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  • #16
    That's nice, I wish I had one. If it is better than 0.0001" it is plenty good enough for the real world, after the people who work to smaller dimensions don't actually produce anything, they just boast about their instrumentation.

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    • #17
      Originally posted by old mart View Post
      That's nice, I wish I had one. If it is better than 0.0001" it is plenty good enough for the real world, after the people who work to smaller dimensions don't actually produce anything, they just boast about their instrumentation.
      Thank you! It is exactly .0001 taper so far. I still need to check the actual squareness. I figured there was no point going finer than .0001 since that is the limit of my ability to measure. For my shop, anything finer than that is wasted, except for the slips or gauge blocks. This surplus piston pin will be my standard for squareness.
      25 miles north of Buffalo NY, USA

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      • #18
        Don't forget to check it both ways round.

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        • #19
          Originally posted by old mart View Post
          Don't forget to check it both ways round.
          How do you mean? By turning it end for end? I will try to be as thorough as possible. The tenths indicator is very fussy, the smallest influence makes it jump.
          25 miles north of Buffalo NY, USA

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          • #20
            Yes, end for end, probably both will be good, but if one isn't, then it will have to be marked, maybe with a lifting handle in the bore. The ones where I worked were single ended with a smaller diameter knurled handle projecting from the top.
            Last edited by old mart; 02-02-2020, 01:28 PM.

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            • #21
              Originally posted by old mart View Post
              Yes, end for end, probably both will be good, but if one isn't, then it will have to be marked, maybe with a lifting handle in the bore. The ones where I worked were single ended with a smaller diameter knurled handle projecting from the top.
              OK, thanks. It has taken me an hour to come up with a possibly valid test setup, but I'm not sure and I am not liking what I am seeing. It was a question of finding a way to hold the indicator solidly enough because it is so sensitive. I am measuring near the top of the cylinder, not the base, on the belief that the greatest error will be shown there. I am seeing around 6 tenths out of square, and I am wondering about lappping it. However the setup does not repeat very well, and I want to trust me measurements before I decide anything. Bluntly, I think my setup is a bit flimsy, and I will keep trying different methods and report back.
              25 miles north of Buffalo NY, USA

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              • #22
                The cylindrical squares are made by truing the end on a cylindrical grinder. The end has to be square to the sides, assuming the sides are not tapered, it cannot be otherwise. You could run the pin in your lathe with the end against a diamond lap in the toolpost. The base of cylinder squares is produced as a fairly thin ring to eliminate the possibility of rocking on a spherical surface, your pin has the thin edge already.
                Testing the end for squareness would also be easier if you put it in the lathe in a four jaw chuck and got it running fairly true. As long as the pin was parallel to the lathe axis, then the end/s could be indicated for squareness. Say, if the runout at the chuck end was 0.001" and that runout was in the same place at the end, then the radial error would not matter at all.

                I've just looked on ebay UK for large gudgeon pin (UK equivalent of piston pin or wrist pin) and only got motorcycle and a BMW car one, too small by far.
                Last edited by old mart; 02-02-2020, 04:04 PM.

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                • #23
                  I have a much more solid setup now, using the height gauge to hold the indicator. It has confirmed that it is .0006 out of square. Unfortunately I am without a lathe altogether at the moment, so everything I do is on the surface plate. I have some 600-grit paper available, and an arkansas oil stone that is so flat that it will "wring" like a gauge block.

                  Considering this pin is probably as old as me, that's pretty good manufacturing tolerances. It could be better though if I'm going to use it for metrology.
                  Last edited by nickel-city-fab; 02-02-2020, 04:05 PM.
                  25 miles north of Buffalo NY, USA

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                  • #24
                    Originally posted by old mart View Post

                    I've just looked on ebay UK for large gudgeon pin (UK equivalent of piston pin or wrist pin) and only got motorcycle and a BMW car one, too small by far.
                    Try this, the seller has more than 10 available. Shipping may be expensive though.

                    https://www.ebay.com/itm/Sealed-Powe...53.m1438.l2649

                    I have just turned the pin end-for-end and obtained much better results: a tenth repeatably. Measuring across the diameter in the "notch" at the base of a surface gauge.
                    25 miles north of Buffalo NY, USA

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                    • #25
                      There you go, make a handle for the bad end, done and dusted as we say in Blighty. Unfortunately the shipping charges from the USA are so ridiculous that I have only ever bought one item from there.

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                      • #26
                        Originally posted by old mart View Post
                        There you go, make a handle for the bad end, done and dusted as we say in Blighty. Unfortunately the shipping charges from the USA are so ridiculous that I have only ever bought one item from there.
                        That's unfortunate. I have routinely bought Whitworth and BA tap sets and etc via eBay UK, and I thought the shipping was reasonable, if a bit high.

                        I really wish the other end was better because there is a through hole across now on the upper portion of the pin. Said hole was originally used for a bolt to retain the pin in the piston. I had wanted the hole near the bottom, on the surface plate. Click image for larger version

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                        25 miles north of Buffalo NY, USA

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                        • #27
                          Originally posted by nickel-city-fab View Post
                          I have a much more solid setup now, using the height gauge to hold the indicator. It has confirmed that it is .0006 out of square. Unfortunately I am without a lathe altogether at the moment, so everything I do is on the surface plate. I have some 600-grit paper available, and an arkansas oil stone that is so flat that it will "wring" like a gauge block.

                          Considering this pin is probably as old as me, that's pretty good manufacturing tolerances. It could be better though if I'm going to use it for metrology.
                          As oldmart indicated, you need an end that is perpendicular to the sides. This means it must also be flat. Perfectly flat. In the photo the end does not not look flat at all. Should be looking much like the sides. You need to assure that the end is flat. Preferably a thin ring near the od. Then your measurements should be repeatable. A proper squareness checker would also help. If you are still using what is shown in photo 2, good luck is all I can say.

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                          • #28
                            Originally posted by rickyb View Post

                            As oldmart indicated, you need an end that is perpendicular to the sides. This means it must also be flat. Perfectly flat. In the photo the end does not not look flat at all. Should be looking much like the sides. You need to assure that the end is flat. Preferably a thin ring near the od. Then your measurements should be repeatable. A proper squareness checker would also help. If you are still using what is shown in photo 2, good luck is all I can say.
                            Thankfully I got a better measuring setup figured out, and it is indeed repeatable. Using the vertical notch in the Starrett base. The ends have a heavy chamfer on them, but I think they'll be OK. Currently correcting it using the method outlined here: https://www.youtube.com/watch?v=m4mH120Lf68
                            25 miles north of Buffalo NY, USA

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                            • #29
                              Originally posted by old mart View Post
                              There you go, make a handle for the bad end, done and dusted as we say in Blighty. Unfortunately the shipping charges from the USA are so ridiculous that I have only ever bought one item from there.
                              how would you fasten the handle to the end ?
                              You you can't drill and tap, if you tack weld you'll probably distort it
                              About about all you could really do is epoxy some sort of handle inside it.


                              JL......

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                              • #30
                                Originally posted by JoeLee View Post
                                how would you fasten the handle to the end ?
                                You you can't drill and tap, if you tack weld you'll probably distort it
                                About about all you could really do is epoxy some sort of handle inside it.


                                JL......
                                That's a good question. I think it would be best to turn up a round piece of whatever and loctite it in.
                                25 miles north of Buffalo NY, USA

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