training, when possible

Many fastener manufacturers will offer online or in-person training sessions for customers, as do most standards’

organizations — such as the Industrial Fasteners Institute (IFI), the American Society of Mechanical Engineers (ASME), the Occupational Safety and Health Administration (OSHA), etc. Here are a few other options...

Fastener Training Institute (FTI). FTI provides beginner and advanced training on fastener products, standards, and specifications, with full-day and weeklong classes (FTI’s Fastener Training Week is an industry mainstay).

“FTI’s core purpose is to enhance fastener use, reliability, and safety by providing fastener product and technical training at all levels,” says Wachman.

They also offer live webinars and have an extensive On-Line Training Library. FTI often partners with IFI for its training events. fastenertraining.org FastenerClass. A global manufacturer of mechanically attached fasteners,

Würth Knowing YouTube Series was inspired by the company’s Fastener Academy training. The online series dives into topics related to fastener engineering, bolted joint design, and proper assembly — covering basic to complex concepts, including a funny story or two.

Check it out at youtube.com/wurthindustrynorthamerica.

DESIGN WORLD

www.fastenerengineering.com

PennEngineering is offering an opportunity to learn from the leading experts in fastening technology via FastenerClass — and at no charge.

The customized training sessions are designed to give attendees actionable insights from industry experts who cover theory, best practices for fastener selection, application examples, and more.

Participants will also learn how to test and confirm fastening designs with support from PennEngineering’s PEMedge services, which supports exploring and testing alternative fastening solutions available to design engineers. The aim is to find innovative ways to improve cost, assembly time, strength, weight, and aesthetics. info.pemnet.com/fastener-class The HYTORC Bolting Institute (HBI).

HBI has the goal of educating all of those engaged in industrial bolting to significantly improve the safety, quality, and efficiency of bolting operations.

HBI regularly delivers technical certificate training classes for a variety of job functions — from operators and technicians to managers and engineers.

HBI also offers regularly scheduled online public short classes, which are brief, non-certificate classes. HYTORC partners with ASME and OSHA to provide standardized technical training that maximizes the educational value. hytorc.com/training The Würth Fastener Academy. This Academy is tailored specifically for its audience. Würth provides in-person training at a company’s facility, with an engineering team that offers real-world experience and insights. Attendees will learn answers to the complex questions that often come up when dealing with the broad spectrum of fasteners, as well as cost-savings methods and options.

Course objectives include torquetension, corrosion and fastener finishes, manufacturing processes, fastener materials and mechanical properties, thread inspection, standards, and more. tinyurl.com/WurthTraining December 2021

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Article courtesy of the Fastener Training Institute

training: faqs

It’s important to know your fastener facts and standards to ensure a high level of safety and accuracy when assembling structural buildings or applications.

What are some critical structural fastener facts you should know?

The late Joe Greenslade, an icon in the fastener industry, once wrote: “The technology of mechanical fasteners is much more complex and varied than most people understand until they embark on a career where they either supply or specify the use of mechanical fasteners.”

Those with a career in the industry can most certainly attest to the accuracy of this statement. Those who are in the process of training or upgrading their skills can also likely relate to the importance of learning about the different fastener types, materials, tools, and assembly methods available.

After all, these components are responsible for holding or joining

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applications together. It’s extremely important to specify and choose fasteners wisely and install them correctly.

Greenslade taught mechanical fastener technology for 45 years, publishing more than 300 informational articles. He also served eight years as the director of Engineering & Technology at the Industrial Fasteners Institute, a trade organization for North American mechanical fastener manufacturers.

In 2015, Greenslade compiled a list of his most frequently asked questions with answers that cover the specifying, inspecting, and installing of mechanical fasteners — and more.

Here are a few of his answers that

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are mostly related to structural bolts, materials, and related standards.

What are the four most commonly used structural bolt material standards and what material strength levels are they associated with?

The most commonly used structural bolt material standards are ASTM A325 and F1852, which are 120 ksi tensile strength, and A490 and F2280, which are 150 ksi tensile strength. These grades are covered in the ASTM F3125.

What is the difference between Type 1 and Type 3 structural bolts?

DESIGN WORLD

Type 1 structural fasteners are made from carbon or carbon-alloy steels and require coating and/or painting to avoid rusting. Type 3 structural fasteners are made from “weathering steel” that oxidizes to a point and stops, eliminating the need to coat or paint to avoid further rusting.

What is the dimensional standard covering inch structural bolts?

