On Sat, 26 May 2012 16:10:29 +0100, David Billington
wrote:

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
To take into account the helix angle of the thread.

And how do you thread with a side-cutting tool?

--
Ed Huntress