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Boring Bearing ID Do's & Don'ts

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  • Boring Bearing ID Do's & Don'ts

    I have an 1 3/4" ID flange bearing. I have to slip a piece of 6061 alum. tube through it. The tube varies a little on the OD. 1.749 to 1.757 on the highest point.
    It won't go through the bearing. I think the last time I ran across this with tube and bearings I had someone bore the bearing ID's out. But that was way before I had a lathe.
    So...... Can I cut the bearing steel with carbide??? I can scratch it with carbide so can I cut it?? Or should I set it up in the T&C grinder and grind the ID.
    I need to open it up about .008

    JL................

  • #2
    "Normal" practice is to make your shaft fit the bearing. First time you--or somebody else--has to replace the bearing
    the ID has to be modified again. If the tube OD varies that much and you turn the bearing to fit the high dim. then
    it's going to be sloppy on the low side. Sounds like all you need to do is throw the tube in the lathe and take some
    emery tape to it--"good enough" should be all you need. Or, if you actually want it to be precise, start with an oversize
    tube and turn it to fit properly...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

    Comment


    • #3
      Well, yes and no. Depending on application.
      This is for a friend. The aluminum tube and bearing are for an antenna mast / tower deal. The tube is 6' long so it ain't going in my lathe. Easiest thing to do is open up the bearing.

      JL...............

      Comment


      • #4
        Originally posted by JoeLee View Post
        Well, yes and no. Depending on application.
        This is for a friend. The aluminum tube and bearing are for an antenna mast / tower deal. The tube is 6' long so it ain't going in my lathe. Easiest thing to do is open up the bearing.

        JL...............
        Remove the tailstock and replace it with a steady rest. Grab the tube from the inside with the chuck. Use a very sharp bit to skim the end down
        so the bearing fits.
        Location: Long Island, N.Y.

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        • #5
          Originally posted by JoeLee View Post
          ...The aluminum tube and bearing are for an antenna mast / tower deal...
          Kinda changes things--not much precision required. I was assuming (?) that we were talking about something that
          would rotate at speed. I'd be tempted to just take a die grinder with a flap wheel to the ID of the bearing. Or just
          make something up out of UHMW--I've made lots of rotating antenna bases that way...
          Keith
          __________________________
          Just one project too many--that's what finally got him...

          Comment


          • #6
            Not much precision required at all for this job. Too much messing around to try and turn the tube because the bearing sets about 3' from the end of the mast.
            Easier to bore the ID of the bearing.

            JL.....................

            Comment


            • #7
              How are you planning on holding the inner bearing race, so that you can machine it?

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              • #8
                If you do (I wouldn't you you will likely need cbn... the bearing is way harder than is reasonable with carbide. A TP grinder would be your best bet.
                Last edited by lakeside53; 06-05-2018, 05:13 PM.

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                • #9
                  Hi
                  Such a small amount of metal to remove from the aluminium tube use a panel beaters rasp to remove the high spots until the bearing is a sliding fit and stick it in place with araldite no great precision required here. No + or - 0.0001" tolerance required here.
                  Or to quote some one with experience in this field
                  LKeithR
                  "Or just make something up out of UHMW--I've made lots of rotating antenna bases that way"...
                  Eric

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                  • #10
                    Originally posted by andywander View Post
                    How are you planning on holding the inner bearing race, so that you can machine it?
                    (Ad-hoc) faceplate and clamping ring/fingers.

                    Carbide will cut the bearing races, some grades are better than others. Tolerances are poop shoot because of high cutting forces but should work fine for this application. I would use sharp CBN insert just because I have them..
                    Location: Helsinki, Finland, Europe

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                    • #11
                      heck, if precision is of no interest, use a dremel and grinding stone while you clamp and spin it slowly (like 100rpm)

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                      • #12
                        Unless you take the bearing to 4 thou over. . Or leave it.. and turn shaft . Or sand shaft to fit..
                        You are going to have the tube falling out a.008 over.
                        What is the point of spending time to get that result.

                        At least turn a plug to press in the tube for one or both ends.

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                        • #13
                          Or get another chunk of tubing. Bring micrometer..

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                          • #14
                            or... go to the next size up bearing and put a fitted sleeve over the tube with the correct OD for the bearing ID.

                            or... 1.75" is 44.45mm. 45mm bearing inner, same outer? That's 20 'ish thou over.. and use some gap filling loctite.
                            Last edited by lakeside53; 06-05-2018, 05:49 PM.

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                            • #15
                              Most aluminium tube and bar is extruded. It's rarely round or to any specific size, even collets are a crap shoot when machining it.

                              Take lakeside53's advice!
                              Location- Rugby, Warwickshire. UK

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