ASME B18.2.6 is the dimensional standard that covers inch structural bolts.

What are the two styles of structural bolts, and which is the most popular?

The two styles of structural bolts are Heavy Hex and Tension Control (TC). TC is the most popular structural bolt because of faster assembly and visual inspection.

What is the applicable washer standard for structural bolting?

ASTM F436 is the applicable washer standard for structural bolting.

Meeting standards is critical to ensure a safe and reliable assembly. Organizations, such as the American Society of Mechanical Engineers (ASME) and ASTM International, support the industry with the latest codes and standards for testing, materials, and engineering.

DESIGN WORLD

What should be the relationship of an assembled bolt end be to the top surface of a nut in structural bolting?

An assembled bolt end should be at least flush to the top surface of a nut in structural bolting.

The rotational capacity (ROCAP) test: how is it performed and what is its primary purpose?

A “ROCAP” test is performed using exact bolts, nuts, and washers tightened in a Skidmore (hydraulic) tester, tightening the nut to 10% of the target bolt tension. Then, rotate the nut the number of degrees designated in the ASTM F3125 standard.

The bolts must not break and once the nut is broken loose, the nut must unscrew by hand.

The primary purpose of a ROCAP test is to determine if adequate nut lubrication is present to enable proper fastener tightening without failure.

According to ASTM F3125 (Table 3, Note A), the ROCAP testing of galvanized assemblies is mandatory. Testing may be required by the purchaser by specifying “Supplementary Requirement S.4” at the time of inquiry and order for plain or assemblies having other coatings.

The test must be conducted using the exact lots of bolts, nuts, and washers, if any, that will be used on a job site.

Why should all of the exact fastening components be shipped to the job site by the same supplier?

According to the RCSC standard, when performing a ROCAP test, all of the fastening components should be shipped to the job site by the same supplier to assure the exact mating parts will work on the job site.

The late Joe Greenslade, who was an industry expert in the fastener sector.

washers on the job site will assemble properly when constructing the structure prior to actual assembly starting. It must be performed and documented by the assembly crew doing the installation.

What is the specification that governs structural steel assembly?

Research Council on Structural Connections (RCSC) is the specification that governs structural steel assembly.

What are the three things that can be tried to stop the galling of stainless bolt and nut threads?

Three things that can be tried to stop the galling of stainless bolts and nuts are using a different grade of stainless for the mating components, slowing down the installation RPMs, and lubricating the bolt and/or nut with thread lubricant.

To read additional FAQs from Greenslade, go to https://tinyurl.com/ FastenerFacts.

What is a pre-installation test and why is it required?

A “pre-installation test” is a test performed on a job site using the exact components and assembly technique specified for the structure.

The pre-installation test is required to demonstrate that the bolts, nuts, and www.fastenerengineering.com

December 2021

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Deanna Postlethwaite, Sr. Director Program Management STANLEY Industrial

TOOLS

Reducing downtime is one key to a successful preventive maintenance program for tool and equipment use. Ensure the correct tools are in place, plan ahead for replacement parts, and always ensure workers are properly trained.

What are the best practices for tool and equipment preventive maintenance?

Reducing or eliminating the risk of unplanned downtime, manufacturing interruptions, and missing repair stock is an issue every manufacturer addresses at some point. One effective way to achieve best practices is to work on implementing a service preventive maintenance (PM) program to maximize manufacturing time and extend product quality and machine life.

Gaining a commitment within one’s organization to set up a regular

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PM program is the first step but implementing preventive maintenance in a way that’s flexible and manageable is critical to ensure that downtime and interruption risks are avoided. It’s not just saying it, it’s doing it.

What are the key drivers for success?

A manufacturer can begin the PM journey by defining what they want to achieve, such as:

December 2021 www.fastenerengineering.com

• Extended tool and equipment lifecycles by eliminating breakdowns or failures • Increased tool and equipment product quality • Decreased high-dollar expediting fees and spare-part costs by planning out PM schedules • Decreased cost of additional workforce required to run or verify backup processes DESIGN WORLD

To create a comprehensive plan: Gather tool and equipment manufacturer (OEM) information on the tools and equipment Evaluate, with the OEM, the usage and PM guidelines from the factory — based on your application usage, create a baseline plan for preventive maintenance and repair Plan a PM program (some areas of the plant may be different based on applications and use of the tools and equipment) Ensure the proper supplies and spare parts are on hand and a re-order plan is in place once the parts are consumed to ensure the necessary inventory is always on hand Establish checklists for each area Audit the plan and implement changes based on successes or failures Who drives success?

