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3 jaw chuck run out

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  • J Tiers
    Originally posted by Black_Moons
    Maybe its not his jaws that are out but just the mounting to the D6-1backplate that isent aligned as theres no register for it to the chuck itself?
    Easy to check by checking runout on the chuck body. Any decent chuck company will not tolerate much runout of the chuck body vs true axis, it should be in the tenths.

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  • MichaelP

    You mean this model allows a self centering (vs. independent) operation with a 0.001" work side runout?
    Last edited by MichaelP; 11-06-2009, 11:17 AM.

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  • gwilson
    My favorite chuck is the 4 jaw Bison UNIVERSAL chuck. I must have bought 8 of them over the years for a succession of lathes at work and at home.

    They all ran only .001" out. I mounted them all on backplates myself. My Bison at home is less than .001" out.

    And they weren't too expensive a chuck(at least before their price increases.)

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  • Black_Moons
    Maybe its not his jaws that are out but just the mounting to the D6-1backplate that isent aligned as theres no register for it to the chuck itself?

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  • EVguru
    Check if the chuck has a mark by one of the key holes. This is the 'master' and the one that would have been used when the jaws were originally ground. If you decide to grind your jaws then mark one key hole to use.

    If you ever need to hold something really tight, you should really use an independant 4 jaw, but using all three key holes will enable you to grip tighter without straining the scroll.

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  • polepenhollow
    I have a lathe with an L00 spindle snout.
    My chuck had about .015 runout. I took off the chuck, turned the mounting spigot on the backplate undersize by .010.
    I held a .625 dia dowel in the chuck jaws and indicated in the dowel/chuck combo to swing "0" on the reduced dia backplate.
    Tighten screws and you are in business.
    If it goes out in the future or it is radically different at a different dia, re-indicate the part and retighten the chuck to the backplate.
    Works great.

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  • darryl
    This just my own experience, but I've found that if you mix the jaws up, they won't even come close to centering. I'm talking about 100 thou or more of offset- if a mounted workpiece has less than 10 thou of runout the jaws are most likely in the right slots.

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  • dm1try
    i recently got a NOS 80mm (3") polish-made BIAL CT-80A chuck. the certificate says:
    body runout: 0.01mm (0.0004")
    radial runout of a mandrel in inside jaws: 0.01mm (0.0004")
    radial runout of a ring in inside jaws outer steps: 0.012mm (0.0005")
    radial runout of a ring in outside jaws: 0.012mm (0.0005")
    face runout of a ring: 0.006mm (0.00024")
    haven't verified that myself yet, though

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  • gnm109
    Guest replied
    Originally posted by motorcyclemac
    I clamp a piece of steel round stock with a hole in it.... in the back of the jaws and then use a tool post grinder to true up the jaws. Mark the steel so it aligns with the #1 jaw (or any jaw for that matter as long as you mark it). I then clamp the same piece of steel with the hole in the middle in the newly trued up faces (aligning it with the same jaw) and clean up the back end portion where the piece was clamped to start.

    Once done...make sure to dissassemble the chuck and clean it very well. The grinding swarf will chew the chuck to pieces if left inside. Oil it well and then check for true.

    That's what I do. I had the jaws of my 6" 3 jaw Enco D1-4 wear loose on the outer ends after some 15 years. I ground it as above and got it very close. I don't remember the number but now the chuck holds nicely.

    On a three jaw, some runout is to be expected and really isn't a problem unless you want to machine something round and remove it and replace it. That can cause a problem, but I'm sure everyone here already nows that.

    If the jaws aren't loose and the chuck is nice and clean, you can get them quite close with a regrind. I also made a holder for a pneumatic die grinder that I did the job with.

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  • loose nut
    Even if it was within 1 or 2 thou it wouldn't hold that accuracy for very long anyway, 3 jaws aren't meant to be really accurate at least the ones we can afford.

