Tc 9-524 fundamentals of machine tools

Types of Teeth
The teeth of milling cutters may be made for right-hand or
left-hand rotation, and with either right-hand or left-hand
8-4
helix. Determine the hand of the cutter by looking at the face
of the cutter when mounted on the spindle. A right-hand
cutter must rotate counterclockwise; a left-hand cutter must
rotate clockwise. The right-hand helix is shown by the flutes
leading to the right; a left-hand helix is shown by the flutes
leading to the left. The direction of the helix does not affect
the cutting ability of the cutter, but take care to see that the
direction of rotation is correct for the hand of the cutter
(Figure 8-4).
Saw Teeth
Saw teeth similar to those shown in Figure 8-3 are either
straight or helical in the smaller sizes of plain milling cutters,
metal slitting saw milling cutters, and end milling cutters.
The cutting edge is usually given about 5 degrees primary
clearance. Sometimes the teeth are provided with off-set
nicks which break up chips and make coarser feeds possible.
Helical Milling Cutters
The helical milling cutter is similar, to the plain milling
cutter, but the teeth have a helix angle of 45° to 60°. The
steep helix produces a shearing action that results in smooth,
vibration-free cuts. They are available for arbor mounting, or
with an integral shank with or without a pilot. This type of
helical cutter is particularly useful for milling elongated slots
and for light cuts on soft metal. See Figure 8-5.
Metal Slitting Saw Milling Cutter
The metal slitting saw milling cutter is essentially a very
thin plain milling cutter. It is ground slightly thinner toward
the center to provide side clearance. These cutters are used
for cutoff operations and for milling deep, narrow slots, and
are made in widths from 1/32 to 3/16 inch.

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