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Thread: What does a 'Lathe Dog' do?

  1. #1
    Join Date
    Jan 2009
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    177

    Default What does a 'Lathe Dog' do?

    For the life of me I can't understand what it does. I've read countless threads, articles, looked at pictures, sketches, etc. and I can't figure out what it does differently than a 4 jaw chuck.

  2. #2
    Join Date
    Apr 2006
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    citrus heights, ca
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    A lathe dog is used to drive the work that is between centers. If You had a shaft between centers without the dog it would be like leaving the key out of a keyway.

    Steve

  3. #3
    Join Date
    Mar 2003
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    3,092

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    4-jaw?

    A lathe dog is a device used to drive a workpiece when turning between centers. And that means, instead of holding the shaft in a chuck, you have a center in both the headstock and tailstock.

    The headstock end is of course a "dead" center, while the tailstock can be either a live center or dead.

    The "dog" clamps to the shaft, and the leg of the dog engages a slot or hole in either a faceplate or "drive plate".

    In this photo, the machinist has clamped a center in the chuck, and the leg of the lathe dog is being driven by one of the chuck jaws.

    The technique predates chucks, and so tended to fall out of favor once 3-jaw and 4-jaws came on the scene. But turning between centers still has one solid benefit, in that it's very easy to remove the workpiece, for fitting, measuring or testing, and then put it back in the lathe very close to, if not spot-on, the original zero.

    Doc.
    Doc's Machine. (Probably not what you expect.)

  4. #4
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    Aug 2006
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    Beaverton, OR
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    Yep, like Doc said. Turning between centers is one of the most accurate ways to turn a part, especially things like a shaft that need to be flipped. Traditionally they are used with a dog drive plate as seen here on my monarch.


  5. #5
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    Yorkshire, Centre of the known Universe
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    Mine used to lay across the entrance to my workshop to stop visitors "Surprising" me while machining.

    Regards Ian.
    You might not like what I say,but that doesn't mean I'm wrong.

  6. #6
    Join Date
    May 2009
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    161

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    Quote Originally Posted by Circlip
    Mine used to lay across the entrance to my workshop to stop visitors "Surprising" me while machining.

    Regards Ian.
    Yessir, and if you're not careful he'll take a bite out of you wherever he is.

  7. #7
    Join Date
    Jan 2009
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    177

    Default

    Thanks for the replies, but I'm still confused how it differs from a chuck. I guess I can't figure out why I would use it versus a chuck.

  8. #8
    Join Date
    Apr 2007
    Location
    Fairport NY
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    Well...


    I take a shaft and I bore two holes in it. Then I put a center in the head of the lathe and in the tailstock.

    Now I suspend the part between these two parts and engage it with the dog. The dog locks onto the part and transfers the spin from the faceplate to the part.

    On paper, I can disengage the dog, take my part out and flip it around (end for end) and still have it keep the same location in the machine.

    You really can't do that with a jaw-chuck unless you are very very very good.

    Another advantage is you can turn long irregular parts that won't fit in the jaws.


    That said... Twice I've used this method in all the hours I've logged on the lathe. I'm more of a collet-chuck/turret-lathe/mass-production dood than a turner of epic parts.
    This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
    Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
    Plastic Operators Dot Com

  9. #9
    Join Date
    Jan 2009
    Location
    Southern WI
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    In today's machine shops, lathe dogs have NO place. Nobody cares about T.I.R about a given centerline. It simply is not cost effective, (They Think). We live in a world of Throw-away goods, where the Land-fills ARE a money making proposition. I just wonder what our children are going to do after we have used up Everything.
    If you want to make something precision, you use centers and a drive dog, when multiple set-ups are required or when repairing / reworking parts.

  10. #10
    Join Date
    May 2009
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    161

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    "I guess I can't figure out why I would use it versus a chuck. "

    If you aren't a well equipped HSM, say you wanted to turn taper between centers. You don't have a taper attachment. The dog drives the work from a center aligned with tailstock offset to required taper. Can't do that with a chuck.
    For fussier accuracy (TIR), dogs don't have jaw domination like three jaw chucks.

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