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Abrasives

Hermes Superabrasives CBN and Diamond vitrified bonded abrasives


C o n t en t s

Hermes Group Hermes Group . . . . . . . Hermes SchleifkÜrper GmbH . Quality – our trademark . . . For nature and the environment

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Abrasives Diamond . . . . . . . . . . . . . CBN (Cubic Boron Nitride) . . . . . . The benefits of vitrified bonded CBN and diamond grinding wheels . . . Primary applications for vitrified bonded CBN and diamond grinding wheels . . .

Hermes solutions Internal cylindrical grinding . . . . . . . . . . . Surface grinding . . . . . . . . . . . . . . . External cylindrical grinding . . . . . . . . . . . Roll grinding . . . . . . . . . . . . . . . . .

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The first step to success Your information for us . . . . . . . . . . . . . 13

Hermes Superabrasives identification system Shapes and dimensions . . . . . . . . . . . . 14 Specification . . . . . . . . . . . . . . . . . 16

Application recommendations Process and tool parameters . . Machine parameters . . . . . Cooling lubricants . . . . . . Dressing methods . . . . . . Key data in the grinding process

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Internet Why not visit our website? . . . . . . . . . . .

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H er me s Gr o up

T he Her me s Gr o up The Hermes parent factory was founded in the Lurup district of Hamburg in 1927 and has remained the group‘s head office to this day. Hermes now has over 14 production facilities and subsidiaries in 4 continents throughout the world and for decades, has been a world market leader in the production of abrasives. The map of the world below illustrates our presence and our commitment.

Dr. Siegfried Blankenburg Managing Director Hermes Schleifkörper GmbH, Dresden

Headquarters, Germany

Dear Hermes Customers, I am delighted to take the opportunity presented by the publication of our new "Hermes Superabrasives – CBN and Diamond vitrified bonded abrasives" brochure to thank all our friends and business partners very much for their loyalty to the company.

Hermes Austria

Hermes USA

I would like to assure you that we will continue to do everything we can to satisfy your requirements in full by developing and manufacturing quality products. You may assume that our top priority is always to have satisfied customers. Each day we start afresh, doing everything in our power to achieve this.

Hermes China

Hermes Australia Hermes France

Hermes England

Hermes Germany

With best wishes for our continued partnership in a spirit of cooperation,

Hermes Poland

Hermes Romania

Best wishes

Hermes-China

Dr. Siegfried Blankenburg

Hermes Singapore

Hermes Canada

Hermes USA

Hermes Austria

Hermes Australia


Her me s S c hlei f k ö r per Gmb H

Q uali t y – o ur t r ademar k

On the one hand, we owe a great deal to tradition, but on the other, we are pioneers in the development of innovative products; Hermes places enormous value on the production of high-quality abrasives to the latest state of the art. Hermes vitrified bonded superabrasives are one of the outstanding product strengths of the Hermes Abrasives Group and its worldwide operations. The bonded abrasives activities of the group are bundled in Hermes Schleifkörper GmbH in Dresden, with two production facilities located in Dresden and in Uetersen, near Hamburg. In both plants are working over 160 employees. This means that Hermes Schleifkörper GmbH is the third largest manufacturer of bonded abrasives in Germany. Since 1986, CBN and Diamond bonded abrasives have complemented the innovative range of precision ceramic and resinbonded abrasives, honing rings and PUR-bonded polishing abrasives.

To maintain and expand this high quality standard in future, the TÜV CERT testing body has awarded the Hermes Group the quality seal for satisfying the requirements of DIN EN ISO 9001:2000 and thus confirmed it. Hermes is a founder-member of the Organisation for the Safety of Abrasives – oSA, the members of which have undertaken to manufacture and sell safe bonded abrasives which prevent accidents. Hermes Superabrasives accordingly satisfy all the safety requirements of DIN EN 13236 : 2001 and all the precision requirements of DIN ISO 22 917. Our customers - in other words you - derive great benefit from this security.

