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  • #31
    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......
    One thought, since you mentioned it is around a tenth tapered, would be an expanding plug to mount the handle. The tension needed to lock the handle in place might just stretch out some of that taper.

    You asked about lapping. I agree with the others that mentioned that the end of wrist pins don't need to be super accurate so it's possible that the surface isn't as flat as you think. So I'm thinking that it SHOULD be lapped if only to check for flatness. The pattern made by the beginnings of the lapping will show this very quickly. But just as importantly to ensure a really nicely flat surface with very little roughness to ease the movement around on the surface plate. I think I'd also want to somewhat relieve the inner half or even 2/3's of the ends so the seating is all out on the furthest part of the end. And as long as you're at it you might as well lap it with testing to work it square.

    When I did my own shop made cylinder square I found that simply pushing it across the lapping surface so the side needing the most removed was leading and the torque of pushing it from behind with one finger about an inch or so up of the bottom was enough difference to remove the few tenths needed in short order. And I either got lucky or it was a good way to do the squaring up because it took very little effort and no really undue control to take out the lean to where any remaining error was not noticeable with the squareness comparator I was using.
    Chilliwack BC, Canada

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    • #32
      Originally posted by BCRider View Post

      One thought, since you mentioned it is around a tenth tapered, would be an expanding plug to mount the handle. The tension needed to lock the handle in place might just stretch out some of that taper.

      You asked about lapping. I agree with the others that mentioned that the end of wrist pins don't need to be super accurate so it's possible that the surface isn't as flat as you think. So I'm thinking that it SHOULD be lapped if only to check for flatness. The pattern made by the beginnings of the lapping will show this very quickly. But just as importantly to ensure a really nicely flat surface with very little roughness to ease the movement around on the surface plate. I think I'd also want to somewhat relieve the inner half or even 2/3's of the ends so the seating is all out on the furthest part of the end. And as long as you're at it you might as well lap it with testing to work it square.

      When I did my own shop made cylinder square I found that simply pushing it across the lapping surface so the side needing the most removed was leading and the torque of pushing it from behind with one finger about an inch or so up of the bottom was enough difference to remove the few tenths needed in short order. And I either got lucky or it was a good way to do the squaring up because it took very little effort and no really undue control to take out the lean to where any remaining error was not noticeable with the squareness comparator I was using.
      Thank you, I am indeed lapping it in right now. First lesson I learned is that it goes a lot faster and easier with diamond. I got those cheap ones at Harbor Freight. Yes the texture on the ends isn't all that great as-machined. The lap is making it look like a mirror polish. The wall thickness is about 3/8 (10mm) but there is no way for me to make a lip. I'll have to live with it. I'm checking it every few minutes with the indicator, and using baby oil on the diamond hone. I've got all day.

      That's interesting about using a plug to expand one end, do you really think that would work in spite of the wall thickness?
      25 miles north of Buffalo NY, USA

      Comment


      • #33
        I would just Loctite or glue the handle in and forget about trying to expand the pin. It would only be a bulge at the tightest point at best. It is pretty good at present and attempting to lap it on anything less than an optical flat is a waste of time. And then only if the optical flat is binned afterwards.

        Comment


        • #34
          That's interesting about using a plug to expand one end, do you really think that would work in spite of the wall thickness?
          You're only looking for a tenth or so. And if metal working to fine amounts like this has taught me anything it is that everything we use is like an elastic band.

          I'd go with two tapered cones and a split sleeve with same angle conical spots at each end between. The handle being the tightening screw to lock the setup. I'd likely also make this handle plug about 1/3 as long as the pin so it stretches the upper 1/3 of the pin. Tighten and check until the taper zeros out or you are worried about shearing off the threaded "handle" you're using to tighten the plug. Can't hurt, might help and it's not that complicated to produce and use for a good permanent handle? And I rather suspect that you'll be able to stretch out that last tenth without that much trouble.

