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HELP: Single Point Thread Cutting
(DoN. Nichols)
Jon Elson
You might want to try threading at the highest speed you dare run at.
Don
Agreed -- as long as he has an adequate runout groove, so his
stopping point is not too critical. The only time that I thread without
a runout groove is on the CNC machine, where the tool automatically
retracts at the same point each pass. (I've never tried the trick of
threading to a hole, turning the spindle by hand the last turn or so.
That used to be seen on threads on old machine tools.)
Some of the old, old threads did stop on a radial hole. Done by hand, not
under power, by pulling on the flat belts, I presume.
For today's lathe I think the higher speed may produce a better finish--I think
of screw cutting in the back gears (the slowest way) more for larger threads.
If you cut to a groove, then grind your tool blank so as to use only the left
half of the end of the blank, instead of grinding the vee centered on the full
blank. This will allow the thread you form to get further up to the shoulder
of the work.
If you reduce the right end of the work to the minor diameter of the thread
also, this will give you a telltale as to when your toolpoint has reached that
diameter.
Frank Morrison
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