Chapter 6 Machining Center Carbide Insert Fundamentals 125
when it is necessary to have more than one insert in contact with the work.
A fine pitch is used on workpieces that present an interrupted cut condition.
Increasing the number of inserts on a cutter allows the feed rate (ipm) to
be increased.
Lead Angles
Lead angles on a milling cutter have an effect on cutting force direction,
chip thickness, and tool life. Lead angles can be 0°, 15°, 20°, and 45°. A 0°
lead is used to produce a 90° shoulder. See Figure 6-5. For general milling
applications where rigid conditions exist, 15° and 20° leads are used. A 45°
lead angle allows higher feed rates to be used. As the lead angle increases
from 0° to 45°, the amount of entry shock minimizes. The lead angle will
affect chip thickness. Figure 6-6 shows that as the lead angle changes, the
chip thickness changes as well.
0°
Lead
angle
Chip
thickness
Feed
Lead angle
Actual chip
thickness
Lead Angle Chart
Lead
angle
Actual chip
thickness
0° Feed
(Inches per tooth)
15° 0.96 × Feed
20° 0.94 × Feed
30° 0.86 × Feed
45° 0.707 × Feed
Example: Feed is
0.010″
Lead angle Actual chip
thickness
0° 0.010
15° 0.096
20° 0.094
30° 0.086
45° 0.071
Figure 6-5. An example of an insert with a 0° lead angle,
which is used to create a 90° shoulder. (Kennametal)
Figure 6-6. These charts show that a larger lead angle results in a thinner chip when the feed remains
the same.