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- Parts made of soft material or plastic (light alloys,
mild bronze, Teflon, wood, etc.) also require
widely spaced tooth;
- Pieces cut in bundles require combo tooth design.
8.3 Teeth pitch
As already stated, this depends on the following
factors:
- Hardness of the material
- Dimensions of the section
- Wall thickness.
8.4 Cutting and advance speed
The cutting speed (m/min) and the advance speed
2
(cm
/min =area traveled by the disk teeth when
removing shavings) are limited by the development
of heat close to the tips of the teeth.
- The cutting speed is subordinate to the resistance
of the material (R = N/mm
and to the dimensions of the widest section.
- Too high an advance speed (= lowering of the saw
frame) tends to cause the disk to deviate from the
ideal cutting path, producing non rectilinear cuts
on bath the vertical and the horizontal plane.
The best combination of these two parameters can
be seen directly examining the chips.
Long spiral-shaped chips indicate ideal cutting.
Very fine or pulverized chips indicate lack of feed
and/or cutting pressure.
Thick and/or blue chips indicate overload of the
blade.
8.5 Blade running-in
When cutting for the first time, it is good
practice to run in the tool making a series of
cuts at a low advance speed (= 30-35 cm
material of average dimensions with respect to the
cutting capacity and solid section of normal steel
with R = 410-510 Nimm
the cutting area with lubricating coolant.
2
), to its hardness (HRC)
2
/min on
2
). Generously spraying
8.6 Blade structure
Bi-metal blades are the most commonly used. They
consist of a silicon-steel blade backing by a laser
welded high speed steel (HHS) cutting edge. The
type of stocks are classified in M2, M42, M51 and
differ from each other because of their major
hardness due to the increasing percentage of
Cobalt (Cc) and molybdenum (Mo) contained in the
metal alloy
8.7 Blade type
They differ essentially in their constructive
characteristics, such as:
- Shape and cutting angle of tooth
- Pitch
- Set
Shape and angle of tooth
REGULAR TOOTH: Oº rake and constant pitch.
Most common form for transversal or inclined
cutting of solid small and average cross-sections or
pipes, in laminated mild steel and gray iron or
general metal.
POSITIVE RAKE TOOTH: 9º - 10º positive rake
and constant pitch.
Particular use for crosswise or inclined cuts in solid
sections or large pipes, but above all harder
materials (highly alloyed and stainless steels,
special bronze and forge pig iron).
COMBO TOOTH: pitch varies between teeth and
consequently varying teeth size and varying gullet
depths. Pitch varies between teeth, which ensures
a smoother, quieter cut and longer blade life owing
to the lack of vibration.
Another advantage offered in the use of this type of
blade in the fact that with an only blade it is possible
to cut a wide range of different materials in size and
type.
COMBO TOOTH: 9º - 10º positive rake.
- 13 -
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