The ideal leader for any given PM program is the maintenance team. Along with possessing the correct skills, they’re experienced practitioners of the product workflow and are responsible for the high-quality output.

support, and knowledge can help develop the correct processes and habits from the start to support the team — and to keep the program active.

Once the assessment of and planning for the program are complete, the PM implementation team will depend on the size and complexity of the facility.

Typically, this team is relatively small.

The focus should be on the rollout, acceptance, and results of the program with the extended teams.

How can success be measured?

When the program is implemented, success can be measured and celebrated with the team involved after any ongoing challenges or problems are resolved.

Depending on the tools, equipment, and the type of application, some of the performance indicators to measure success are:

THE IDEAL LEADER FOR ANY GIVEN PM PROGRAM IS THE MAINTENANCE TEAM.

A successful maintenance program means decreasing the likelihood of tool or equipment breakdowns and failures. Invest in quality products and follow the manufacturer’s guidelines for use and care.

In addition: • Engage the service and repair teams (internal and/or external) in the planning and ask for feedback • Involve the quality team to implement the process as part of the standard operating procedure • Lean on OEMs and/or your distribution partners who can provide sales and servicing support • Manufacturing and operations teams must buy-in and commit to the plan to rotate tools and equipment for preventive maintenance to ensure a quality PM program The lack of expertise and acceptance from the team is the primary reason PM programs may fail.

Accessing the proper assistance,

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www.fastenerengineering.com

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TOOLS • Improved system uptime • Reduced system lifecycle costs • Planned maintenance percentage – the time spent on planned versus unplanned maintenance • Preventive maintenance compliance rate – how many scheduled PM work orders are completed within a set amount of time • Critical scheduled maintenance percentage – the impact of late planned maintenance work • Downtime analysis for root cause and resolution timing – downtime resolution and timing

maintenance and repairs, and supporting the team with the necessary information to excel. The team can and should identify this when the goals of the program are created and evaluated.

With any program, there are opportunities to enhance and supplement the program with digital tools to assist in collecting data, tracking

Implementing a PM program will:

Summary There are several reasons why it’s important to implement a preventive maintenance program and, over time, the program will pay for itself.

Avoid waiting for the high cost of downtime and failure, or losing on investments, before implementing such a strategy.

• Reduce the chances of complete breakdowns • Recognize the problems earlier through a preventive maintenance plan • Reduce the chance of emergency repair calls and overtime to resolve issues • Reduce downtime for bringing in and expediting spare parts • Reduce the potential of unnecessary repairs

• Ensure continued uptime, while reducing downtime

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DESIGN WORLD

800-WASHERS

Article courtesy of NBK

WASHERS

Washers are available in a variety of types, sizes, and materials. Steel and stainless steel are the most common, but other metals and plastics are also used, depending on the application. Regardless of the washer chosen, installing with the proper torque is the best way to ensure a reliable hold.

How do flat and lock washers differ?

Generally, washers are used to distribute a fastener’s load, reducing friction and preventing loosening. A washer is a plate with a hole, which lets a fastener pass through it. The most common shape is a flat disk with a concentric hole.

Before a threaded fastener, such as a bolt, is driven into an application’s surface, a washer is often placed through the end for greater protection during installation and over time. This is because threaded fasteners stress the material in which they’re used.

During installation, the washer works

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by absorbing the compression forces of the bolt as it’s driven into the application.

A washer is positioned at the top of the bolt’s shaft where it meets the head and slides into the mounting hole, preventing the bolt head and nut from scratching or indenting the surfaces of the two fastened parts.

Otherwise, without the washer, this could damage the application’s surface and eventually loosen the fastener. So, washers often offer greater reliability.

There are several types of washers available and, as with any fastener,

December 2021 www.fastenerengineering.com

choosing the ideal one depends on the application. For example, they might be sprung to prevent vibration and loosening or to indicate the correct preload. They might be serrated or tabbed to prevent unscrewing.

Regardless of which washer is chosen, tightening with the proper torque is the best way to ensure a reliable hold.

By far, the most common is the flat (or plain) washer. Its purpose is to distribute a fastener’s load while reducing heat and friction during the installation process.

DESIGN WORLD

Since flat washers are generally manufactured by pressing metal, one side has rounded corners and one side has burrs. There’s no fixed rule about which side should be placed up or down but placing the burred side facing down is typically ideal, particularly if surface pressure is a concern.

