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Thread: What's the best material and fit for an oil-less air compressor piston seal?

  1. #1

    Default What's the best material and fit for an oil-less air compressor piston seal?

    I've got a Task Force air compressor which wasn't making pressure. The cylinder was scored and the seal on the piston was folded down and split on one side.

    I've turned and polished the cylinder bore. Now I need to make a new seal for the piston, but I'm not sure what to make it from. The piston is about 2" in diameter. It doesn't have a piston pin, so it rocks as it goes up and down in the bore. The seal is clamped to the top of the piston with an aluminum disc. This is the old seal:



    It appears to be some sort of plastic, but there are no markings on it.

    I've got some UHMWPE and some Delrin. Would either of those work for the seal?

    Also, what kind of fit should I have between the piston and the bore?

    I've tried to find a source for parts, but Lowes no longer carries TF compressors. The place they recommended for parts only carries parts for items still sold in the store.
    Last edited by winchman; 11-30-2010 at 05:34 PM.

  2. #2
    Join Date
    Feb 2009
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    141

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    UHMW is used in some pneumatic and hydraulic seals as it has fair resistance to oil. But have you checked with seal manufacturers/hydraulic supply shops for the seal? Forget what it came from, you just need the specs on the seal. Looks like a typical design, and seals aren't that expensive, what with cylinders and pumps being rebuilt all the time. Just google "hydraulic seals" and you'll find a ton of sites with info to peruse.

  3. #3
    Join Date
    Feb 2010
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    Spokane
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    Any Delrin (acetal) that I am familiar with would be much too rigid for this application.

    The seal needs to have a thin flexible edge to seal in the bore as the piston rocks to follow the crank pin.

    UHMW might work if the cycle was limited to one tank fill up, but I don't think it would tolerate the heat for any kind of continuous use.

    I think some kind of teflon would be the best.

    Dave

  4. #4
    Join Date
    Jan 2003
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    Temple, Tx
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    Repair kits for that type of compressor are very cheap.

  5. #5

    Default

    Where do you get them? I've searched online for about an hour. The closest thing I could find was a link to the Sears parts site that says the item is not economical to repair:
    http://www.searspartsdirect.com/part...P0506125/00001

    Maybe that's why it was in the dumpster.
    Last edited by winchman; 12-01-2010 at 02:15 AM.

  6. #6
    Join Date
    Mar 2005
    Location
    Palmer Alaska
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    After listening to my neighbors similar compressor from over 600 ft away, without my hearing aids in..

    The cheapest repair is to chuck it right back where it came from. Hearing aids cost BIG money...

    Worthless 40 hour life, NASTY LOUD machines...

    Beancounters over brains.. Buyers the same...

    My dad was a commercial painter for 30+ years. Told me long before those cheap ones came out, to get a cast iron pump (pref with pressure oiling) with seperate belt driven motor.
    Last edited by Bguns; 12-01-2010 at 06:28 AM.

  7. #7
    Join Date
    Aug 2009
    Location
    Canada, Bc
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    Bguns is 100% correct
    Toss that cylinder out, Buy a nice oil lubracated *LOW RPM* piston compressor. $200~ or so, And change the oil once a year, insted of the seals once a month!

    My low rpm 2hp piston compressor is quite enough to talk over, What a consept!
    My higher RPM 5hp compressor.. Maybe you can shout over it. But then, its a much bigger unit.

    Every 1hp oilless compressor iv heard is even louder then my 5hp compressor.

  8. #8
    Join Date
    Sep 2010
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    630

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    on the other hand, they dont mind falling over......being sat at an angle or even being pushed over while running....... all real risks out of the shop....

  9. #9
    Join Date
    Feb 2005
    Posts
    325

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    mcmaster carr has cup seals. If it is very old it may be leather.
    re
    Herm Williams

  10. #10
    Join Date
    Jan 2003
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    Temple, Tx
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    Sears sold kits in the past. If you look up Porter Cable, or others, you will find kits for them. Sears seems to have copped out. I am not sure who makes the Sears compressors, but maybe they still sell them.

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