On Sat, 26 May 2012 09:58:16 -0500, wrote:

K. H. Moltrecht in his book Machine Shop Practice advises: " . . . The
left-hand side-cutting tool should have a 10- to 17-degree relief angle on
the flank below the right side-cutting edge, and an 8- to 12-degree relief
angle below the left-hand cutting edge. . . . ".

Can someone please explain why the 2 respective relief angles should not be
the same ?

Bob Swinney

FWIW, my hand ground HSS thread cutting tool has a bit more than ten
dgree relief on both sides. I've used it for both left and right hand
threads.

Your text is getting at allowing for the slant of the theads. I could
see this being a problem on huge diameter threading.

Karl, still waiting on your apple pick up visit.