Bear in mind that these burrs can also mark the surface of the fastened object during tightening so, for certain applications, it may be better to put the rounded side down to avoid plate peeling. It’s also worth noting that flat washers are sometimes used as spacers, which is common in industrial and domestic applications.

Lock washers are also quite common and designed to secure fasteners that might otherwise rotate or lose friction, such as in high-vibration applications. In other words, these washers are solely designed to “lock,” keeping nuts and bolts from coming loose. There are several types of lock washers and each is designed for use with a particular fastener or application.

For example, spring washers are a type of lock washer made by cutting out part of a flat washer so that it can form a twisted shape. This results in a spring action or an elastic force. Unlike flat washers, which are placed on both the bolt and nut sides, spring washers only go on the nut side of the fastener to establish a bond. Essentially, the cut part “bites” into the bearing’s surface.

This locking effect due to “biting” is limited to applications in which the material of the fastened object is softer than the metal washer. Spring washers have proven useful for anti-loosening, especially in the semiconductor sector due to the heat cycles and the material’s thermal expansion coefficient.

External-tooth lock washers, also known as “star” washers, have teeth located on the outside of the washer ring, which are designed to offer a stronger hold and tend to be used with larger fastener heads. Star washers increase the locking force by resisting

DESIGN WORLD

the torque applied by the nut, preventing it from unscrewing or separating.

Regardless of the type, lock washers are designed for the same purpose: to exert a load, partially deform, and lock a fastener in place.

However, the sharp hold from lock washers can leave the application’s surface scratched, which is not ideal for repeated installation or removal.

For this reason, in some applications, lock washers (mainly, spring washers) are deployed along with a flat washer to distribute the load more evenly without deforming the assembly that the fastener is secured to.

There’s also an alternative to conventional lock washers. Eccentric lock washers can be combined with commercially available hex nuts to prevent screw loosening. They consist of a bearing washer and an eccentric washer. When the eccentric washer is wedged into a bolt, the bearing washer changes the commercially available hex nut into an anti-loosening nut. The added bonus is that no tools are required for installation.

Overall, washers benefit threaded fasteners in many applications. Washers protect the surface from damage during installation, evenly distribute pressure, and prevent the fastener from moving or corroding. www.fastenerengineering.com

Captive spring washers are installed under the head of a screw to ensure locking and prevent falling out. They’re ideal for semiconductor and foodrelated applications.

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welding: joints

Welding pre-heat is commonly used before welding steel or steel alloy materials that are one-inch thick or more. Typically, thicker components require pre-heat, but it depends on the materials and assembly goals.

When do joints need to be pre-heated before welding?

Welding is a fabrication process that joins materials — typically metals or thermoplastics — by using high heat to melt the parts together and then allowing them to cool to cause fusion. Welding is distinct from lowertemperature, metal-joining techniques such as brazing and soldering, which do not melt the base metal.

Pre-heating components before welding can reduce the rate of cooling and result in stronger and more reliable welds. The process can involve heating the area around the weld joint or the entire part to a specified temperature before welding.

When thicker components are preheated, it’s typically possible to achieve

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December 2021

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an ideal bond with less heat during the welding process. Thicker material means that more of it, including the surrounding material, will act as a heat sink when welded. This leads the weld to cool more rapidly after the energy source is removed.

Although thicker components (usually one inch or thicker) are more likely to require or benefit from preheating, there are several criteria to consider beforehand.

To accurately assess if a welding assembly requires pre-heat first consider the type and thickness of the base material. Although it’s difficult to provide simple rules for the material thickness at which pre-heating is ideal, there are rules-of-thumb and different DESIGN WORLD

considerations for different materials.

For example, with alloys, the tensile and yield strength are significant considerations. Tensile strength refers to the breaking point of an alloy and yield strength is the point at which stress or pressure causes an alloy to deform.

Typically, pre-heating is based on the welding code that’s used for the project. Welding codes are developed and available from several organizations and set the requirements for approved materials, design specifications, testing, inspection, as well as the welding itself.

The most commonly used codes are from the American Society of Mechanical Engineers (ASME | Section IX) and the American Welding Society (AWS | D1.1).

DESIGN WORLD

The advantages The rapid heating and cooling of the base metal during routine welding can put heavy stresses into the parts, creating hard structures that are susceptible to hydrogen embrittlement.