F o r n a t ur e an d t he en v ir o nmen t

Compliance with national and international laws and regulations is one of the most important principles of Hermes‘ environmental policy. The "Environmental protection" department at Hermes takes painstaking care to ensure that every business process saves natural resources. This makes protection of the environment a cornerstone of Hermes‘ commercial policy and a key component of our corporate responsibility.


A b r a si v e s

Diamond Diamond has the greatest hardness and resistance to wear of all known substances and is therefore suitable for machining (grinding) hard and brittle materials such as hardened metal, cermets, glass and ceramic. Syntheticallyproduced diamond is mainly used for abrasives nowadays. The starting material is carbon (graphite) which, under the effects of temperature, pressure and catalysts, is synthesized into the diamond crystal lattice. Diamond has a high affinity for carbon, i.e. carbon-containing material such as steel draws carbon out of the diamond under the action of heat, destroying the crystalline structure of the diamond in the process. Diamond is therefore suitable only in special cases, if at all, for the economic grinding of steels and grey cast iron.

Kohlenstoff-Atom Carbon atom

Material properties Hardness

10 on the Mohs scale

Crystal morphology

Thermal conductivity

the highest of all substances at room temperature

The possible shapes (morphology) of synthetic diamond crystals extend from the cube to the octahedron.

Coefficient of friction

extremely low

Chemical resistance

to acids and bases up to 800 °C

Density

3,51 g/cmÂł

Chemical symbol

C

Unit of weight

carat (1 carat = 0.2 g)

Oktaeder Octahedron

WĂźrfel Cube

The benefits of vitrified bonded CBN and Diamond grinding wheels In contrast to other bond systems, it is possible to dress vitrified bonded grinding wheels (reset the bond) without subsequent sharpening which is why the dressing process can be both reproduced and automated. In the production of these bonded abrasives, the porosity of this material can be set from closed to very open. Among other features, the optimized porosity of vitrified bonded CBN and Diamond grinding wheels means that they also generate cool grinding because the pores guide the cooling lubricant to the point of grinding and transport the chips which form away from the contact zone. Specific adjustment of the volumetric ratio between abrasive and pores allows grinding forces to be kept low and higher performance parameters to be achieved in the grinding process.



The use of materials which are difficult to machine and which cannot be ground economically using conventional abrasives has increased significantly in recent years. More and more steels produced by the powder metallurgy method are being used, for example and these are ground with vitrified bonded CBN grinding wheels; the use of hardened metals and oxide ceramics is also increasing and consequently so is the use of vitrified bonded Diamond grinding wheels.


CBN (Cubic Boron Nitride) CBN (Cubic Boron Nitride) has the same crystalline structure as diamond and is therefore likewise extremely hard. In CBN, boron and nitrogen atoms, rather than carbon atoms, form the crystal lattice. Cubic boron nitride does not occur in nature and is therefore produced only synthetically in a similar process to that for synthetic diamond. In 1957, General Electric was the first company to synthesize CBN. Because CBN, in contrast to diamond, is free of carbon, it is particularly suitable for grinding hardened steels containing carbon. Material properties Hardness

9.5 on the Mohs scale

Thermal conductivity

high

Coefficient of friction

low

Chemical resistance

very high

Density

3,48 g/cm³

Chemical symbols

B (Boron), N (Nitrogen)

Unit of weight

carat (1 carat = 0.2 g)

Boron atom Boratom

Nitrogen atom Stickstoffatom

Crystal morphology Its more complex atomic structure means that CBN has more crystal shapes. In addition to the shapes between cubes and octahedrons already known from diamond, CBN has other crystal morphologies between octahedra and tetrahedra. Würfel Cube

Oktaeder Octahedron

Tetrahedron Tetraeder

Primary applications for vitrified bonded CBN and Diamond grinding wheels CBN

Diamond

• Iron/carbon materials with a high proportion of alloy which are hard to machine, especially steel; hardness primarily > 55 HRC

• Hard, brittle, short-chipping materials which do not contain iron

• High-speed steel (HSS), cast steel, rolling bearing steel, grey cast iron, stainless steels, tempered cast iron, heat-resistant steels, steels produced by the powder metallurgy method

