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VFD on a Clausing 4800 for low speeds

Discussion in 'CLAUSING-COLCHESTER & BANTAM' started by Enderw88, Jul 16, 2017.

  1. Enderw88

    Enderw88 United States Iron Registered Member

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    Yesterday I busted a tooth off of the bull gear. Unfortunately it was right next to a tooth that was missing when I bought the lathe. From what I can tell I am more likely to win the lottery than find a good condition bull gear. I read up on some methods of repairing it but none of them really inspired me with confidence.

    I really don't like the idea of trying to thread things without the back gear. I am considering adding a VFD/3-phase motor to use in place of the back gear. I understand about being down on power at lower speeds, but on the back gear I am usually just threading which should require lots of grunt. Are there any other drawback anyone can think of? Or, am I wrong about not being able to find a bull gear?
     
  2. wa5cab

    wa5cab Downloads Moderator Staff Member H-M Supporter-Premium

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    You should at least call Clausing and find out whether or not they still have the gear and if so for how much. Personally, in a case like this I'd bite the bullet and ignore how much it cost. If you put a VFD on the machine (which might be worth doing for other reasons) about the slowest that you can run it is 1/3 the standard motor RPM which for 3.phase will usually be 1800. Below that, the motor will rapidly overheat. At 600 RPM, your slowest RPM will be 64, twice the slowest RPM in back gear.

    As far as finding a used one, I don't know the odds, but not as good as it would be if the machine were an Atlas, because not as many of them were made.
     
  3. machPete99

    machPete99 United States Steel Registered Member

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    Concur with Enderw88. I have 5914 which I converted to VFD (no countershaft) but still use the back gear a lot.
     
    Last edited by a moderator: Jul 17, 2017
  4. RWL

    RWL United States Active User Active Member

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    I cut my first gears last winter to help out a neighbor whose Rockwell lathe had a couple of broken change gears. It wasn't all that hard. If you have a torch capable of brazing, build up some bronze where the tooth broke off and cut a new tooth. Technically the tooth cutting could be done on your lathe, and it wouldn't take a dividing head, just some way to index the teeth on the existing bull gear. The gear cutter would be on an arbor in the lathe. The bull gear would be mounted horizontally on the compound rest and fed in by the cross slide. You would need a series of spacers of increasing thickness to lay the bull gear on to raise it with regard to the gear tooth cutter. It would be a lot easier if you have a friend with a mill and a dividing head or a friend with a shaper. Of course, the easiest route is to find a used bull gear with all its teeth and buy that if it's reasonably priced.
     
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  5. machPete99

    machPete99 United States Steel Registered Member

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    There are some youtube videos on different tooth cutting techniques. Before brazing you will want to grind out a bit of a pocket, so the new tooth has some root material to help stabilize it.
     
  6. markba633csi

    markba633csi United States Active Member Active Member

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    You could also try Al Meekins at www.gearsmade.com and see what a new gear would cost. Or maybe adapt an off-the-shelf gear from Boston or Martin?
    Mark S.
     
  7. Enderw88

    Enderw88 United States Iron Registered Member

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    Update here:
    I called Clausing and they no long have any bull gears but they did send me a drawing, so at least I had a definition of what the gear is: 78 Tooth 16 Pitch 14.5 degree PA.

    I have found a stock gear from Linn Gear that I can get a hold of. I am going to adapt it to the Clausing using an aluminum gear carrier I am aching now. I will post a new thread when I am finished with the results, good or bad.
     
  8. markba633csi

    markba633csi United States Active Member Active Member

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    Cool, good ol' yankee ingenuity
    Me
     
  9. RWL

    RWL United States Active User Active Member

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    I've got the set of gear cutters for 16P gears. If your plan doesn't work out let me know and I'll cut new teeth for you on your gear for the cost of shipping/and any out of pocket expenses. I haven't looked at the bull gear of a 4800 since I sold my 4800 several years ago, but my recollection is that it had a pin that you had to pull out to put it in back gear. Making a hub with that part of it would be a bit of a pain. If it were just making a bushing to change the hub size it would be easy.
     
  10. Enderw88

    Enderw88 United States Iron Registered Member

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    Those protrusions that support the pin are annoying. But I think I have a solution. There is enough material in the gear to make that hub. The real question in my mind right now is balancing the thing. I need to see the back side of the original bull gear to see where the material is removed. I attached a preliminary drawing of the hub I am making. It will require boring the Linn gear out to fit.
     

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