Hydrogen embrittlement is a permanent loss of ductility in a metal or alloy caused by hydrogen in combination with stress. Pre-heating reduces the cooling rate of the weld and drives out moisture. A slower cooling process provides more time for hydrogen to defuse from the weld-affected zone, which reduces the risk of cracking.

Additionally, slower cooling produces microstructures in the weld metal and the heat-affected zone, which are more ductile and provide a greater resistance to cracking. Shrinkage stresses are also less likely to occur.

Residual hydrogen can become trapped at different sites within the metal, so the technique and weld temperature are important considerations that might require adjusting. Depending on the metals, welding with a longer contact-tip-towork distance can remove hydrogen from the weld area. A longer electrical tip can create greater preheating of the wire, burning off more hydrogen before the parts weld.

However, it’s critical to follow the recommended ranges for the material to be bonded. Careful monitoring of the base metal’s temperature between weld passes is important to ensure the material remains within the required range, regardless of the technique used.

Joint preparation is also critical because dirt, rust, debris, coatings, or oils can introduce hydrogen into the weld. Ensure the joint is clean and completely dry before welding.

Welding with restraint can generate additional residual stresses in the weld, which may cause cracking. With each assembly, be mindful of how the parts for joining are positioned and how the material reacts to welding. www.fastenerengineering.com

When an ideal option, pre-heating can be achieved using different heat sources. For smaller components, a furnace or oven can be used, and this may provide the best process control.

For larger components, options include: • • • •

Arrays of torches Electrical resistance heaters Induction heaters Radiation heaters

Process control is extremely important when pre-heating, to ensure the material is heated to the correct temperature and that it remains within the required temperature tolerance throughout the welding process.

This involves three key process parameters: 1. Pre-heat temperature: the temperature of the surfaces to be joined before welding begins 2. Maximum interpass temperature: the maximum temperature at which subsequent weld runs are deposited, affecting the microstructural development 3. Minimum interpass temperature: the minimum temperature at which subsequent weld runs are deposited, affecting hydrogen cracking — typically, this is similar to the pre-heat temperature The minimum interpass temperature might need to be maintained for a specified period of time after the weld is deposited to ensure sufficient hydrogen diffusion. The temperatures can be monitored using temperature-indicating crayons, thermocouples, or contact thermometers.

Several welding pre-heating methods are available, so it’s important to understand the differences and pros and cons of each in relation to your project. The aim should be to choose a method that optimizes efficiency and costs while producing high-quality welds in your application.

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Tarick Walton Global Product Manager Ultrasonics, Branson Welding and Assembly at Emerson

welding: materials

What advances in welding address material variations?

Conventional ultrasonic welding technology, using single-parameter weld modes, has enabled electronics manufacturers to achieve high levels of assembly quality and reliability. This is particularly true for products built from rigid, molded plastic components.

Ultrasonic welding creates a highfrequency, heat-generating motion between the components to be bonded.

It’s been used to join thermoplastics for more than 70 years and has frequently been chosen when parts were too complex or costly to be molded in one piece. Instead, they were molded in multiple parts, which allowed for more efficient and cost-effective welding.

This type of welding uses single, weld-parameter modes such as downforce, distance/collapse, depth, time, or energy to manage weld consistency and high repeatability.

However, controlling weld quality with single-parameter modes becomes more challenging when assembling plastic parts that are: • Compressible or contain compressible elements • Inserted into substrates that vary in hardness • Installed over or contain sensitive metal or electronic components To assemble hard-to-handle or variable parts, manufacturers have typically had to add an external measuring device to the welder, which allows for the adaptation of a critical weld parameter.

This practice adds time, complexity, and cost to the process.

Manufacturers facing nextgeneration product assembly challenges

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— from miniaturization to increased electronic contents — require a new range of assembly innovations.

Fortunately, advanced technology is offering just that and eliminating the need for external measuring devices. This new, “dynamic mode” for ultrasonic welding

can automatically adjust to respond to part-to-part variabilities and unique materials while avoiding the need to add external measurement or sensing devices.

This technique can safely weld small, thin, or complex plastic parts onto plastic structures directly atop sensors or delicate electronics without damage. It can also weld parts atop plastic assemblies containing compressible internal elements, such as elastomeric seals or cores.

As next-generation electronic devices become smaller and lighter, ultrasonic techniques are evolving to create repeatable welds atop delicate components.

Working in dynamic mode The dynamic welding mode can monitor,

December 2021 www.fastenerengineering.com

DESIGN WORLD

welding: materials recalculate, and adjust multiple weld parameters in real-time to optimize weld performance within a user-specified target result. This provides users greater versatility and more consistent results by welding in accordance with a design profile instead of a single parameter.