• Hardened metal, glass, ceramic, quartz, semiconductor materials, plastics, glass fibre-reinforced plastics, natural stone, concrete, composite materials and plastic in general




H er me s s olu t io n s u sin g C B N bo n ded ab r a si v e s

Internal cylindrical grinding Product description Hermes CBN vitrified bonded abrasives for internal cylindrical grinding have proved outstanding in medium to large-scale production. In the course of intensive research work, we have developed an extraordinarily sharp, high-performance bond for internal cylindrical grinding. This bond enables our bonded abrasives to achieve longer tool lifes (chip volume) and its excellent self-sharpening properties reduce grinding times. Bonded abrasives can also be supplied with a steel or hardened metal shaft. Hermes offers customers an additional service of gluing bonded abrasives to shafts provided by the customer (e.g. when abrasive coatings are worn).

Product benefits

Applications

• Considerably reduced dressing times

Specification Operating speed Dimensional example Material Applications

20B 76 M-N4-5 V24 200 63 m/s 1A1W 40 x 55 x 16 - X5 16MnCr5

• Automotive and automotive supplier industry (e.g. rockers, valve bodies) • Transmission engineering (e.g. bores for gear wheels, guide rings) • Electrical industry Specification Operating speed Dimensional example Material Applications

12B 64 X4 V31K 240 63 m/s 1A8 7 x 12 x 4,5 16MnCr5

• Rolling bearing industry • Mechanical engineering (e.g. bores for hydraulic parts, nozzles, bushes) Hermes solutions for rolling bearing races (outer rings) Specification Material

28B 64 X4 V31K 240 100Cr6

Hermes solutions for bore bushes Specification Material



20B 46 P3 V24 175 100Cr6

• Long tool lifes means reduced tool costs • Very good surface qualities • Shorter grinding times increase productivity

Comparison of performance, vitrified bonds 130% 120% 110%

Tool life Standmenge

Hermes solutions for bores

100% 90% 80% 70% 60% 50%

Reference Referenz

V31

V24

> 200 at Konz. beiconc. Konz.<<_200 200 atbei conc. > 200


Surface grinding Product description Hermes surface grinding wheels are characterized by the ideal balance between the three main components: abrasive, pores and ceramic bond. This facilitates cool grinding, high relative metal removal rates and outstanding tool lifes. Hermes surface grinding wheels are vitrified bonded, so can be dressed. They can be used for a broad range of materials requiring machining. CBN bonded abrasives for high-performance surface grinding from 80 m/s operating speed are available with metal core bodies.

Product benefits • Prevent thermal overload of the workpiece • Flexible with regard to the material for grinding • Save retooling time • High degree of profile stability • Long tool lifes • Increased productivity • Reduced workpiece costs

Applications Hermes solution for reciprocating grinding Specification Material

23B 126 N6 V24 125 16MnCr5

Hermes solution for creep feed grinding Specification Material

23B 91 N6 V24 100 X155CrVmo12-1




H er me s s olu t io n s u sin g C B N bo n ded ab r a si v e s

External cylindrical grinding using the Quickpoint method Produc t description Segmented Hermes Superabrasives for peel grinding allow operating speeds of up to 140 m/s. Their outstanding grinding properties were achieved by a newly-developed, vitrified bond matrix in conjunction with specially-selected CBN grit qualities. The tools are used on Junker‘s Quickpoint machines, for example. Hermes solutions for high-performance peel grinding Specification Operating speed Dimensional example Material Workpiece

23B 126 R4 V241 161 125 m/s 3A1 400/J297,5 x 25 x 127-U8-X5 tempering steel, sintered metal camshaft

Specification Operating speed Dimensional example Material Workpiece

10B 126 T3 V42 161 125 m/s 3A1 406/J342 x 18 x 127-U6-X8 tempering steel camshaft

Produc t benefit s

A pplications

Productivity comparison

Diagram illustrating the principle of peel grinding

% 140 120

Direction of grinding

100 80

Grinding radii

60

External cylindrical grinding

Surface grinding

40 20 0

Standard bond

• Long tool lifes • Considerably reduced dressing times • Low wear on grinding wheels • Increased productivity • Very good surface qualities

