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14
Figure 13-2
Figure 13-3
Figure 13-4
14.0 Blade selection
When using the 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.
14.1 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,
and for soft materials (aluminum alloys and soft
alloys in general).
14.2 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
blades with a coarse
tooth pitch, while small
cross-sections require
blades with finer teeth.
This is because when
cutting walls of small
cross-section (1–7mm)
profiles, it is important
that the number of teeth actually making the cut
should not be too few, 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 3
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.
14.3 Cutting and feeding speed
The cutting speed and the head feeding speed are
limited by the amount of heat generated near to 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.
The cutting speed depends on the strength
(kg/mm
2) and hardness (HRC) of the material and
the dimensions of the thickest section.
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