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Getting the workpiece straight in the chuck.

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by Tailormade, May 2, 2017.

  1. Tailormade

    Tailormade United States Iron Registered Member

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    This was my result when I had my gallery failure that sparked the question.
    The pic didn't show it well,but the variance is between .064 and .159

    I'm going to try the tapping method and see how that goes.[​IMG]
     
  2. Tailormade

    Tailormade United States Iron Registered Member

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    I must be doing something wrong in this method. Does not appear any better. This is the other end of the same bar.

    158 on the high side, 89 on the low side.[​IMG]

    Sent from my VS995 using Tapatalk
     
  3. umahunter

    umahunter United States Active User Active Member

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    Search a video by Joe pieczynski on youtube called "getting your parts to run true in a non adjustable chuck you must watch this" I would link it but it doesn't work on my phone for some reason he has some really good videos :)
     
    royesses likes this.
  4. royesses

    royesses United States H-M Supporter - Premium Content H-M Supporter-Premium

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    here is the video:


    Roy
     
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  5. mikey

    mikey Active User H-M Supporter-Premium

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    Tailormade, are you still trying to sort out how to center drill a 15-20" work piece at the far end without a steady rest? Not to be facetious but the answer is pretty simple - use a steady rest, center drill the end and bring a live center into contact with the drilled center before trying to turn the end. You have a 15-20" long lever arm acting on chuck jaws that are what, maybe 1.5" deep and keeping it solid and centered at the far end is just not going to happen without a steady rest.

    If I recall correctly, you have a steady rest with gnarled up arms, right? Sounds like an opportune time to fix that situation.
     
  6. Tailormade

    Tailormade United States Iron Registered Member

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    Not right now. I just happened to have a piece that long and was going to use it to try different operations on it. I am new to this old lathe, and new to lathe's in general, so I just picked a piece from the bar stock I have that was shorter than the previous simple project I'd done with a friend and tried to chuck it up and do stuff.

    Since then I've just been trying smaller shorter pieces to try stuff out. My lathe didn't come with any tooling aside from a carbide insert boring bar with no inserts, so I've been trying to figure out making hss cutters and have them not be crap.

    That is my plan for that kind of work going forward.

    One thing I have been confuzzled by is how does one get the workpiece correct in the steady rest? Not that I can't manage it, but with three (well two) points on the rest to worry about, plus the chuck itself it seems like there is probably a method that works well, and then the way I'd do it.

    Yes, I've been looking into how they should look, so I grind them right. I'd also been looking at those retrofit replacement arms with bearings and wondering if I should just get those.

    Either way I need to learn how to use a steady rest properly for those longer pieces.
     
  7. 4ssss

    4ssss United States Active Member Active Member

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    That video just goes to show that even though someone owns a business doesn't always mean he knows what he's doing. Want a part to run concentric in a 3 jaw? Do yourself a favor and buy a Buck Chuck and follow the above instructions.
     
  8. mikey

    mikey Active User H-M Supporter-Premium

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    If you are getting those results from a short piece held just by the chuck then you may have some issues with the chuck or possibly from excessive cutting forces from your tool that results in deflection or your spindle is really worn. Try mounting a short piece, maybe 1-2" sticking out of the chuck and try again. If you still have that much error then you have some issues to work out. I suggest something soft, like aluminum or 12L14 for this test.

    For use with a 3 jaw, lock the work into the chuck and bring your steady rest as close to the chuck as you can. Bring the two lower arms up so that they juuust, touch and lock them down. Then lower the top arm down so it just touches. Theoretically, the work is aligned fairly well by the chuck and you have fairly closely duplicated that alignment with the steady rest. Now unlock the steady rest and move it toward the end of the work piece and lock it down. You have now transferred the alignment of the work piece to what it has at the chuck end. Oil the work and turn the lathe on, then drill your center hole with a center drill. You can now remove the steady rest and engage a live center into the hole you just drilled and proceed to turn your work piece.

    When using a 4 jaw independent chuck, you can get things much more precisely aligned. You dial in the work at the chuck and then dial in each arm of the steady rest that is positioned near the end of the work. There are other ways to do it. Joe Pi (previously linked video) has a neat way to do it; check his videos.

    Each arm of the steady rest should be the same with regard to the contact points. They don't have to be precisely the same but at least close. The ball bearing thing is a good idea if you can incorporate it but not necessary; plain brass arms work well, too.

    What lathe do you have? What kind of turning tools are you using? What is the material you're cutting? The more you give us, the more we can help.
     
    brino likes this.

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