V241 Grinding grooves and infeeds

• Automotive and automotive supplier industry • Cutting tool industry • Transmission engineering • Machine tool engineering • Textile machine engineering • Printing press engineering • Electrical industry

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External cylindrical grinding of crankshafts Produc t description Hermes crankshaft grinding wheels with segmented CBN coatings can be manufactured in external diameters up to 750 mm. Further optimization of high-performance bond V24 has significantly improved grinding properties. The significantly increased profile stability of the CBN coating in particular leads to shorter grinding times and longer tool lifes. Hermes Superabrasives for external cylindrical infeed grinding can be used at operating speeds of up to 160 m/s. Hermes solutions Specification Operating speed Dimensional example Material

30B 126/181 R6/T6 V04 150/125 Sandwich design 125 m/s 1L1-450 x 24 x 127-U21--R1.8-X5 tempered steel

Specification Operating speed Dimensional example Material

23B 151 N7 V241 161 125 m/s 3A1-600/J275 x 40 x 140-U20-X8,5 tempered steel (e.g. 16MnCr5)

Produc t benefit s • Prevent thermal overloads on the workpiece despite extremely high metal removal rate • Save retooling time • High degree of profile stability • Long tool lifes • Increased productivity from reduced workpiece costs

A pplications • Grinding pins and journals on crankshafts Also: • Grinding bearing seats on transmission shafts • Other external cylindrical infeed grinding processes with extremely high Requirements with regard to reduced grinding time with tightest adherence to surface and dimensional tolerances on the workpiece

External cylindrical grinding of pump cams Grinding process Workpiece Operating speed Material

Hermes solution pump cams on camshafts 125 m/s 16MnCr5 (1.7131), 58 HRC

Specification Dimensional example

23B 126 M7/6 V241 125 Shape 14A1 400/J192 x 27 x 127-U25-X5

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H er me s s olu t io n s u sin g C B N bo n ded ab r a si v e s

Roll grinding Produc t description High-alloy materials require suitable high-performance abrasives for roll grinding. Our newly-developed CBN grit mixture meets this need. The performance potential of CBN required is exploited to the full in combination with a high-performance bond. Hermes solutions for high-performance peel grinding Specification Operating speed Dimensional example Material

73B 107 P7/6 V04 100 50 m/s 1A1-600 x 40 x 203,2-X3 e.g. ASP 2023

Product benefits • Surfaces are stable in the long term, yet can have varying designs (adjustable by means of the appropriate dressing and grinding parameters) • Save retooling time • Generate surfaces without twists or patterns • Long tool lifes • Increased productivity

Applications • Working and back-up rollers in cold-rolling applications • Highly suitable for servicing Sendzimir stands • Grinding high-alloy, wear-resistant steels, e.g. high-speed tool steel with 12% Cr (e.g. 1.2379) and high-performance high-speed steel produced by the powder metallurgy process (ASP 2023)

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T h e f ir s t s t ep t o s uc c e s s

Your information for us Note Your process data and optimization objectives form the basis for us applying our expertise and thus for our shared success. Please fax the form to +49 (0)351 2801-390 Company name

Address Street Town/Postcode Shape and dimensions of grinding wheel (if not ISO standard, please send a drawing as well)

Grinding method (e.g. surface, internal cylindrical or external cylindrical grinding)

Grinding machine

Operating speed v C in m/s or grinding spindle speed of rotation n S in rpm Description of workpiece (e.g. valve)

Material, hardness of material

Surface quality required (R a or R z or R t in Âľm) Grinding overmeasure, infeed control in mm

Wet or dry grinding

Specification used to date

Optimization objective

Annual requirement for this item

13


H er me s S uper ab r a si v e s I den t i f ic a t io n S y s t em

Shapes and dimensions 14L1R

D/J

Shape of wheel

Diameter of wheel

x

T

x

Thickness of wheel

H

- U - R - X

Bore diameter

Coating dimensions

Core body basic shape

Grinding coating shape

14

L

1

2

A

AA

B

BF

3

4

BT

C

D

E

6

9

EF

ET

F

GN

K

L

M

Q

60째

10

11

<= 30째

12

14

14

>30째 to <60째

13


The shapes of CBN and Diamond bonded abrasives are described in DIN standard 69 800. The shapes of grinding wheels are described by means of 4 primary characteristics: 1. Basic shape of core body; 2. Shape of grinding coating; 3. Arrangement of grinding coating; 4. Modification.

