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  • #63793
    Bob Tascione
    Moderator

      Hi Nic,
      Yes the plate will need 101 holes or any number above that divisible by 101 to cut 101 teeth in the gear.

      So you are saying this would work for most American Pocket watch movements (which are all movements up to 18000 bph) based on your own research with the code you wrote, the code the guy online wrote, and what you had read right

      Yes I believe those numbers would cover most of the gearing needed for the power train on 18,000 American movements. Certainly wouldn’t hurt to do a tooth count on few trains if you have a chance.

      The code I wrote is for indexing a stepper motor. The code the other person wrote was for correcting cumulative error that might occur with divisions that would need to be rounded off. The stepper motors offer a large range of index steps as compared to index plates. Here’s an example of what I’m talking about for anyone interested.

      Warning: VERY boring technical nerd stuff to follow! :D

      A common stepper motor uses 200 steps per rev. These motors can be 1/4 and 1/2 stepped offering many more indexing options ie: 400, 800 etc. Also some motors have reduction gearing built into them giving many more possiblities for dividing at acceptible resolutions for most horological needs.
      An example of a really inexpensive stepper motor with built in reduction gearing is the 28byj-48 …a very common motor often found in printers, scanners etc. It’s a very small low power motor with little torque but it’s reduction gearing of 1/16 makes it a surprisingly strong little engine. At only 32 steps the motor wouldn’t offer much variety of index steps but at the 1/16 reduction it now has 513 steps. So at that point any number from one to 256 can be divided into the 513 and those numbers that don’t evenly divide into 513 can be rounded off to the nearest whole number step. In addition stepper motors can be quarter and half stepped if desired giving a much higher number of steps to work with. So if the 28byj-48 is half stepped you will now have double the number -1026 – to work with improving resolution when dealing with numbers that won’t divide evenly into 1026. Problem was an accumulation of the remainder. That cumulative error could amount to a large number by the time the last tooth was cut. I was able to use zero as the reference point for each division which eliminated that error but then ran into the problem of repeatability when reversing and going back to a previous tooth. The code I found online corrected this backtracking problem allowing me to go back to any previously cut tooth, do whatever needs to be done with that tooth and pick up the indexing from that exact point with no error. It would then clear the entire program when a full 360 degrees was reached.

      Hope that makes sense. I may have messed up the explanation a bit but I think it kinda explains it.

      Adios for now,
      Bob

      #63794
      nic422
      Participant

        Wow, that’s an impressive and inventive way of doing things! So did you somehow hook this stepper motor up to the Head stock section of a Jewelers lathe to turn the headstock spindle bit by bit and do the cutting with a milling attachment on a compound slide rest? Do you have any pics of this set up?

        I also had another question. I have what is supposedly an American Watch Tool compound slide rest (although I can not find a logo on the unit) with similar base to a Marshall.

        However it is missing the foot.

        Do you know anywhere I can find a foot? If not, what kind of metal is advisable to be used to make one? metaldepot.com has different measurements I can buy but in many types of metals. Which do you recommend?

        #63795
        Bob Tascione
        Moderator

          Hi Nic,
          Never placed everything into it’s own enclosure for a permanent setup. Shelved the project about a year or so ago and figured I could jump back on it when I had a little time. Still waiting for that time. Will eventually get back to it and hopefully make it available online. We’ll see. It’s still mounted on a breadboard awaiting some tweaking and an enclosure. I did set it up on an 8mm lathe for testing though. Didn’t mount it behind the spindle for the test but put a three jaw chuck on the lathe which held a 6mm pin for mounting a small timing pulley with 6mm hole. Then ran a timing belt to a an equal diameter pulley which was attached to the motor. I held the motor in a small vise mounted to a board. It worked fine. One could actually mount the unit onto the lathe in this fashion (in front of the spindle) and cut a gear between centers if some means of support could be devised. When done it could be removed quickly from the lathe and put onto another lathe if desired. Anyway hope to finish it up someday.

          Just about any steel should work for you. You don’t need to worry much about strength since it’s just finger tightened. Something like 1018 or 12L14 would actually do fine. 12L14 being the easier to machine out of the two. No need to go to the hot rolled steels like 4140, 4150 etc. as warpage isn’t a concern at all. Those would be a little better though strength wise if you can get some cheap but not needed. Also higher carbon steels aren’t necessary unless you want to heat treat it for some reason. If you’re gonna be turning it with a hand graver on your watchmakers lathe then I would probably just grab a pices of the 12L14 (or try whatever you might have laying around the house). 12L14 has lead in it which makes it very easy to machine.

          Probably better choices out there but I don’t think it’s all that important for that application.

          Bob

          #63796
          nic422
          Participant

            I had gotten to a point where I’ve been wanting to post the update of rebuilding and re-accumulating parts and accessories for an all American lathe set up (as might of been used by early American watch makers), and then well life happened and I got busy with other stuff. Well, I thought before waiting any more I would update this thread as William was interested in seeing the set up when it was completed. Well, it’s not completed yet, but I have collected many parts and made a few to complete unfinished and broken ones like the handle on the turn for the mill, a custom wood base, a foot for a older era Marshall cross slide, and even made my own spring operated pinning set up for catching the index out of a cheap case back opening tool, and was able to find a way of attaching an index to the headstock collet holder (of course it is crude and needs re-thinking). Did a lot of refinishing and replacing of old rusted out and oxidized accessories. What’s left is a proper rigging of the countershafts, pulley set up, and gear cutters, etc. Any added thoughts?

            Some of the brands used are Peerless, Marshall, Hardinge, Snyder, Early Levin, Witcomb, Fleming, etc. However there is one modern Sherline chuck in the mix, and a Borel six jaw chuck.



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