Use and Care Manual

12
13.0 Blades
When using the J-CK350 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.
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).
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,
Table 1
resulting in poor cutting (same situation with soft
materials), greater shearing stress and hence
breakage of the blade.
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.
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.
Coolant
The cooling fluid mist 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).
Types of Blades
The blades fitted to the J-CK350 have
dimensions 350 x 32 x 3.4 mm and are of HM
hard steel type since the machine is to be used
for cutting non-ferrous materials. In addition to
the size and pitch of the teeth, however, the
blades also have different geometric
characteristics in accordance with their particular
use:
tooth cutting angle – may be negative or
positive
tooth sharpening – may be BW with an
alternate raked tooth or C with a roughing tooth
raked on both sides and a non-raked finishing
tooth
tooth pitch – the distance between the crest of
one tooth and the crest of the next tooth (tooth
pitch = T)