Arrangement of grinding coating

Modification

1

R

1

2

OnUmfangseitig circumference

On the side, one side Seitenfläche einseitig

3

4

On the side, two sides Seitenfläche zweiseitig

5 Outer chamfer or outerBogen curve Außenfase oder äußerer

Inner chamfer or inner curve Innenfase oder innerer Bogen

6 Part theUmgangsfläche circumferential surface Teilofder

7

8

Part side surface Teilof derthe Seitenfläche

Continuous Durchgehend

B

C

H

Senkung fürfor Countersink cylinder Schrauben bolts zylindrische

Senkung fürfor Countersink countersunk bolts Senkschrauben

DurchgangsContinuous bores bohrungen

M

P

R

Durchgangsund Continuous and Gewindebohrungen threaded bores

Belag relieved einseitig on Coating ausgespart one side

Belag beidseitig Coating relieved on ausgespart both sides

Q

Y

V

Innenliegend Inside

Innenliegend Concave on inside konkav

Konkaver Concave coating Belag

W W Mit

K WithKeilnut keyway Mit

NEW

NEW

9

10

Corner Ecke

Inside Innen

Schaft oder Spindel With shaft Mitor spindle Schaft oder Spindel

S

SS

Segmented

Segmented and slit

15


H er me s S uper ab r a si v e s I den t i f ic a t io n S y s t em

Specification (e.g. 23B 126 P5 V241 150 125 m/s) Manufacturers mark vitrified bonded CBN and Diamond abrasives in accordance with a company-specific code. On the following pages, we show the Hermes Identification System using the example specification mentioned above.

Type

Grit type

Grit size and surface quality

23 B

126

Application

FEPA

Nominal mesh width [µm]

US-Mesh

RZ [µm]

Rt [µm]

Ra* [µm]

6.3

6 - 12

10

8 - 15

3000

0.17

0.10 - 0.30

0.02

1800

0.30

0.20 - 0.50

0.04

25

20 - 30

800

0.43 0.52

0.30 - 0.70 0.40 - 0.80

0.06 0.08

46

38 - 45

325/400

0.65

0.50 - 1.00

0.10

64

53 - 63

230/270

0.77 0.86

0.60 - 1.20 0.65 - 1.40

0.12 0.14

76

63 - 75

200/230

1.00 1.07

0.70 - 1.60 0.80 - 1.70

0.16 0.18

91

75 - 90

170/200

1.20

0.90 - 1.90

0.20

107

90 - 106

140/170

1.45 1.70 1.95

1.10 - 2.30 1.30 - 2.70 1.50 - 3.00

0.25 0.30 0.35

126

106 - 125

120/140

2.20 2.45

1.70 - 3.40 1.90 - 3.80

0.40 0.45

151

125 - 150

100/120

3.45 4.60

2.70 - 5.20 3.70 - 7.00

0.65 0.90

181

150 - 180

80/100

5.45 6.35

5.20 - 9.50 4.50 - 8.20

1.10 1.30

213

180 - 212

70/80

7.10

6.00 - 10.00

1.50

301

250 - 300

50/60

8.45 11.20 15.10 19.40 20.60

7.10 - 12.50 9.60 - 16.50 13.00 - 22.00 17.00 - 28.00 18.00 - 30.00

1.80 2.50 3.50 4.50 5.00

CBN 11B 29B

High performance e. g. for external cylindrical and internal cylindrical grinding

12B 22B 28B

High performance e.g. for internal cylindrical grinding

13B 16B 23B

High performance e.g. for external cylindrical and surface grinding

10B 20B 30B

Standard e.g. for external cylindrical, internal cylindrical and surface grinding

