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  • Cool! (burnishing)

    There was a thread recently where the OP was a link to a YouTube video of a Russian machinist using a homemade burnisher on the lathe. I really liked the effect. He used a large bearing ball in a homemade holder, but what I did was use my pinch knurler with ball bearings in place of the knurls. I did grind a bit of a crown on the races.

    A finish pass of .005 or so DOC & .008 feed, then a pass half way with the pinch burnisher:

    Click image for larger version

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    The real thing looks much better than in the picture. Much smoother. I often use a file and emery cloth to get a nicer finish, but the burnisher beats that hands down.

  • #2
    Do you have a picture of the knurler?

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    • #3
      Originally posted by elf View Post
      Do you have a picture of the knurler?
      It's nothing special:

      Click image for larger version

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      • #4
        I tried something similar about three or four years ago. Made up a quick mount for a single small roller bearing to try and see what affect it would have on a 2 inch piece of schedule 40 common black pipe. Got a pretty decent finish on the black pipe with HSS tool bit ground with a relatively large radius cutting edge.
        I then mounted the makeshift roller bearing "burnisher" in the tool post at a very slight angle so as to enhance the unit pressure applied to the workpiece, only the very edge of the bearing made contact with the turned black pipe.

        Below a picture of the black pipe showing the before and after effect. The pic actually doesn't do it justice, it almost looks like polished stainless. I was surprised how little pressure was required to achieve the desired affect. Most likely due to the soft material. That piece is still in the shop and despite some wild swings in temp and humidity it remains rust free much like other pieces of carbon steel that have been polished that will also display an aversion to rusting.

        Home, down in the valley behind the Red Angus
        Bad Decisions Make Good Stories​

        Location: British Columbia

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        • #5
          I did similar to Willy's experiment but with aliminium;

          Location: Helsinki, Finland, Europe

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          • #6
            So actually your just rolling the surface... correct? I've never tried that before. Has anyone tried using any compounds along with the bearing?? Liquid polishing compounds, diamond pastes etc.

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

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            • #7
              Originally posted by JoeLee View Post
              So actually your just rolling the surface... correct? ...
              That's what I think. Just smushing down the peaks to fill in the valleys. The Russian guy was using it to get more precision, IIRC.

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              • #8
                Originally posted by Bob Engelhardt View Post

                That's what I think. Just smushing down the peaks to fill in the valleys. The Russian guy was using it to get more precision, IIRC.
                Anti-knurling

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                • #9
                  Originally posted by Bob Engelhardt View Post

                  That's what I think. Just smushing down the peaks to fill in the valleys. The Russian guy was using it to get more precision, IIRC.
                  I'm wondering how much you can smush the surface down or keep going over it before it starts to flake?? I know if I over knurl something all these little flakes start to accumulate in the knurls and tend to mess up the surface of the diamond pattern.

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                  • #10
                    Not sure about using polishing pastes - I can see them getting inside the ball bearings and doing them no good really quickly. I'd probably just glob some nice thick oil on the work & bearings, that's about all. Indeed, overdoing it will probably cause the surface to flake and spall.

                    Where I can see this being of benefit is when press fitting ball bearings onto shafts. The act of pressing the bearing on also squishes the peaks into the valleys and often means the resulting press fit is looser than expected. Giving it a pre-squish would stop this from happening.

                    Nice idea to use a knurling tool for this purpose! Roller burnishers are also available for bores, random pic: https://www.ebay.co.uk/itm/Cogsdill-...gAAOSwmzFfRGoE

                    Ian
                    All of the gear, no idea...

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                    • #11
                      Polishing compounds will do nothing good unless they are rubbed/swiped/slid across the surface. On a rotating bearing they would be embedded in the target surface, if anything at all.
                      Southwest Utah

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                      • #12
                        Nice work fellows !
                        Now you know something that does a great job with finishes
                        we used Cogsdill tooling on our Dies and gun drilled holes - awesome company
                        https://cogsdill.com/

                        Watch the light Lines !
                        Instead of using a surface comparator to check finish when on the lathe , use the "lightline"
                        In Post 5 you can see two lines of light in front of the little finger..The one on the right is the Light line and is reflecting
                        Light off the surface to your eye- Without stopping the lathe you can tell the finish you are achieving by looking at the lightline.
                        The narrower the line (thinning) the better the finish. (Yes , mirrors are nice, but the lightline still shows roughness)
                        Using a ball bearing (BB) is a good and cheap way to do it, how every not all radius's on BB are smooth, so look at the edges
                        The smoother the bearing surface the smoother your work surface becomes and your finish will never be better than that of the bearing.
                        So you knock down the peaks , but the Lightline still shows roughness because of waviness . Pressure now comes into play
                        and that means the workpiece and setup needs more rigidity

                        https://www.helpengineers.com/comple...s-and-symbols/


                        Rich
                        Green Bay, WI

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                        • #13
                          Originally posted by Rich Carlstedt View Post
                          Nice work fellows !
                          Now you know something that does a great job with finishes
                          we used Cogsdill tooling on our Dies and gun drilled holes - awesome company
                          https://cogsdill.com/

                          Watch the light Lines !
                          Instead of using a surface comparator to check finish when on the lathe , use the "lightline"
                          In Post 5 you can see two lines of light in front of the little finger..The one on the right is the Light line and is reflecting
                          Light off the surface to your eye- Without stopping the lathe you can tell the finish you are achieving by looking at the lightline.
                          The narrower the line (thinning) the better the finish. (Yes , mirrors are nice, but the lightline still shows roughness)
                          Using a ball bearing (BB) is a good and cheap way to do it, how every not all radius's on BB are smooth, so look at the edges
                          The smoother the bearing surface the smoother your work surface becomes and your finish will never be better than that of the bearing.
                          So you knock down the peaks , but the Lightline still shows roughness because of waviness . Pressure now comes into play
                          and that means the workpiece and setup needs more rigidity

                          https://www.helpengineers.com/comple...s-and-symbols/


                          Rich
                          Now I'm going to have to get one of those......

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

                          Comment


                          • #14
                            Originally posted by JoeLee View Post
                            I'm wondering how much you can smush the surface down or keep going over it before it starts to flake?? ...
                            On one of my first trials I went over it repeatedly and I did see flaking.

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                            • #15
                              Similar process in a roller box tool.

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