10k cutting incorrect threads

[sportingrifle]

I am going crazy. What am I missing or is my lathe possessed?
Run this lathe a bit but never cut threads with it before. Trying to cut 12tpi. Set up quick change gearbox what I believe to be correctly as shown in first photo. When I tried it the lathe cuts something like 32tpi!!!! Can’t figure out why. Checked for correct 20 tooth stud gear and 56 tooth leadscrew drive gear-all seems to be in order as in second photo. Any ideas, I am totally stumped. Thanks

 

[sfriedberg]

I apologize if this is too rudimentary, but make sure you are engaging the half-nuts and not the carriage feed. You can see on the chart that each box has both a feed (in inches/revolution) and a thread pitch (in threads/inch). Make sure you are using the lead screw, not the feed shaft.
I note that the 12TPI box on your chart has 0.0284 "/rev, which is equivalent to 35.2TPI.

 

[sportingrifle]

Oh man, I think you nailed it. Embarrassed but relieved. Thank you, buy you a beer if we ever bump into each other.

 

[steve-l]

Oh man, I think you nailed it. Embarrassed but relieved. Thank you, buy you a beer if we ever bump into each other.

Please make sure you know how to use the thread dial indicator when using the half nut.

 

[michiganbuck]

Oregon and BC..Detroit is the middle ground..let me know where you guys wish to stop here for that beer.

 

[sportingrifle]

Please make sure you know how to use the thread dial indicator when using the half nut.

Yes, thank you.

 

[sfriedberg]

Oregon and BC..Detroit is the middle ground..let me know where you guys wish to stop here for that beer.

Buck, we may all three have to meet in Seattle, Boise. Butte or Minot as a central point. Or maybe Calgary or Winnepeg. I'm a lot closer to the inhabited portions of British Columbia than Michigan.