Smithy Midas 1220 XL - Manual (Page 50)

Cutoff, Thread Cutting and Facing Tools
For cutoff, thread cutting, and facing, feed the cutter to the work on dead center (Figure
910.5). For the beginner, the average feed should not exceed 0.002 inches per revolution
(ipr).
Figure 10.5 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
10.6). 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 10.6 For boring and inside threading, the cutter point is at dead center.
Chip Curve
10-3
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Midas 1220 XL Operator’s Manual