ST-20 Chuck Slippage
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  1. #1
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    Default ST-20 Chuck Slippage

    I know this is very broad/vague but I am just looking for advise on what people have run into before. We have slippage on certain materials when the thrust is not that great. Some bigger parts that require more thrust don't slip but these are. It is .960 diameter Dura Bar that is being hollow milled.

    Oil level is good, chuck is lubed. The holding method is Warner Swasey Collet pads fir to a 3 jaw. Pressure readings are good. Before I take chuck off and clean everything I just wanted some input as to what other people have found when things start slipping.

    Thank you for the help.

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    so are you saying your having clamping issues. or rotary positioning issues? I'm guessing clamping pressure issues. is there a possibility that your right at your minimal clamping diameter? And may have to move the jaws in 1 position? I have seen this be a issue, especially in shops that dont frequently clean there chucks.

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    Thanks for the reply. We are having clamping issues. The bar is sliding into the machine in Z. The indicator, you know the little marks on the chuck, has the chuck throw in the middle.

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    Sounds like a dull tool putting excess pressure on the part.

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    Are you using .960 dia collet pads? If not, that's part of your problem. Try boring a set of soft jaws to .960.

    How long are the bars? Are you using a spindle liner? How fast are you spinning these?
    I've noticed longer bars seem to have mass behind them and resist pushback, but there is a sweet spot where it starts to push in. Slower feedrate, slower RPM, fresh inserts.

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    Thanks All for the replies. Red James inserts are brand new and the Z thrust is low, 25%.

    Booze the pads are a little big .968 and am using a liner. The big issue is we run this all the time with out problem.

    The fix was tear everything down, clean it all and start over. There was no dirt or chips in the chuck but all is working now. I guess it just wanted some tender loving care.

    Thanks again for trying to help.

  7. #7
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    glad you got it fixed.

    i've seen clamping problems when the chuck needed a little bit of grease.

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    The mark on the master jaw should be toward the bottom of the stroke. You will get the most clamping pressure in the last 25 percent of the stroke.

  9. #9
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    FrankieB,

    That's interesting. I'll keep that in mind. We have bored a set of jaws to accept W&S collet pads. Most of the time we are near the end of the stoke and wiil strive for that from now on.

    Thanks.


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