Husqvarna 371K Workshop Manual Supplement page 17

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CUTTING DISCS
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 Euro-
pean 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 hand-
held 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.
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