    .003 good
    .020 bad
    .007 not terrible.

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  • philbur
    If the chuck is mounted on a backplate remove the chuck from the backplate open the mounting holes on the backplate by 1 mm. Reduce the chuck register diameter by 1 mm. Put the chuck back onto the backplate and your chuck is now adjustable for concentricity.

    A common or garden three jaw chuck is a bench vice designed for mounting on a spindle.


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  • oldtiffie

    Buy/get some jaws for that chuck that "soft jaws" can be fixed/mounted to.

    Get/buy/make some soft jaws.

    Close the soft jaws onto any bit of round stock that suits and bore and/or face the soft jaws to suit the job in hand.

    The machined surfaces in the soft jaws will be as accurate and an as "true" to your lathe as is likely to be required. Should be "true" to within "half a thou" - or better.

    Best result for least time, effort, "drama" and buggerising around.

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  • J Tiers
    Originally posted by Mcgyver
    just use it.

    I've never understood this 3 jaw runout concern in the sense that even the good ones are going to be 2-3 thou out. For what class of work is 3 ok but 7 not? imo, the three jaw is either for very rough work where it doesn't matter whether its 3 or 7 OR for work where everything is turned at one setting (thus ensuring perfect concentricity)

    when you need concentricity to a work holding surface or repeatability, use a collet, 4 jaw or centres....not a cheap or expensive 3 jaw
    it matters because it is annoying.

    it matters if you would like to get all the work "inside" the piece you start with, and that's close to net size.

    Did I mention that it is annoying?

    Pretty much like crosslide slop. Yes, it doesn't really matter in most situations, but it is annoying, a source of calculation errors, etc.

    And it's annoying, of course.

    Go ahead and grind.

    But, turn some plugs to fit the top jaw holes, and close the jaws on a ring grabbed by the plugs. (for thos having solid jaws, drill holes with a 1/8 masonry bit or other carbide in highest jaws)

    Closing on a ring at the heel may not matter in this particular case, but if the jaws are worn, it doesn't load them the way they get used, and will leave the jaws bellmouthed after grinding. (method originated with Rich Carlstedt)
    Last edited by J Tiers; 11-05-2009, 08:57 AM.

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  • wierdscience
    Clamp with the master and grind/bore the jaws true.After that check a few diameters for runout.If there isn't any it's cured.If it still has runout,especially inconsistent runout then there is no fixing it.

    I will go along with a fourjaw being better,but only so far as the fourjaw not being bell mouthed.They do wear out too.

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  • oldtiffie
    Its new after all.

    This is the OP.

    Originally posted by shawnspeed
    all righty now , I know I will get a little critisism out of this , but here goes....I purcahsed a 3 jaw Wholesale Tool(import, I should know better, but can't afford a buck /cushman right now) D1-6 chuck on clearance for 100 bucks as is ....I figured it got returned because of exessive runout....and I was right ...6-7 thou...checked with several different diamiters always the same jaw high /low & one in between, the same amount. I then put a 5 thou shim on the low jaw , and it got everyting under 2 thou , which is totaly acceptable for most of the stuff I do on a regular basis. Now how do I fix it permanently/correctly????the only thing I can come up with is using a tool post grinder to true up the I correct in my thinking , or is there another way????Thanks in advance , Shawn

    There is no need here, so far as I know - or care - that requires you or anyone else to get or have the approval of anybody (else) for anything that you buy or do or where anything is sourced from.

    It follows then that there is no need to explain or apologise either.

    From what I can see, that should be a good chuck - period.

    The chuck should not need regrinding as it is - for all intents and purposes - new.

    Here are the specs for new chucks - Chinese - so check them out.

    The "acceptable" figures are in millimeters - 0.001" is about 0.025mm.

    It seems that the chuck the OP has is not too bad after all.

    I agree with Mcgyver's advice and sentiments - just accept is for what it is - pretty good really - and get on and use it "as is".

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