          I read that there was a display at one of the early World Expositions. Either the one in Paris or the one in London. It was a piece of roughly 3ft tall structural I beam about 8ft long as I recall. It was perched on supports at each end and had a VERY sensitive indicator gauge testing the middle of the beam. Delicate ladies at the time were able to push on the beam and the indicator dutifully swung through some impressive looking arc of travel. After which everyone jokingly complimented the lady on their brute strength. So yeah, if we're looking for a small enough movement then even the best of steels in the heaviest of sections are like cheap elastic bands.
          Chilliwack BC, Canada

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          • #35
            I wonder if I am truly scrwed and/or stuffed. I try to lap in the "bad" end and it doesn't get any better, the best I can get it is like 2 thou. The "good" end is somewhat better but its still discouraging with a "tenths" indicator... just walking nearby (wood floor) gives it the wiggles.

            I'll keep at it and report back. Worse comes to worst I'll have to get someone with a grinder.

            The entire experience gives me a *lot* of respect for people like Maudslay and Whitworth. And millions of others since ancient times.
            25 miles north of Buffalo NY, USA

            Comment


            • #36
              Guy Lautard had an account of going to an older German toolmaker to get a square block checked and corrected as needed with the last little bit. The toolmaker had a nice trick for biasing the part that needed to be cut down to bring the part true. He had a lapping plate and stuck a mag base to the high side of the square. Then just used figure 8 lapping like he was just working for flatness. The slight weight bias got the correction he needed.

              Also, it occurs to me that you have an interesting opportunity with your .0001 taper. Think about the cylinder leaning to one side to correct for the taper. If you lapped your cylinder flat, but off-square by a fraction of the tenth taper, you could measure and mark one location as correctly square, in spite of the taper. It means that the opposite side would be .0002 out of square, and at 90 degrees you'd see .0001 out of square. You'd have to pay attention to how you used it, but you can get really true geometry in spite of the taper error.
              .
              "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

              Comment


              • #37
                Yes, you can buy squares like that.... the end is ground to be just off square, and the true points are marked. They will actually measure the out of square, by how far from the true spot you have to turn them to fit up.

                It's not a defect, it's a feature.
                2730

                Keep eye on ball.
                Hashim Khan


                It's just a box of rain, I don't know who put it there.

                Comment


                • #38
                  Originally posted by J Tiers View Post
                  Yes, you can buy squares like that.... the end is ground to be just off square, and the true points are marked. They will actually measure the out of square, by how far from the true spot you have to turn them to fit up.

                  It's not a defect, it's a feature.
                  Yep, I've seen them. Definitely out of my budget, even on eBay. Hence, trying to "lap in" my own, but man it is slow going.... I decided to start with the worst part this morning, lapping on the end. Slowly getting better at ti but I have miles to go. I have a sheet of glass fastened to an old drawing board, I can tape emery paper on that. I also have a selection of arkansas and norton stones, and some cheap diamond stones. I'm keeping everything wet in a mixture of baby oil and kerosene in a pan.
                  I need to do the trig and find out how much. The worst part is still .002 out over a 6" length.
                  25 miles north of Buffalo NY, USA

                  Comment


                  • #39
                    If it is 2.5" diameter, and 6 long, then for every 0.0005 you take off one side of the face, you should be changing the tilt by 6/2.5 x 0.0005", or 2.4 x 0.0005 = 0.0012" in 6". So you won't be wanting to take much off.

                    I like the weighted side idea. that would give reasonable bias, and you would not want to do any down-pushing, because that is hard to control.

                    It actually takes quite a lot of time and rubbing, I have found, to take off even a couple tenths from hardened steel. Actual honing oil may be better than the mixture, but whatever works OK.
                    2730

                    Keep eye on ball.
                    Hashim Khan


                    It's just a box of rain, I don't know who put it there.

