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Need 20t stud gear for 9a or options

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Registered Member
Jun 14, 2018
Hey everyone, I just purchased a 9a precision here locally, I feel like I got a good deal on it, $1,200 with a good amount of tooling, collets, 3 jaw, 4 jaw, collet closers, centers, etc, etc....unfortunately it DIDN'T come with the proper gearing between the spindle and the quick change....The stud gear is a keyed 32, the idler is a 72/18 or 20, and the lead screw gear is a keyed 80...which, it's SUPPOSED to be a keyed 20, an 80 idler, and a keyed 56 on the gearbox, yielding a 4:1 ratio....Unfortunately the only gear I have that is supposed to be in there is a keyed 40t for the stud gear when turning the high thread pitches...here is a pic of the gears as I received them...


So this gearing yield a VERY SLOW lead screw even when trying to thread like 8tpi...I end up at 30ish tpi.....So the best i've been able to come up with is running it 40/72/80 I can get 2:1, which isn't terrible b/c I can just double my pitch in the gearbox and be ok....

BUT, that being said, I need help finding a 20t stud gear, a 56t keyed gear, and an 80t idler....the 80 and 56 i've found on ebay, but NO ONE has a 20t stud.....the closest I can find is a 20t crown gear from inside a quick change that I believe has the same dimensions, but i'm not sure.....

If you all could help that would be great, i'd really appreciate it! Thanks again!

Oh the serial is 42947NAR9


H-M Supporter - Sustaining Member
H-M Supporter - Sustaining Member
Sep 22, 2017
Don't forget to search for gears based on the diametral pitch and tooth count and not just looking for ones specifically for the SB9A, you may find a perfectly suited gear that came from something else. I went through this myself quite recently when addiing a 26t gear to my lathe to gain me several more thread combinations. A 26 tooth gear for the Seneca Falls isn't easy to find as they apparently used a variety of DP sized gears among the models, but I found a clearance Boston gear of the right size which only needed minor modifications to fit (bored to shaft size, face turned down a bit, and a keyway cut).


H-M Supporter - Sustaining Member
H-M Supporter - Sustaining Member
Sep 25, 2013
Another option is to make the gears you need if you have a mill and a rotary table. I needed metric conversion gears for my SB9 and made them using Delrin for the blanks. All I had to find was the correct involute cutter for the correct tooth counts. Good hunting -- Jack
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