Need some help understanding threading gearsets on a Seneca Falls Star 30

Be careful when selecting and installing change gears for threading. I had been using this machine for several years before I decided to purchase a new chuck and make a back plate. Before cutting the threads on the new back plate I thought it would be a good idea to make a plug to check the thread depth. I looked at the chart, installed what I thought were the correct gears and began threading an aluminum plug to 1 7/16-12.

When I was close to finished dimensions I took another chuck and attempted to screw it on the plug. I was frustrated when it wouldn't thread on. Thinking I needed the thread depth to be more exact I completed the plug. Still it was a no go. I scratched my head and measured the thread depth again. Still nothing. I must have fooled with the lead thread, depth of thread, possible burrs in the chuck, and anything else I could think of for nearly an hour.

Finally I got out the thread gauges and placed the 12 tpi against the threads. It fit sorta, but not really. That's when I realized I'd put the gears on for an 11 1/2 tpi thread. Close, but no cigar. All that time and all that work for a 1 7/16-11.5 tpi thread that fits absolutely nothing. I've never needed a thread of that size, and don't know of anything that uses it. However I did learn a valuable lesson. Check and double check the gear configuration before turning any threads. In this case I only wasted a plug of aluminum and an hour or so of time. Had I started threading the backing plate I would have had to start all over.

As a reminder I keep the plug in a prominent place to remined me to measure twice, cut once.
 
I'm not sure I totally agree with John about instant-reversing motors being better, they do introduce the possibility of spinning off the chuck if one is not careful. He is correct about everything else though

I practice the "A" technique mentioned by Projectnut; I shut off the motor and let it coast before reaching the shoulder, with practice you can get pretty good at it without crashing your threading tool
 
This may help........https://www.hobby-machinist.com/threads/seneca-falls-star-30-lathe-resto-mod.68221/
 
Drum switch came in and I spent the day figuring out which contacts did what to who (no instructions), making a bracket for it and wiring it. Works like a champ.

As to coasting to a stop, I don't see an issue. I'll be in back gear when threading and it's turning slow enough that it doesn't even make a full revolution before stopping and that's running free. Should be even faster with when making a cut.

Now to get a threading cutter and make some chips.

Thanks to everyone for the advice and help!
 
An old dog just learned a new trick. In my previous post I noted that I'd made a mistake with change gears when cutting a thread and mentioned: "That's when I realized I'd put the gears on for an 11 1/2 tpi thread. Close, but no cigar. All that time and all that work for a 1 7/16-11.5 tpi thread that fits absolutely nothing. I've never needed a thread of that size, and don't know of anything that uses it."

Well today I finally found where an 11.5 tpi thread is used. Believe it or not it's a common garden hose fitting. I have to make an adaptor to force Marine Antifreeze into the pump on my new pressure washer. Today I'm making a fitting that attaches to a 1 gallon plastic bottle on one end and a garden hose on the other. I know it's a little early to worry about winterizing, but I finally got the deck finished and it's time to play in the shop for an hour or so.
 
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