To do so, users must first select the single-parameter weld mode that offers the ideal application results, and then enter two application-specific scores. These act as limits for the dynamic mode activity.

The first score is a material density score that characterizes the hardness or resistance of the material that’s to receive the welded, staked, or inserted part. The second is a weld reactivity score, which impacts the reaction time to achieve the desired density setting.

The dynamic mode then monitors each weld cycle and optimizes it in response to specific, part-to-part variabilities throughout the production run.

Here are two examples of how the dynamic mode weld cycle can overcome the limitations of single-parameter weldmode controls.

1. Sealing a watertight cover over electronics. In this example, a plastic cover must bond gap-free, watertight, and without the cover structure contacting or compressing the sensitive electronics inside the lower component.

A single-parameter weld mode (the weld distance or collapse depth) could exert too much pressure on the cover and damage internal device electronics.

By using a dynamic welding mode instead, a manufacturer can optimize the distance/collapse depth mode in each cycle and enable the weld actuator to produce enough collapse depth for a watertight seal. At the same time, this mode detects and avoids a higher resistance that could compress the cover and damage the electronics below the welded cover.

2. Welding a sealed, elastomer-core pin connector. The challenge is to assemble an elastomer-filled, two-way pin connector so that the connecting pins

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December 2021

Before view: Staking application with different number of metal washers (single and double).

are embedded in a compressible core of elastomeric plastic. The finished plugs must be air and watertight, so the weldedon lid compresses the elastomer around the inserted pins. A flat fit is essential for the lid, but the height of the plug’s elastomeric core may vary by up to 10%.

The use of a single-parameter weld mode (downforce, distance/collapse depth) risks producing unacceptable variances in the lid height, which would expose the length of connecting pins and could compromise the watertight sealing capability.

In the dynamic mode, however, the materials density score allows for a weld-by-weld adjustment, which compensates for the varied consistency and height of the plug’s elastomer core.

This mode requires that the actuator “sense” or “feel” for the specified amount of resistance (so, the contact with the harder material on the plug’s rim) before beginning the lid weld.

As advances in electronics develop, so do the assembly technologies that ensure a strong and reliable bond. Fortunately, plastic welding now offers more than one way to meet new demands. www.makepartsfast.com

After view: Single recipe setting in dynamic mode used to weld both single and double washer staking applications.

These before-and-after views show the flexibility of dynamic mode in staking a pair of metal washers onto posts. By using the Branson GSX-E1, Elite Precision+’s “dynamic mode,” a consistent weld result was obtained (see image on the right), and even though the application set-up was different and based on the number of metal washers being staked.

This is not possible using an alternative weld mode. The dynamic mode stored the material density and reactivity information, enabling it to detect the completion of the stake and dynamically shut the weld down early.

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Vendors in the fastener industry

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NBK America NBK’s historic past since 1560 has allowed it to provide new value to customers by constantly renewing itself. The NBK brand stands for strong design, precise manufacturing and sales of products based upon the needs of its customers. NBK provides high-precision, high-performance specialty screws and machinery components such as the following: Low Profile, Small Head, Vacuum Ventilation, Seizing / Galling Resistant, Specialty Metal (Inconel, Hastelloy, etc.), Miniature, Captive, Clamping, Tamper Resistant, Plastic, Loosening Resistant, Ball Roller (Transfer), Roller Chain Bolts, Spring Plungers, Knobs, and more. Furthermore, NBK has Flexible Shaft Couplings, Wireless Positioning Units, Clampers, and additional products. We can customize these products flexibly should the need arise.

NBK products are used in advanced industries, such as manufacturing equipment for automation, robotics, semiconductors, and medical devices.

NBK America LLC 307 East Church Road, Suite 7 King of Prussia, PA 19406 Web: www.nbk1560.com Phone: 484-685-7500 Fax: 484-685-7600 Email: info.us@nbk1560.com

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Pivot Point Pivot Point is a designer and manufacturer of Non-Threaded Fasteners - i.e. clevis pins, cotter pins, quick-release pins/devices, wire rope cable assemblies, and more. A family-owned company, the Leitzke family’s manufacturing heritage dates back to the 1920’s, and continues today in Pivot Point’s line of classic, and unique, fastening solutions.

