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Thread: heat shrinking a blind bearing race -- good idea?

  1. #1
    Join Date
    Mar 2001
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    Question heat shrinking a blind bearing race -- good idea?

    I'm rebuilding a vintage steering idler unit that has a shaft supported by two tapered roller bearings. The cone of one of the bearings shows some pitting, probably due to some moisture getting into the unit, and then sitting unused for 35 years with no motion to move the grease around. I've ordered a replacement bearing, but can't figure out how to remove the pitted cone.

    Here's the setup: the idler unit is cast iron in the shape of a tube, with external "ears" for mounting and steering stops. The central cavity is rough cast, with an inner diameter that is very slightly larger than the inner diameter of the cone (about 1 3/16"). The cone is pressed into a recess bored in the casting. If I run a finger down the central hole, I can just feel the transition between the ID of the cone and the ID of the casting, but there isn't enough of a step to grab the cone with a puller or to hammer it with a punch.

    I've read that bearing races can be removed by welding a bead on the ID of the race. See: https://www.hemmings.com/blog/2009/0...bearing-races/ and https://app.aws.org/forum/topic_show.pl?tid=9540

    I think the idea is that since the race is constrained on the outside, when heated until plastic the thermal expansion forces the metal toward the central hole. Then, when it cools, it shrinks uniformly, including the OD. The filler metal, if used, has nothing to do with it -- it's the heating, upsetting, and cooling that does the trick. So oxy-acetylene, carbon arc, or TIG with no filler should also work. Quenching with water whould probably help, too.

    Does anyone have experience using this method? It would have to shrink the cone enough so it pretty much falls out of the casting on its own. I hesitate to try this method because if it failed, I would have buggered the bearing without getting it out, and since the idler assembly is NLA, that would be a big problem.

    I suppose an alternate method would be to machine a disc that fits inside the cone, and weld it to the cone. Then, if the shrinking action doesn't do the trick by itself, the disc would provide a surface to push against with a hydraulic press.

    Comments? Suggestions?

  2. #2
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    Having removed many, many bearings over the years I can tell you that just heating a bearing won't do the
    job. Any time you deposit a bead of weld it will tend to shrink the parent metal to some extent. It isn't
    just the heat but the shrinkage of the weld that makes this method work so well. The race actually shrinks to
    a size that is smaller than original and just drops out.....literally. Heat by itself will loosen a stuck bearing but
    it won't significantly shrink one...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

  3. #3
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    Yes, it works and its my preferred method even if its not a blind hole.

    I prefer TIG torch for heating, no need to use filler, just melt a straight "bead" or zic-zac pattern around the bearing race and it falls off. Filler helps to get some extra shrinking but I never use it with TIG.
    I use TIG torch even for inner bearing races stuck to shaft but there you have to be quick and pull the race out while its still hot.

  4. #4

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    Bend up a welding rod and into it, works like a charm, it's about the only way that I know of to get it out without buggering anything else, done hundreds of 'em that way.

  5. #5
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    LKeithR, Good to know that the welding method works and that the race just drops out. What I had in mind isn't just heating, but actually running a puddle around the race and letting it freeze. If molten filler metal has a shrinking effect when it freezes, then molten base metal should, too. Anyway, I don't have a problem using the tried and true welding method, I'm just trying to understand how it works. Do you weld all the way around the race, or are some stitch welds enough?

  6. #6
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    Greenie, Not sure I understand what you mean by "bend up a welding rod and into it." Can you explain?

  7. #7
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    my guess is you would only need to weld a puddle on the order of 60-120 degrees of the bearing for a typical fit where a bearing is .001" diameter larger than the bore. add another .001" for corrosion stresses so you only need the bearing to shrink .002" in diameter and it will fall out. this is practically nothing when compared to normal distortion when welding.

    anyhow the instant you heat metal up and its constrained in a press fit bore, it expands, yields, then cools off and shrinks. adding base metal to your heat source only increases the shrinkage.

  8. #8

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    If it's down deep, then give the end of the welding rod a bit of a bend, that way the end of the rod is squarer to the bearing surface, just makes it easier to do the weld.
    If you got the rod straight down the hole, then the end of the rod can slip of the bearing surface, not good.
    If you can, make the weld the whole way around the bearing surface, it just drops out when cooled and you turn it upside down and shake it.
    Last edited by greenie; 09-13-2019 at 04:05 AM.

  9. #9
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    Weld them out all the time,best if you weld all the way round.Yes the deposited metal contracts as it cools,but also the heat expands the housing some at the same time,
    I have and often do find a flat washer that fits down almost through the bearing race and weld it in.It has the same effect,but also gives you something to drive against if the weld doesn't give you enough shrink.
    I just need one more tool,just one!

  10. #10
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    Here is an example where I used the method to remove a race from the clutch of my old horizontal mill. I certainly did not want to beat on that unobtainable piece. Someone on this forum showed me the method if I recall. You can see my bead about 90 degrees around. As stated above, the race dropped right out.




    Tom
    Last edited by flathead4; 09-13-2019 at 05:40 AM.

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