Model A 9" stud gear questions
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  1. #1
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    Default Model A 9" stud gear questions

    Hi everyone,

    ive got a 9" model A with standard quick change gearbox...my threading chart says to use the 40T for most everything, and the 20T for the coarsest of threads. i was trying to cut 4TPI and noticed my thread pitch was actually somewhere closer to .175 than .250.....and whats more is that the lathe would not track the same thread even if you engage the half nut on the same number of the dial....ive checked all the gears, there are no missing teeth or anything loose, too much backlash, etc.

    the other strange part is that the actual stud gears that i have are 56T and 40T....no 20?

    the lathe threads just great on the 56T stud gear, and ive used the 40 to cut a 6 TPI screw thread before, and all of that worked out great.

    ive read somewhere that a 20T, 40T, and 56T with the 80T idler were standard for this lathe, but then why do i only have a 56 and 40T stud gear, when the threading chart riveted to the gear box makes no mention of a 56T gear at all? its been a while since ive used this lathe for such coarse threads, but im pretty sure im putting the gears in there correctly. can someone walk me through what small but crucial bit of information im clearly missing!?

    thanks in advance,
    Foose

  2. #2
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    Thumbnail shows the 20, 80 and 56 at work, and the 40 "resting" next to the 56

    Handy stuff to have

    https://bnordgren.org/files/model-a-gears.pdf
    Attached Thumbnails Attached Thumbnails sb-model-end-gears.jpg  

  3. #3
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    The 56 is the gearbox input gear. The 40 and 20 are used on the reverser, the 80 is just an idler, so the number of teeth don't actually matter.

    allan

  4. #4
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    oh man i was way off.....the heck have i been doing with my life?

    im back in the game now though. thanks guys.


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