"Rob McDonald" wrote in message
.. .

snip

I ground a new 60 degree HSS threading tool with 12 deg. relief on both
sides and 10 degrees side and back rake, and stoned the top and sides

smooth. It is mounted directly in a turret type tool post, (i.e. the tool
bit is horizontal, not sloped upward as in a rocker type tool holder).

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2) Any ideas why I ge the rough thread, especially at the right end?

Rob


It is difficult to hand stone a threading tool of this size
without slightly rounding the edge on the last few thou, just where it
matters most. You will finish up with a keener edge by using the tool
as ground or, at most, topface only stoned. A really keen edge is
vital for successfull fine finishing cuts.

Feeding in at 30 deg with 10 deg side and back rake will
generate a slightly incorrect thread form although the error is pretty
small. Top rake should be at 90 deg to the LH cutting edge so that
this edge remains horizontal. Up to 10 deg rake can help particularly
when cutting coarse threads. At 40 TPI zero rake should be OK.

Unless you have overriding strength or wear resistance
requirements your problems would pretty much instantly disappear if
you changed to brass or a free cutting leaded mild steel.

Jim