Cutting discs

Rating plate

All Husqvarna power cutters are fitted with a plate on the guard that provides valuable information when selecting cutting discs for a machine. The measurements that the operator should be familiar with are as follows:

Disc diameter

The disc diameter is given in mm or inches. Husqvarna 371K Air Injection can be used with the following cutting discs: 12" (300 mm), 14" (350 mm) or 16" (400 mm). Husqvarna 3120K Air Injection can be used with the following cutting discs: 14" (350 mm) or 16" (400 mm).

Centre diameter

The size of the mounting hole in the cutting disc must match the diameter of the bushing on the drive shaft exactly. There are various standards depending on the country the machines are sold in. Common standard diameters are 20.0, 22.2, 25.4 (1") and 30.5 mm. Replaceable bushings are available for Husqvarna power cutters for all these diameters.

Speed

All cutting discs are marked with a speed that is usually measured in revolutions per minute (rpm). This is the maximum speed of rotation of the disc. The maximum speed of a disc is determined by the disc manufacturer. The rating plate on the power cutter gives a different speed that is determined by the machine manufacturer and is known as the rated speed. The rated speed is the speed given on the rating plate and it determines what speed rating a disc must have in order to be used with the power cutter. A cutting disc must be rated at the same speed or a higher speed than that given on the machine’s rating plate. The maximum speed of the machine is a measurement that does not concern the machine operator and is not even stated on the machine, but is used for inspection purposes by the workshops. The maximum speed is the highest permissible speed that the drive shaft may reach with no load on the disc and the engine at full throttle. According to a European standard the maximum speed must not exceed the rated speed on the machine’s rating plate by more than 10%. For example, a machine with a speed rating of 5,100 rpm must never exceed a maximum speed of 5,100 x 1.1 = 5,610 rpm.

Peripheral speed

Peripheral speed is measured in metres per second and is directly proportional to the rotational speed. The definition of peripheral speed is the speed at which a given point on the edge of the blade travels through the air. It is also the speed that, for example, a given diamond particle will have in relation to the point of contact during cutting. Another way of visualising peripheral speed it to imagine the power cutter as a vehicle, and the cutting disc as its driving wheel. A rotational speed of 5,100 rpm with a 300 mm cutting disc would give the following speed: Circumference of disc: 0.3 m x = 0.94 m. Rotational speed of disc: 5,100 rpm = 85 rps. Circumference x rotational speed = peripheral speed. So the peripheral speed = 0.94 m x 85 rps = 80 m/s. Expressed in terms of a vehicle travelling down a road, this speed is roughly 290 km/hr! Husqvarna cutting discs are designed for a peripheral speed of 100 m/s. A European colour code prescribes a green label for a maximum peripheral speed of 100 m/s, while a red label indicates a maximum speed of 80 m/s.

Types of disc

Hand-held power cutters require cutting discs that are approved for use with handheld power cutters. It is not permitted to use blades intended for bench-mounted power cutters, for example. The speed marking must be equal to or higher than that given on the machine’s rating plate. Husqvarna cutting discs are naturally designed for hand-held cutting. • Diamond blades are a type of cutting disc that is becoming increasingly common for cutting stone, concrete, asphalt and similar materials. The main advantage of a diamond blade is that it maintains practically the same cutting depth throughout its working life and has a high cutting speed. If used correctly it is a very economical blade. Husqvarna sells diamond blades for professional and occasional users. The range includes several grades, which should be chosen to suit the material to be cut. Diamond blades are available for both wet and dry-cutting.

Abrasive discs, which were originally the commonest type of disc for cutting all materials, are now used mainly for cutting metal. Husqvarna sells abrasive discs for cutting steel and concrete, and its concrete discs are also suitable for cutting soft steel, such as reinforcing bar and structural steel.

Husqvarna Rescue is a special blade with carbide bits. It can only be used by trained personnel in rescue work.

Replaceable disc bushings

Husqvarna power cutters can be fitted with a centre bushing to fit various standard disc sizes. Replaceable bushings are available for 20.0 mm, 22.2 mm, 25.4 mm (1") and 30.5 mm hole diameters. The Husqvarna 371K/3120K Air Injection is supplied as standard with various centre bushings depending on the country of sale.

Which type of disc should I use?

HDC 410

Hard steel Stainless steel Soft steel + other metals Granite Hard brick Pre-cast concrete

Hard concrete General concrete Concrete pipe Abrasive building block Soft brick

Green concrete Asphalt

HDC 500

HDA 900

Steel

Concrete