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11
13.0 Blade Selection
When using the J-FK350 cold saw, it is important
to select the correct type of blade for the material
to be cut. This section explains the limitations and
specific applications of the different types of
blades.
13.1 General Characteristics
Fine Tooth Pitch – used for thin wall materials such
as sheet steel, tubes and profiles
Coarse Tooth Pitch – used for large cross-sections
– for soft materials (aluminum alloys and soft alloys
in general).
13.2 Determining Proper Tooth Pitch
Proper tooth pitch depends on:
a) the size of the section;
b) the hardness of the material;
c) wall thickness.
Solid sections call for
discs with a coarse
tooth pitch, while small
cross-sections require
blades with finer teeth.
This is because when
cutting walls of small
cross-section (1–7
mm) profiles, it is
important that the number of teeth actually making
the cut should not be too small, otherwise the
effect obtained will be one of tearing rather than of
chip removal, leading to a large increase in
shearing stress. On the other hand, when cutting
thick materials or solid sections using an
excessively fine tooth pitch, the chip collects as a
spiral inside the gullet, and since fine tooth pitches
have small gullets, the accumulated chip will
exceed the gullet capacity and press against the
walls of the workpieces, resulting in poor cutting
(same situation with soft materials), greater
shearing stress and hence breakage of the blade.
Table 1
A larger pitch should be chosen when, as a result
of the shape of the piece to be cut, the cross-
section at any given point exceeds the average
cross-section given above.
13.3 Cutting and Feeding Speed
The cutting speed, in m/min, and the head feeding
speed, in cm
2
/min, are limited by the amount of
heat generated near the points of the teeth. If the
head feeding speed is too high, the cut will not be
straight in either the vertical or the horizontal plane.
As we have already said, the cutting speed
depends on the strength (kg/mm
2) and hardness
(HRC) of the material and the dimensions of the
thickest section. The feeding speed depends on
the cross-section of the material. Solid or thick-
walled materials (thickness>5mm) can therefore be
cut at high speed providing there is sufficient swarf
removal by the blade, while thin-walled materials
such as tubes or thin profiles must be cut with a
low feeding speed.
A new blade requires a break-
in period, during which time about half the
normal feeding speed should be used.
13.4 Coolant
The cooling fluid ensures that the blade teeth and
material in the area of the cut do not overheat. The
fluid must be an excellent lubricant so as to prevent
abrasion of the teeth and welding of the chips to
the teeth themselves (seizing).
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