I assume that you are running pretty slow, 100 rpm or so,
like we're told is the way to cut threads. I sometimes
wonder if the combination of slow speeds and light feeds
just doesn't prevent the cutting edge from being able to
shear the material cleanly. I've noticed that the best
clean-up pass is .005 or so and at 300+ rpm. But obviously,
it isn't really possible to make a full speed threading cut
up to a face, so maybe you could use a right hand cutting
tool and cut off the end of the part???

Bob Swinney wrote:

Are you sure the helix angle (below the cutting edge) is allowing sufficient
clearance to prevent the tool from rubbing on the bore?

Bob Swinney
"Jim Stewart" wrote in message
...
Charles A. Sherwood wrote:

Are you using cutting oil

Yes, tried lard oil and pipe cutting oil

Are you advancing the compound at 30 degrees or straight in?
Heavy cuts or light cuts?

30 degrees until the end then last fine cut
straight in.

Light cuts. I don't have much choice at 28 tpi


In article ,
Jim Stewart wrote:

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?