How to pick up a existing thread for threading.

[D.sebens]

I am making a threaded 1"-14 thread for a tool for work. Doing this on my mini lathe is a slow process! I was about 70% through(by the size not time) when I accidentally made my adjustment in with the cross slide too far in. To make matters worse the lathe was going probably a touch too fast. It stripped the top pinion gear on the leadscrew reverse bar. I have two ordered, would like to keep them plastic so I have a failure point thats easy to replace. Now on to the question, the lathe effectively "jumped time". My thoughts about picking up the thread would be to hand center the tool in the through of the thread, then engage the half nuts, then manually place the thread counter on one of the numbers I am supposed to be using? I'm sure I will have to take some air cuts/VERY light cuts to properly pick the thread up since it probably wont be perfectly centered to what it was before?

Last thing, a guy at work has a harbor freight big die kit. He might have the correct die, I'm about .020-.025" away from target I would imagine the die should be able to handle that. I would imagine that would go much faster than .0005-.001" cuts.


Thanks in advance!

 

[GeneT45]

Back out so you're "cutting air". Wait for your thread dial to come around to the/an appropriate mark and engage half nut. Let the lathe run until the cutting tool is alongside the thread, then stop the lathe (it's OK if it coasts to a halt as long as the tool is still next to part of the threaded area.

Now using only the cross-slide and the compound, and keeping the half-nut engaged, 'steer' your cutter into one of your existing v-grooves. The more accurately you do this, the better your results will be. I like to use magnification, put a white 3x5 card in the background, and shine a light directly on the card. All that done you should be able to guide the tool in nearly perfectly.

Set the cross-slide to '0' - this is your new zero. You can zero the compound if you care to, or just feed in from where it is. Release the half-nut. Now back out the cross-slide, return to the beginning of the cut, advance cross-slide to zero, advance compound by appropriate depth of cut and resume threading.

Takes longer to explain than to do.

GsT

 

[D.sebens]

Seems pretty straightforward, thanks!

 

[SLK001]

GeneT45's method is the way I do it also. Just be sure that your take out the slack in your lead screw like Gene does before realignment.