Diamond 12D 14D

High performance e.g. for external cylindrical, internal cylindrical and surface grinding

10D 11D

Standard e.g. for external cylindrical, internal cylindrical and surface grinding

External cylindrical method, further dependent on dressing conditions, materials. This information is only intended as a guide! The surface values which can be achieved are significantly affected by the grinding method, the conditions of use and the concentration of hard substance in the coating specification. * CLA (Centre Line Average) RMS (root mean square average)

16

[µ" ] = R a [µm] / 0.0254 [µ" ] ~ CLA [µ" ] / 0.85


Code letter

Hardness

H, I, JOT, K

Hardness

Structure

P

5

Use

Code numbers

Description

soft

primarily for heat-sensitive materials

2-3

dense structure

L, M, N, O

medium

standard

4-7

medium structure

P, Q, R, S

hard

for very good profile and edge stability

8 - 10

open structure

T, U, V, W, X

very hard

for high profile and edge stability (e.g. Quickpoint)

Number / 2 ... 8

with artificial pore-former

Explanation of surface values 1

2 R Z2

3

Rt

5 R Z4

R Z1 Ra

4

R Z3

R max

R Z5

Reference profile Actual profile Mean profile

Base profile Area

Ra Rz Rt R max

arithmetical mean roughness value averaged surface roughness maximum surface roughness maximum individual surface roughness

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H er me s S uper ab r a si v e s I den t i f ic a t io n S y s t em

Specification (e.g. 23B 126 P5 V241 150 125 m/s)

Name V04

Bond

Concentration

V241

150

Hardness Grinding process

Concentration

Per cent by volume of diamond/CBN

Moderate Universal

CBN in carat/cm3

Diamond in carat/cm3

V31

Internal cylindrical grinding

25

6.30%

1.09

1.10

V24

Internal cylindrical and surface grinding

50

12.50%

2.17

2.20

V42

External cylindrical grinding

75

18.80%

3.26

3.30

V242

Internal cylindrical grinding

100

25.00%

4.35

4.40

V41

External cylindrical and surface grinding

125

31.30%

5.44

5.50

150

37.50%

6.53

6.60

175

43.80%

7.61

7.70

200

50.00%

8.70

8.80

220

55.00%

9.57

9.68

240

60.00%

10.44

10.56

V241

18

Extremely External cylindrical grinding e.g. cam shape strong


Permitted circumferential speed

Maximum operating speed (m/s)

125 m/s Number of stripes

below 50

none

50

1x blue

63

1x yellow

80

1x red

100

1x green

125

1x blue + 1x yellow

140

1x blue + 1x red

Coding colour of stripes

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A p plic a t io n r ec ommen da t io n s

Influence of process and tool parameters on outcome Grinding force (y) Grindability of steel (x)

high

high

y

y

y

y

difficult

x

easy

low

difficult

x

easy

low

y

y

y

y

low

x

high

low

low

x

high

low

low

x

high

low

high

high

high

high

y

y

y

y

low

x

high

low

low

x

high

low

low

x

high

low

high

high

high

high

y

y

y

y

poor

x

high

low

poor

x

high

low

poor

x

high

low

high

high

high

high

y

y

y

y

low

x

high

low

low

x

high

low

low

x

high

low

high

high

high

high

y

y

y

y

low

x

high

low

low

x

high

low

low

x

high

low

high

high

high

high

y

y

y

y

low

Hardness (x)

low

high

low

Grit size (x)

easy

high

low

Concentration (x)

x

high

low

Effective roughness from dressing (x)

difficult

high

low

Lubricity of cooling lubricant (x)

Burning risk (y)

high

low

Metal removal rate (infeed control, feed rate) (x)

Roughness (y)

high

low

Cutting speed (x)

Wear (y)

low

x

high

low

low

x

high

low

low

x

high

low

high

high

high

high

y

y

y

y

low

low

x

high

low

low

x

high

low

low

x

high

low

difficult

x

easy

low

x

high

low

x

high

poor

x

high

low

x

high

low

x

high

low

x

high

low

x

high

Structure

Structure is specified mainly by the process and should only be varied within narrow limits. In general, it holds true that the longer the contact length, the more open the structure (the higher the structure number).

