Thanks for all the helpful advice.
Paul,
I can read most of the metric info on the Sterling picture of the chart. It's very helpful, but, rather surprisingly, 1.25, a very common metric thread, is absent. More research needed.
Hman,
your charts are awesome. I spent a couple of hours testing today and, unfortunately, they are not a match. I'm guessing our leadscrews or gearboxes are different. My leadscrew is described as 7/8" 8 tpi. Your charts have motivated me to find a "gear calculator" for my lathe and I'm working on that.
Stevemetsch,
A very practical recommendation. I contacted Sterling and they said "
Sure come on down. We can contact birmingham for you.
Adam". So, I'm going over there (37 miles from Huntington Beach) in the morning to try and order a manual, as well as take pics of the 1340 chart plates. Very helpful so far.
OK,
I emptied the lathe toolbox and several gears had never been unwrapped. I have 127/120 intermediate, with the following for DRIVER and DRIVEN: 30,36, 40,40 (yes, two), 42. 46, 50, 54, 60, 66.
I found online a pic of a change gear page which looks handwritten-ish, and after trying several of the settings, it appears to work for me. I've been able to produce the 1.25mm thread I needed.
Summary: I hope to get a manual and actual chart plate pics tomorrow and I will definitely figure out all the threading options and print them for easy reference.
Once again, thanks to all for your help. This website is terrific.