Lathes Page: 71
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this tearing tendency. At any time that a bur is seen forming at the
top of the thread, a file should be used to break it down. Figure 64
illustrates the proper method of feeding a 60 tool bit.
b. The following general procedure should be used in the cutting
of a 60 external thread:
(1) Mount roughing tool bit in lathe at center height. Use center
gage to square it to surface of work or to some other surface parallel
(2) Advance tool to surface of work and set thread cutting stop.
Set micrometer dial on cross feed to zero, with handle setting in
such a position that it may be readily and rapidly disengaged
(backed off) by operator.
of cu DOrechon
30 of Feed
FIGU E 64.-Action of threading tool.
(3) By use of compound, advance tool to take a cut of about 0.003
inch, leaving cross feed at its zero setting. With tool clearing end
of work and lathe revolving at proper cutting speed, close split nut
on lead screw, which will cause tool to advance over work to make
first cut for thread.
(4) At point in work where thread is to stop, back tool out of work
by quick turn of cross feed screw and at same time disengage split nut
from lead screw. Return tool point to its starting position, reset cross
feed dial at zero, and advance compound for another cut.
(5) Repeat this process until thread is roughed out to proper
depth for finishing.
(6) Remove roughing tool and insert finishing tool in holder.
Carefully set tool bit to center height and check for squareness with
(7) Engage lead screw and allow tool to travel along work a short
distance away from threaded path. Stop lathe, keeping lead screw
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United States. Army. Air Corps. Lathes, book, November 29, 1940; Washington, D.C.. (digital.library.unt.edu/ark:/67531/metadc96655/m1/73/: accessed November 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.