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Need 20t stud gear for 9a or options

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Steelcrafted

Swarf
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#1
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...

IMG_20180613_213155601.jpg

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
 

dtsh

H-M Supporter - Sustaining Member
H-M Supporter - Sustaining Member
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Sep 22, 2017
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#3
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).
 

coffmajt

H-M Supporter - Sustaining Member
H-M Supporter - Sustaining Member
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#6
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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