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Similarly, if the workpiece is a soft metal such as
aluminum, each tooth will remove more material
and rapidly fill the blade gullet. For this reason,
use a blade with fewer TPI on soft metals.
An additional problem with an overly fine-pitched
blade is that the pressure each tooth exerts on the
workpiece is reduced. This limits the cutting ability
of the teeth and also results in a buildup of heat
and inefficient cuts.
The ideal blade pitch is one that doesn't overload
individual teeth (too coarse) and avoids excessive
chip buildup in the gullet (too fine) (see Figure 30).
Blade
(Correct TPI
For Workpiece)
Workpiece
Figure 30. Correct TPI.
Damage to the blade, rough cuts, poor cutting
performance, and overheating are all possible
signs of improper blade pitch.
If you feel your machine is not functioning properly
or performing to your standards, check that the
blade pitch is correct for the cut. The procedure
that follows is a basic starting point for choosing
blade pitch (TPI) for standard HSS blades.
-24-
To select correct blade pitch:
1.
2.
D or Th Inches (mm)
<1/16 (<2)
Gullet
Chips
Measure thickness of workpiece.
—For solid workpieces, this measurement is
length of cut taken from where tooth enters
workpiece, sweeps through, and exits
workpiece. See (D) on chart in Figure 31.
—For hollow or profiled workpieces, this
measurement is wall thickness at its thick-
est point (Th).
0.5"
6–8
0.02"
Refer to "D or Th" column of blade selection
chart in Figure 31, and read down to find
1"
4–6
1/16"
workpiece thickness you need to cut. Read
2"
3–4
3/32"
across to find appropriate Pitch (TPI) for cut.
3"
2–3
For blade alternatives, see Accessories on
4"
2
3/16"
Page 27.
5"
.8-1.5
Pitch (TPI)
1/16 (2)
1/8 (3)
1/4 (6)
1/2 (12)
1 (25)
2 (50)
3 (75)
>3 (>75)
Figure 31. Blade selection chart.
G0783 (Mfd. Since 05/15)
8–10
5–7
4–5
1/8"
3.5–4
2
1/4"
.8-1.5
>7
Workpiece
7
6
Measurements
5
Th
O
4
Th
3
D
Th
2.5
<2.5
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