Wide stock selection and endless customization options allow us to solve application challenges on tight timelines, fixed budgets, and with creative solutions. Pivot Point is known for our inventive, original, fastening solutions like our SLIC Pin™ (a quick-locking pin featuring a selfcontained cotter), Bow-Tie Locking Cotter, Rue Ring Locking Cotter, U-Lock Nylon Tether and others. Our state-of-the-art Wisconsin manufacturing facility features in-house pin design as well as automation capabilities, making Pivot Point a powerhouse in fastening solutions – at prices that can compete with imports. Pivot Point is proud to offer digital, and in-person, product training sessions. These are live, interactive sessions that cover “NonThreaded Fastener Basics.” The training is tailored to industries, teams and individuals, and schedules. Full of application examples, product comparisons, and best practices, the 1 hour (or less) session is intended to round out the knowledge of any design professional. Reach out today and let us know how we can help!

Pivot Point, Inc. PO Box 488 761 Industrial Lane Hustisford, WI 53034 Phone: (800) 222-2231 Fax: (920) 349-3253 Email: mail@pivotpins.com DESIGN WORLD

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Smalley

Founded over 100 years ago, Smalley has evolved to become the world leader in the manufacturing and development of Retaining Rings, Spirolox® Retaining Rings, Constant Section Rings, and Wave Springs. Smalley has led the way in introducing state-of-theart products and continues to lead the way in innovations for the future.

Smalley stocks over 10,000 standard parts across 30 configurations and 400 sizes. If a standard part doesn’t meet your requirements, you’ll work with our team of over 30 industry-specialized engineers to quickly create an economical custom part in the material of your choice, all without new tooling. Prototype or production volume, our No-Tooling-Charges™ manufacturing process meets the design flexibility your application, budget, and timeline requires.

While all of our manufacturing is made in our U.S.-based 300,000 ft2 facility, our global network of offices, engineers, and distribution partners allows you to receive parts and support from anywhere in the world quickly. Smalley’s dedication to quality and manufacturing excellence has earned us multiple service and quality awards and the trust of OEMs worldwide.

Smalley 555 Oakwood Road Lake Zurich, IL 60047 Phone: +1 847 719 5900 Email: info@smalley.com smalley.com

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Selecting the Optimal Washer Flat: Generally used for load disbursement Tab/Lock: Designed to effectively lock an assembly into place Finishing: Often found on consumer products Wave: For obtaining loads when the load is static or the working range is small Belleville: Delivers the highest load capacity of all the spring washers Fender: Distributes a load evenly across a large surface area Shim Stacks: Ideal for simple AND complex applications

Boker’s Inc. 3104 Snelling Avenue Minneapolis, MN 55406-1937 Phone: 612-729-9365 TOLL-FREE: 800-927-4377 (in the US & Canada)

bokers.com

Structural Adhesives For Specialty Trucks and Trailers Many truck and trailer manufacturers are making the switch to adhesives instead of traditional welding and fastening. Lowering fuel cost, wind drag, and weight has become an important component in manufacturing specialty vehicles. Several trial applications have been performed, and results have shown that the bonds of structural adhesives are stronger and more reliable. Ellsworth Adhesives offers a variety of acrylic, epoxy, and urethane structural adhesives.

Structural adhesives can be used to configure work truck equipment, trailer assembly, and aftermarket upfitting. Applications can range from panel bonding for trailers, installation of toolboxes in construction trucks, shelf hanging for delivery vehicles, plumbing equipment for firetrucks, to electrical components in utility vehicles.

DESIGN WORLD

www.fastenerengineering.com

Ellsworth Adhesives (877) 454-9224 Ellsworth.com

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J.W. Winco, Inc. Spring Loaded Devices from JW Winco When you need to align, hold, or latch different parts of equipment together, you need a spring loaded device.These locking systems are designed to facilitate repetitive positioning operations on machines and equipment or parts undergoing machining. Spring loaded devices create a secure connection with limited play. JW Winco has many different versions and types for your application requirement.

Check out www.jwwinco.com to find out more!

J.W. Winco, Inc. Phone: 800.877.8351 sales@jwwinco.com www.jwwinco.com

Keystone Electronics Corp.

A World Class Manufacturer of precision electronic components & hardware for over 70 years. Keystone’s design and engineering experts are fully integrated with their inhouse precision tool & die division supported by advanced manufacturing systems to produce close tolerance Stamping, Machining, Assembly, CNC and Injection Molded parts.

Keystone utilizes state-of-the-art software to support the thousands of standard products found in their Product Design Guide M70 and Keystone’s Dynamic Catalog on-line.

