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?