"Tim Williams" wrote in message
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"Ken Davey" wrote in message
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Sounds to me like your 'tool' is too sharp (read no radius).

Wouldn't that be comparable to cutting a flat with a threading tool?

Tim

Yes - cutting a flat with a threading tool produces a "bad surface" but
only if you are in a hurry and want to take a cut or two without
changing the bit. If the tool bit is set correctly this will produce
that bad surface, most likely with a spiral-like cut (a very fine and
uneven thread), when the feed is too fast. A flat can be cut with a
threading tool "point" by feeding really slowly and filing or stoning
the surface afterward. Do this only on a non-essential surface - a shaft
to provide sloppy clearance through a hole... (Called "mulyak
machining")

BTW - I almost always take a very small radius on a threading tool... a
pass or two with a fine stone or even a whitestone - absolute sharp
makes for a possible fracture point under shear...

And, yes, too sharp with no radius could be a part of the problem but
will not totally account for the problem being described as: "metal is
being torn rather than cut"

That description is usually caused by metal being "pushed off" or "torn
off" rather than cut off. The tool being too low (work attempting to
"ride up" onto the top of the too bit) or too high (rubbing under the
cutting surface) produces this. I have also seen this happen with a
"negative rake" on the top of a fairly flat cutting surface.

Remember this for the time you want a (small o.d.) surface to grip with
your fingers to turn and do not have a knurling tool... Tear it out
(it's sharp) then file off the tops of the points ... Not for clients or
others but quick and dirty in your own shop - and cheap...!

JHbs