Need help diagnosing lathe threading problem

I'm trying to thread on my lathe (an internal thread, but it doesn't matter, I think). My threading dial is broken, so here is how I'm doing it:

- compound at -29 1/2 degrees, boring bar parallel to ways

- made a "scratch" pass to verify tpi (8)

- set cross & compound dials to 0

- advance compound (.025 IIRC), engage half-nuts & make a pass

- stop motor at end of pass, leaving half-nuts engaged

- advance cross slide, reverse motor & back out boring bar, past beginning of thread

- return cross slide to 0, advance compound & make another pass by running motor forward

The problem: I am not picking up the thread! %$%&*^&*...!!!

Nothing is ever dis-engaged, not the half nuts, not the threading-turning selector, not the forward-reverse tumbler, nothing. The motor is run forward & reverse, the cross slide is advanced and returned, and the compound is advanced. The tool post, boring bar, & bit are all tight, as is the chuck on the spindle and the work in the chuck.

What is going on!? The only thing that I can think of is a broken pin in the gear train that is allowing a gear to slip on its shaft. Any other possibilities?

Thanks, Bob

Reply to
Bob Engelhardt
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Wait a minute ... I was wrong - the bit was not tight in the bar. It was slipping back. After tightening it, it's catching the thread properly.

One dope smack for me, Bob

Reply to
Bob Engelhardt

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