LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
Improperly ground angles will result in weakening and breaking the cutting
edge and overheating the bit.
d.
Recommended Clearance and Rake Angles. Table 1 on the following page
lists the clearance and rake angles for various materials that are to be
machined. When grinding cutter bits, the lip angle should he considered in
selecting the proper angles from the table.
e.
Common Types Of Cutter Bits.
(1) General.
Cutter bits (figure 12 on page 28) are made from standard
sizes of bar stock to fit into cutting toolholders which in turn are
fastened to the toolpost of the lathe. If the cutter bit is to be used for
heavy roughing, where a finished surface is not expected, the nose should be
ground with a very small radius (approximately 1/64 inch).
If the cutter
bit is to be used for general shaping and finishing, the nose should be more
rounded (approximately 1/32-to 1/16 inch radius). The following cutter bits
are identified by their function.
(2) Right-Hand Turning Cutter Bit.
The right-hand turning cutter bit is
shaped to be fed from right to left. The cutting edge is on the left side
of the bit and the face slopes down away from the cutting edge. The left
side and the end of the tool are ground with sufficient clearance to permit
the cutting edge to bear upon the workpiece without the heel of the bit
rubbing against the workpiece. The right-hand turning cutter bit is ideal
for taking light roughing cuts as well as general all-around machine work.
(3) Left-Hand Turning Cutter Bit.
The left-hand turning cutter bit
(figure 12) is just the opposite of the right-hand turning cutter bit, being
designed to cut the metal when fed from left to right. It is used for all
around machine work when right-to-left turning is impractical.
(4) Round-Nose Turning Cutter Bit.
The round-nose turning cutter bit
(figure 12) is used for all around machine work and may be used for taking
light roughing or finishing cuts. Usually the face is ground with a right
sloping side rake so that
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