Product Overview: Battery Clips, Contacts & Holders; Fuse Clips & Holders; Terminals & Test Points; Spacers & Standoffs; Panel Hardware; Pins, Plugs, Jacks & Sockets; Multi-Purpose Hardware.

As an ISO9001:2015 certified manufacturer, Keystone’s quality control system, responsive customer service and custom manufacturing division can meet your challenges with a standard or custom design solution.

DESIGNERS & MANUFACTURERS

www.keyelco.com

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Keystone Electronics 55 S. Denton Ave. New Hyde Park, NY 11040 Tel: 1.800.221.5510 www.keyelco.com

DESIGN WORLD

Custom Plastic Machined & Molded Fastener Components ADAPTERS • BACKUP WASHERS • BOLTS • COUPLINGS • CONNECTORS • HEX BOLTS • INSULATORS • NUTS • SEALS • SET SCREWS • SHOULDER BUSHINGS • PAN HEAD SCREWS • PINS • SLEEVES • SLOTTED SET SCREWS • SPACERS • WASHERS

Materials Utilized: ABS, Acetal, Acrylic, Delrin®, HDPE, KEL-F, Phenolics (G10, G11, XXX, CE, LE), PEEK, PTFE, Polycarbonate, Polypropylene, PVC, PVDF, Torlon®, UHMW and Ultem® Please visit us at www.nextlevelmanufacturing.com

Manufacturing Solutions Since 2001 Next Level Manufacturing 401 E. Edgewater Street Portage, WI 53901 sales@nextlevelmanufacturing.com (608) 975-7424

SET SCREWS • HEX KEYS • SHOULDER BOLTS • NYLON TIP • SOCKET CAP SCREWS • STAINLESS • METRIC / INCH • ZINC PLATED SOCKETS • SHORT ARM HEX KEYS • 6-LOBE SOCKETS • BUTTON HEAD CAP SCREW • DOWEL PINS • IMPORT / USA • BRASS TIP • STANDARDS / SEMI-STANDARDS • SQUARE HEAD SET SCREWS • HEX JAM SCREWS • LONG ARM HEX KEYS • NYLON PATCH • LOW HEADS 6-LOBE (TORX) KEYS • BUTTON FLANGE CAP SCREWS

Please visit us at www.SetkoFasteners.com

Setko Fasteners & Distribution 300 N. Klick St. Unit A • Hampshire, IL 60140 Sales@SetkoFasteners.com setkofasteners.com (630) 800-6377

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AD INDEX Able Electropolishing .......................... IBC Boker’s Inc. ................................................49 Ellsworth Adhesives ..............................48

SALES

LEADERSHIP TEAM

Ryan Ashdown

Publisher Mike Emich

rashdown@wtwhmedia.com 216.316.6691

J.W. Winco, Inc. ......................................... 17

Jami Brownlee

Keystone Electronics Corp ....................7

jbrownlee@wtwhmedia.com 224.760.1055

NBK America LLC ...................................IFC

Mary Ann Cooke

Next Level Manufacturing................... 34

mcooke@wtwhmedia.com 781.710.4659

Pivot Point Inc.......................................... 35

Jim Dempsey

Setko Fasteners ...................................... 31

jdempsey@wtwhmedia.com 216.387.1916

Smalley Steel Ring ................................ BC

Mike Francesconi

Würth Industry North America ..........55

mfrancesconi@wtwhmedia.com 630.488.9029

memich@wtwhmedia.com 508.446.1823 @wtwh_memich

Managing Director Scott McCafferty

smccafferty@wtwhmedia.com 310.279.3844 @SMMcCafferty

EVP Marshall Matheson

mmatheson@wtwhmedia.com 805.895.3609 @mmatheson

Jim Powers

jpowers@wtwhmedia.com 312.925.7793 @jpowers_media

Courtney Nagle

cseel@wtwhmedia.com 440.523.1685 @wtwh_CSeel

NBK America LLC ...................................58 Pivot Point Inc. .......................................59 Smalley Steel Ring .................................60

1 December 202 ring.c om www. faste

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DESIGN WORLD

F O K C I S ?

S G N I R P A N S We were too.

That’s why we are the only manufacturer of Spirolox®.

• Easy and Quick Install/Removal • Interchangeable with Snap Rings • Large Selection from Stock • Easy to Customize Spiral Retaining Rings

Request Free Samples at 847-719-5900 or smalley.com