                    Comment


                    • #40
                      Even worse news Nickle. I have now confirmed Fairbanks made 20hp engines of the same Z design. You'll need to start over. Maybe if you're lucky you can claim the 18 was practice and get work credit for it.
                      Sorry bout dat.

                      Comment


                      • #41
                        Originally posted by J Tiers View Post
                        If it is 2.5" diameter, and 6 long, then for every 0.0005 you take off one side of the face, you should be changing the tilt by 6/2.5 x 0.0005", or 2.4 x 0.0005 = 0.0012" in 6". So you won't be wanting to take much off.

                        I like the weighted side idea. that would give reasonable bias, and you would not want to do any down-pushing, because that is hard to control.

                        It actually takes quite a lot of time and rubbing, I have found, to take off even a couple tenths from hardened steel. Actual honing oil may be better than the mixture, but whatever works OK.
                        I certainly doesn't help that I screwed up and honed the wrong side... it went the other direction by the same amount, bearing down hard on a coarse diamond plate. *sigh* will keep trying. Thanks for the explanation. At least the bottom is nice and shiny.
                        25 miles north of Buffalo NY, USA

                        Comment


                        • #42
                          Originally posted by old mart View Post
                          I would just Loctite or glue the handle in and forget about trying to expand the pin. It would only be a bulge at the tightest point at best. It is pretty good at present and attempting to lap it on anything less than an optical flat is a waste of time. And then only if the optical flat is binned afterwards.
                          My first thought was to plug the bottom with something, a wax plug, cork etc. Suspend the handle over the hole and pour some epoxy or Devcon type material in the hole.
                          You wouldn't have to have a very deep hole, depending on the weight of your pin. I would also rough up the the inside wall so the epoxy has something to grip.

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

                          Comment


                          • #43
                            Originally posted by Franz© View Post
                            Even worse news Nickle. I have now confirmed Fairbanks made 20hp engines of the same Z design. You'll need to start over. Maybe if you're lucky you can claim the 18 was practice and get work credit for it.
                            Sorry bout dat.
                            heh heh heh practice makes perfect.... It makes me really appreciate what people did in the days before electric motors
                            25 miles north of Buffalo NY, USA

                            Comment


                            • #44
                              You might want to grind-in some small relief slots in the end. Not too deep, just enough that when you are using it, or lapping it, that any pieces of crud that get on the surfaces have somewhere to go.

                              Most of the commercial ones have something similar for that reason.

                              As for handle, a piece loctited in should be fine. The expanding handle idea would work also, and be removable. I have quite a few go-nogo gages, some of the larger ones are rings, and appear to be held by an expanding part on the handle.
                              2730

                              Keep eye on ball.
                              Hashim Khan


                              It's just a box of rain, I don't know who put it there.

                              Comment


                              • #45
                                Originally posted by nickel-city-fab View Post
                                I wonder if I am truly scrwed and/or stuffed. I try to lap in the "bad" end and it doesn't get any better, the best I can get it is like 2 thou. The "good" end is somewhat better but its still discouraging with a "tenths" indicator... just walking nearby (wood floor) gives it the wiggles.

                                I'll keep at it and report back. Worse comes to worst I'll have to get someone with a grinder.

                                The entire experience gives me a *lot* of respect for people like Maudslay and Whitworth. And millions of others since ancient times.
                                This is what I tried to express in my first response to you. You are going in the right direction now. Couple of things still need to be addressed. Are you measuring and documenting the squareness of each measurement. Have you located the zero plane which should repeat at 180 degrees? (Or at least within your taper dimension.). Now measure again and again to see if you have repeatability. Next write the squareness on top of the pin for reference. Measure and log 0-90-180-270 on top of the pin. At this point you are ready to lap, not before. Your squareness checker still sounds iffy. The Suburban video does not show the base of the squareness gage. It will have a horizontal radiused blade that contacts the cylinder. I don't see working in 1/10s without one.

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