Lathe crash chuck
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  1. #1
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    Default Lathe crash chuck

    Had a nice crash today on my lathe...stupid mistake that will probably ain't cheap to fix.
    Was doing too much stuff at the same and made an error in the cam program.
    The tool went too fast into the z axis causing the material to be thrown out of the chuck.

    Besides a broken insert and damaged toolholder. The chuck does have runout...
    I removed it and check everything but one jaw seems to be very snug in its slide. Had to use a hammer to get it out.
    First I was thinking the jaw was damaged/bent but that wasn't the case, because the jaw works fine in the 2 other slides.
    And the 2 other jaws don't work in the damaged slide.

    I also removed the internals of the chuck and cleaned everything. But didn't solved the issue.
    Can I throw this chuck in the bin...? Or is there a way to fix it.


  2. #2
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    You're using a scroll chuck on a cnc lathe? Are you unable to use a hydraulic chuck?

  3. #3
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    It's from a Emco lathe
    They where available back in the day without and with hydraulic chuck.

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  5. #4
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    Quote Originally Posted by tcncj View Post
    Had a nice crash today on my lathe...stupid mistake that will probably ain't cheap to fix.
    Was doing too much stuff at the same and made an error in the cam program.
    The tool went too fast into the z axis causing the material to be thrown out of the chuck.

    Besides a broken insert and damaged toolholder. The chuck does have runout...
    I removed it and check everything but one jaw seems to be very snug in its slide. Had to use a hammer to get it out.
    First I was thinking the jaw was damaged/bent but that wasn't the case, because the jaw works fine in the 2 other slides.
    And the 2 other jaws don't work in the damaged slide.

    I also removed the internals of the chuck and cleaned everything. But didn't solved the issue.
    Can I throw this chuck in the bin...? Or is there a way to fix it.

    Sell it on eBay. Describe it well. Some hobbyist will try to fix it. He has time to play. I don't think you do.

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    I don't have time for it indeed. But maybe it was an easy fix.
    But strange that the jaw isn't damaged but the big chunk of steel?/cast iron? is.

    So will buy a new one. Bison (polish company) makes ok chucks right?
    Don't want to spend a huge amount of money on this lathe that will be replaced soon anyway.

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    Quote Originally Posted by steve-l View Post
    Sell it on eBay. Describe it well. Some hobbyist will try to fix it. He has time to play. I don't think you do.
    Couldn't agree more. I ASSume that you have got your money worth out of the chuck already... spoil yourself and buy a new one.

    Hell, If you can sell it as Steve said with fully describing it then at least you will be able to buy lunch for yourself on the day it arrives.

  9. #7
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    Quote Originally Posted by tcncj View Post
    .....Besides a broken insert and damaged toolholder. The chuck does have runout...
    I removed it and check everything but one jaw seems to be very snug in its slide. Had to use a hammer to get it out.
    First I was thinking the jaw was damaged/bent but that wasn't the case, because the jaw works fine in the 2 other slides. And the 2 other jaws don't work in the damaged slide.
    Every time I've worked on a crashed lathe where the chuck was damaged, there were other elements of the machine damaged or whacked out of alignment too. A thorough inspection and is warranted.

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  11. #8
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    The chuck was mounted directly to the spindle.
    Spindle is A2-5.
    Is there also a DIN number for it? Or is A2-5 completely different?
    Because a quick search trough some shops only mention DIN6350 mounting.

    edit

    I think DIN 55026 is a2-5?

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    yanked out a 4" dia x 12" long acme thd bronze nut from my 10" bison chuck. not sucked out, big crash mode. took apart, careful clean and deburr, my prev .001 runout was now .004. took it apart, cleaned again, same .004. and not repeatable, but about .004 the worst. boring soft jaws, it would be .002 or so. $250? or so chuck, accepted it for what it now was. still could be used for more precise stuff, put 2nd end ops in and indicate prev machined surfs carefully, it would hold whatever you took the time to knock it into with a brass bar on the jaws and part. did pay to do the indicating after roughing and before finish. no longer good for 2nd end precision with speed without say a pot fixture. most of the work on my 17" lathe had enuf time built in to cycle time you could spend that time with the brass knocker and an indicator. more you do it the faster you get.

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    I would be hesitant to bin it so quick. Check all the contact surfaces for burrs run an indicator on it parallel/flat/perpendicular. Feel the action of the scroll. If the one jaw fits where the other two go but the other two don’t fit where the one goes then I’d check the jaw and that section of the chuck. If that all shakes out then check the point of connection to the spindle.

  14. #11
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    Take a skim cut and hard turn the hard jaws. You'll probably have to re-cut all your soft jaws too.

  15. #12
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    The jaws are fine
    It's the guide in the chuck for one jaw that has been damaged.
    There are no burs. It looks like the guide for the jaw is smaller because of the crash.

    But I bought a new chuck and adapter plate. Should be ok now.
    Spindle is luckily not damaged.


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