Smithy Midas 1220 LTD - Manual (Page 74)

Figure 16.3 Using a center gauge, set the threading tool perpendicular to the work piece.
Cutting Right-hand Threads
Place the leadscrew selector in position to feed the cutter from right to left, toward the
headstock. Now you are ready to cut right-hand threads. First, advance the tool so it just
touches the workpiece and turn the compound calibration back to zero. Then, using the
compound feed, feed in the tool 0.002". Next, turn on the lathe and engage the halfnut
lever carefully pushing the handle down. Do not force it, and do not disengage it until you
are completely done.
It is best to take a light, scratch cut first without using cutting fluid. After the tool runs
the desired length, turn off the lathe and back the tool out of the work. Then reverse the
motor to return the tool to the starting position. Using a screw-pitch gauge, check the
thread pitch. The benefit of taking the light cut is that you can correct any mistakes you
might have made.
Figure 16.4 Chamfer the end of the thread to protect it from damage.
It's time to take the real cut now, so apply the appropriate cutting fluid to the work. Feed
the compound feed in 0.005-0.020" for the first run, depending on the pitch of the thread
you have to cut. If you are cutting a coarse thread, start by taking a few heavy cuts.
Reduce the cut depth for each run until it is about 0.002" at the final run. Zero the cross-
feed calibration, then make the second cut.
Workpiece
Toolbit
Center
Gauge
Before
Tool
After
Midas 1220 LTD Operator’s Manual
16-3
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