Smithy Midas 1220 LTD - Manual (Page 43)

Cutoff, Thread Cutting and Facing Tools
For cutoff, thread cutting, and facing, feed the cutter to the work on dead center (Figure
9.5). For the beginner, the average feed should not exceed 0.002 inches per revolution
(ipr).
Figure 9.5 Feed the cutter on dead center for cutoff, thread cutting and facing.
Boring and Inside Threading Tools
For boring and inside threading, the cutter point engages the work on dead center (Figure
9.6). For greater cutting efficiency, position the bar while parallel to the line of lathe
centers sufficiently below center to give the cutter a 14-1/2 degree approach angle. For
internal threading, grind the top face of the cutter to compensate for this angle, giving a
flat, true form top face.
Some machinists prefer to position the tool slightly above center when boring. With the
bit above center, if a tool chatters it deflects down into empty space instead of into the
workpiece.
Figure 9.6 For boring and inside threading, the cutter point is at dead center.
9: Setting Up Lathe Tools
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