I find that I can get excellent threads (comparatively) by setting up the
compound parallel to the longitudinal travel. You have to calculate the
depth of thread to go in (I think it's pitch * .6495, in radius, double the
value if your machine is in diameter).

Once you have threaded to this depth (the thread will look incorrect),
retract the compound about .001" and take a pass. Then advance the compound
roughly .002" past your original zero and take another pass. Use thread
measuring wires for the best fit, but you can just muck about with a nut if
you want.

This technique works so well because it independently cuts the leading and
trailing flanks.

I have found the surface grinding the top face of the cutter makes for an
excellent finish. I would assume grinding the side faces couldn't hurt
either.

Regards,

Robin


"Jim Stewart" wrote in message
...
I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?