Bond

Hermes uses the bond best suited to the process.

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Selecting machine parameters for CBN grinding Grinding process and machine parameters

Settings

External cylindrical grinding Traverse grinding Cutting speed vC

30 - 140

m/s

Workpiece speed vW

15 - 200

m/min

Workpiece advance v t

0.5 x bS x nW mm

Infeed ae

0.005 - 0.05

mm

Cutting speed vC

30 - 140

m/s

Workpiece speed vW

100 - 200

m/min

Advance speed v fr

0.1 - 2.0

mm/min

Plunge grinding

Centerless grinding Cutting speed vC

30 - 100

m/s

Workpiece speed vW

30 - 150

m/min

Workpiece advance v t

50 - 2000

mm/min

Infeed ae

0.005 - 0.05

mm

Surface grinding Reciprocating grinding Cutting speed vC

25 - 60

m/s

Workpiece speed vW

10 - 20

m/min

Infeed ae

<= 20% of grit size

Crossfeed

0.5 x bS

mm

Internal cylindrical grinding Oscillation grinding Cutting speed vC

15 - 80

m/s

Workpiece speed vW

30 - 120

m/min

Infeed ae

0.001 - 0.02

mm

Crossfeed

Short-stroke oscillation

Plunge grinding Cutting speed vC

35 - 80

m/s

Workpiece speed vW

60 - 120

m/min

Advance speed v fr

0.1 - 2.5

mm/min

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A p plic a t io n r ec ommen da t io n s

Cooling lubricants Note In principle, vitrified bonded CBN/diamond abrasives should be used only in wet-grinding methods. Conventional cooling lubricants perform the tasks "lubricate", "cool" and "flush" to varying degrees of satisfaction. A distinction is generally made between three types of cooling lubricants.

1. Grinding oils with EP additives In addition to their cooling action, their good lubricating properties have a favourable impact primarily on friction forces, thus allowing longer tool lives to be achieved for better surface qualities.

2. Emulsions (water with 0.2 - 15% oil fraction) Good wettability, high level of heat dissipation and consequently good cooling action. Suitable for CBN and diamond grinding wheels at elevated metal removal rates and moderate roughnesses.

3. Transparent solutions of synthetic products with EP additives In addition to good wettability, their transparency should be mentioned as a particular benefit. It allows the grinding process to be observed better. Suitable for CBN and diamond grinding wheels at elevated metal removal rates and moderate roughnesses. Product comparison Cooling lubricant

Lubricating action

Cooling performance

Cleaning effect

Resistance to ageing

Mineral oil, pure

very good

poor

moderate

good

Emulsion 15%

good

moderate

good

poor

Emulison 5%

moderate

good

good

moderate

Synthetic solution 3%

poor

very good

very good

very good

Semi-synthetic solution 3%

good

good

good

good

Material

Abrasive

Grinding process Cooling lubricant Recipro- Creep recommended cating feed grinding grinding

Hardened metal Hardened metal + steel Ceramic Spray-on alloys with tungsten carbide

Diamond

HSS Chrome steel Metal spray-on alloys

CBN

Long-chipping types of steel e.g. 100Cr6, 16MnCr5

CBN

Comparison of applications

Special materials 22

X X X X X X X X X X X

X

Water fraction

Emulsion Emulsion Fully-synthetic solution Semi-synthetic solution

98 - 95% 95 - 90% 98 - 97% 98 - 97%

Emulsion Fully-synthetic solution Semi-synthetic solution Fully-synthetic solution Semi-synthetic solution Mineral oil with EP if appropriate

98 - 95% 97 - 95% 97 - 96%

Emulsion Mineral oil with EP if appropriate

95 - 80%


Dressing methods and parameters Note It is generally necessary to dress the bonded abrasive after changing the tool (to generate concentricity) and during the grinding process once the tool life criterion (surface quality, profile deviation) has been reached. Dressing method Diamond profile roller dresser

