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Oversized bronze bushings.

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  • Oversized bronze bushings.

    I recently purchased some " Bronze " bushings of various sizes from Princess Auto ( Harbor fright's Canadian cousin). They are all about 5 thous over nominal outside dimensions, and certainly will not press in simply using my bench vise. I have used them by boring out the housings a couple of thous more to give my usual fit ( One thous plus one thou for each complete inch of bore over one inch )). I am used to using bronze bushings, or oilite bushings bought over the counter from proper engineers suppliers that are just about a thous or so above nominal size and can be pressed into nominal sized holes with a light press fit which shrinks the inner bore to nominal size to usually give a running fit without reaming or boring. I wonder, are there industry standards, do individual manufacturers have their own, or was simply unlucky in getting some made on a Monday or Friday? Yes I know you SHOULD not ream oilite bushings, but I bet most of us have done so! Regards David Powell.

  • #2
    http://www.mmto.org/dclark/Reports/Encoder%20Upgrade/fittolerences%20%5BRead-Only%5D.pdf



    Check out the above link.
    Engineers live and die over FITS.
    Remember female is uppercase, male is lowercase.

    -Doozer
    DZER

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    • #3
      Mr. Powell
      Yes, there are "standards", and you were simply unlucky that what was procured did not fall within your normal practice.
      There is certainly a distinction to be made between Oilite and bronze, the former being a sintered product impregnated with oil ~ 18% the latter solid.
      A manufacturer will provide a variety of OD's and ID's within a nominal range to allow pressed in tolerance (close in ) using a variety of DOM and shaft material in their basic form which of course have their own tolerance. Machined housings allow the greatest control along with sized mandrels which control ID by permitting cold flow.
      Reaming is not an issue provided the tool is sharp though most Oilites are better single pointed.

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      • #4
        Yes, what Carm said.
        Don't know if you all picked up on it, but
        Mandrels can be used to size the bushings after they are installed.
        Sintered bushings size very easily.

        -Doozer
        DZER

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        • #5
          There are a great many things from Princess Auto that I would not trust, and calling some of what they sell as "bronze" to actually be anything close to bronze is wishful thinking IMO.

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          • #6
            You may well be correct!

            Originally posted by RussZHC View Post
            There are a great many things from Princess Auto that I would not trust, and calling some of what they sell as "bronze" to actually be anything close to bronze is wishful thinking IMO.
            . I parted off two of them, they machined as if they were sintered, but rather harder than if they were bronze or oilite bushings. They are used in a fairly simple steam tractor I am building for my grandsons so although they will likely be worked fairly hard when used they will likely see only a few dozen hours running each year. I have used solid bronze for the crankshaft bearings, the bushings are for the other 3 shafts in the transmission. Regards David Powell.

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            • #7
              HI David, I agree you might not be able to rely on PA tolerances, as we all know if made properly they should be able to be press fit into a reamed hole a get a running fit.

              iirc machinery's handbook gives the calculations - what the hole should be to give the resultant ID in the bearing. Never ream the bearing as you say, and if you follow the formulas and get the hole size right you shouldn't have to. You can also turn the OD of bearing on mandrel if easier...again to the formula's prescribed size.
              .

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              • #8
                David, you might want to try a magnet on one of those "bronze" bushings. IIRC, I once used some PA bushings and they WERE magnetic. I understand that it is an accepted practice to blend orange metal and iron in the sintering process, but I thought it was for high duty bearings, rather than "economy Oilite!"
                Duffy, Gatineau, Quebec

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