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Thread: Repairing Pot Metal or White metal

  1. #1
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    Repairing Pot Metal or White metal

    I have an old Dayton belt/disc sander. One of the trunions is broken and a replacement costs $135 with shipping. I did a web search and some companies now sell a brazing type rod they claim works for Pot metal. I hate to shell out $135 bucks for such a simple part. Has anyone here had experience with repaired Pot metal?

  2. #2
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    Have you tried JB Weld? A friend used it to repair a cracked crank case on a harley and it worked great.
    Those who sense the winds of change should build windmills, not windbreaks.

    Dave Wilson

  3. #3
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    Joe,

    Your trunnion is probably cast iron which can be braze welded. Pot metal is an old term that means cast aluminum to me, very low quality stuff...anything they throw into the pot kind of thing.

    Brazing cast iron isn't easy. You need the proper flux and heat source, preferably an oxy aceteline tourch to get the proper heat. I know there are other less expensive means. If you are unfamillier with brazing take your trunnion to a local welding shop, they have the expertise and materials to do the job right. Properly welded it will last for the life of the tool, improperly welded and it will break again when you reinstall the part.

    Davids suggestion about JB Weld adhesive is worth considering.

  4. #4
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    If it is cast iron it can probably be welded, if its a small piece like you say preheatings probably isn't required, and a welding shop should be able to do it in a short time.

    Like said, brazing might be something you could try, but poor quaility cast iron is not nice to work with, only somewhat better than pot metal (like older car door handles and such).

    I think if I was a bit uncertain about my welding/brazing ability, I'd use the JB Weld, clean and degrease the piece and make sure you give the JB enough time to completely set up.
    You'd probably be supprised at how strong that stuff can be.

    Al

  5. #5
    Joe:
    I agree with Keith in that if you are not familiar with brazing cast iron take it to someone that is. I've watched some of the old Boilermakers (RR) do this and it was a slow process.

    They'd first heat the metal using charcoal for about 8 hours then do their brazing being careful not to over heat the component the when they were finished they would cover the metal with (at that time) an asbestos sheet and let the charcoal burn itself out and cool the metal to room temperature. At that point they'd surface grind the braze and paint the component.

    This was done on large railroad car truck frames and I never saw one crack again when this procedure was used. With a small object as you described a high temperature heat lamp may suffice in place of the charcoal. If the metal is cooled too quickly it will crystalize and crack.

    Roger

  6. #6
    It is most likely a cast aluminum in which case JB Weld might be your best option. Aluminum can be welded (not sure about cast) but I've never had any success doing it. It's easy to get to a melting point but it just doesn't want to bond. If you try to weld be careful of your temps as aluminum melts in the area of 1000-1100 degrees. You can get there pretty quick.

  7. #7
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    Joe,
    I had a bandsaw with a broken trunnion. (pre WWII with no replacements available) I used JB weld and it is still working fine 5 years later.

    Wes

  8. #8
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    The trunion is definitely not cast iron, but it may be cast aluminum. It's fairly thick, maybe 3/16", but where the break the repair will be under heavy tension. I'm skeptical that epoxy will work on a glue surface only 3/16" wide under tension. I'm going to call some shops today to see if they can weld.

    Anyone know a test to determine if it's aluminum or Pot metal?...joe

  9. #9
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    I would not trust Jb weld on a part like that. Take it to a welding shop and p[ay the 3o bucks and let them fix it. That way it is done right and there will be no warping to worry about.

  10. #10
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    I took the part to a couple of shops today.
    1) It is definitely Pot metal which means it's cast zinc.
    2) There are brazing rods available for Pot metal, but the shops had tried them with poor outcomes. Neither shop would even try.
    3) I could buy the rods myself, but with shipping the minimum was about $60.

    I ended up ordering the replacement part which ended up costing $148 with shipping and tax

  11. #11
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    Quote Originally Posted by Keith Outten
    Joe,

    Your trunnion is probably cast iron which can be braze welded. Pot metal is an old term that means cast aluminum to me, very low quality stuff...anything they throw into the pot kind of thing.

    Brazing cast iron isn't easy. You need the proper flux and heat source, preferably an oxy aceteline tourch to get the proper heat. I know there are other less expensive means. If you are unfamillier with brazing take your trunnion to a local welding shop, they have the expertise and materials to do the job right. Properly welded it will last for the life of the tool, improperly welded and it will break again when you reinstall the part.

    Davids suggestion about JB Weld adhesive is worth considering.
    Pot metal is zinc or a zinc alloy. About as durable pudding.

  12. #12
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    Quote Originally Posted by Frank Fusco
    Pot metal is zinc or a zinc alloy. About as durable pudding.
    Yea, I'm amazed that a generally well constructed tool uses cheap parts in some high stress areas. And then they have the gall to charge $121 for a small non-precision part on a machine that lists for $750...joe

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