1

Vfrd

2

Diamond form roller dresser VR

VR

Vfad

Vfrd

Vsd

Vsd

CBN grinding wheel

CBN grinding wheel

3

4

Diamond dressing wheel 7°

VR

Vfad

Vrel = 0

Vfrd

CBN grinding wheel

Steel profile roll

Vsd

CBN grinding wheel

Application recommendations Variables affecting dressing outcome Dressing/speed ratio

Dressing method qd

Semi/counter direction

1, 2, 3

Transverse overlap ratio

Ud =

1, 2, 3

Peripheral grinding wheel speed

vsd

2, 3

Peripheral dresser speed

vR

1, 2, 3

Transverse overlap ratio

Ud

2, 3

Dressing infeed

aed

2, 3

Dressing feed rate

v frd

1, 4

bR

2, 3

Contact pressure Dressing contact width

Formulae

Dressing/speed ratio

bR . n vfad sd

v qd = R vsd

4

Recommended settings for dressing methods 2+3 qd > 0.5 aed = 2; aed â&#x20AC;&#x201C; total = max. 10% of grit diameter Ud = 5 (Ud : number of times dressing tool contacts a point on the circumferential surface of the abrasive tool)

23


A p plic a t io n r ec ommen da t io n s

Dressing methods and parameters Effect of speed ratio and dressing infeed on effective surface roughness 16

14

12

frd = 0.72 frd = 0.54 frd = 0.36 frd = 0.18

Effective surface roughness (Âľm)

10

8

6

4

2 Semi direction 0

2

1.5

Counter direction 1

0.5

0 Speed ratio q

-0.5

-1

-1.5

Source: Schmitt, R. â&#x20AC;&#x201C; Dressing grinding wheels with diamond-coated rolls - dissertation from the Technical University in Braunschweig, Germany

24

-2


Key data in the grinding process G ratio The G ratio allows a direct comparison to be made between two different grinding wheels in the same grinding process with identical parameters. The ratio is calculated as follows:

G =

volume of workpiece removed [mm3] wheel coating consumed [mm3]

General guidelines Diamond on hardened metal

CBN on HSS

50 - 300

150 - 800

Relative metal removal rate Q'W

The relative metal removal rate describes the removal rate of a grinding wheel per second per millimetre of grinding wheel thickness. This allows a direct comparison of different grinding processes to be made. Formulae for calculating Q'W [mm3 /mm . s]:

Q'W = Q'W =

Q'W =

ae . vt

Surface and creep feed grinding

60 ae . nW . DW . Ď&#x20AC; 60 v f . DW . Ď&#x20AC; 60

External cylindrical longitudinal grinding

Key ae

Infeed control [mm]

v t

Advance speed [mm/min]

DW Diameter of workpiece [mm] nW Speed of rotation of workpiece [rpm] v f

Radial advance speed [mm/min]

External cylindrical infeed grinding

25


I n t er n e t

W h y no t v i si t o ur w eb si t e ?

The Hermes Group website is constantly being updated and is an important information platform. We very much look forward to your visit.

Virtually all the information useful for planning and purchasing Hermes abrasives is available on the Hermes website which is based on a database and is equipped with numerous other functions:

It goes without saying that the Hermes site is bilingual (German and English), so it can be used all over the world.

• New products • Product finder with detailed information • Information about the Hermes Group

www.hermes-abrasives.com

You have the option of ordering information material via the Web or downloading it for instant availability. Our website also shows you all the relevant contacts – both field and office-based staff. 26


For more information about Hermes bonded abrasives:

Hermes SchleifkĂśrper GmbH LohrmannstraĂ&#x;e 21 01237 Dresden, Germany Tel. +49 351 28 01-0 Fax +49 351 28 01-390 hsr@ hermes-schleifmittel.com www.hermes-abrasives.com

33 E 70.40 . The right to make amendments is reserved


Hermes SuperAbrasives  

Technische informatie van speciale slijpstenen

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