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A new attempt at making piston rings

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  • #16
    Due to Covid shutdowns and my own impatience, I will wrap a piece of 220 grit emery cloth around a wooden dowel and use that to deburr the inside/edges of my rings. Someday, when this damned plague is over, my wife and I will drive down to Vaughn and pick up one of these tools from Lee Valley Tools.
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

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    • #17
      An excellent tool for measuring this sort of thing is an internal groove micrometer when the groove is more then .050" wide, whilst not intended for external work they are fine in many circumstances and are relatively inexpensive.

      A mitutoyo .050-1"
      Last edited by Bented; 04-21-2021, 08:22 PM.

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      • #18
        And here we have a quick and nasty round ceramic file (220 grit emery paper glued around a turned broom handle), and my rings are all deburred on the inside/edges. Tomorrow I will break them in a vice, file the ends, try them for size in a cylinder, and then heat treat them.
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

        Comment


        • #19
          Why break them? It seems that a slit with a fine saw would be better, and every ring I have put in any small engine is either a regular slit type, or one with an "L" shaped overlap cut, which a break does not emulate.

          Per your "rules" list, you would have to file the ends, which is likely to make an opening that is about as large as the saw gives. The actual will be whatever you have to file. The saw gives a known and predictable result. You have to have an opening, or expansion will potentially close them up tight and jam.
          2730

          Keep eye on ball.
          Hashim Khan


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

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          • #20
            Originally posted by J Tiers View Post
            Why break them? It seems that a slit with a fine saw would be better, and every ring I have put in any small engine is either a regular slit type, or one with an "L" shaped overlap cut, which a break does not emulate.

            Per your "rules" list, you would have to file the ends, which is likely to make an opening that is about as large as the saw gives. The actual will be whatever you have to file. The saw gives a known and predictable result. You have to have an opening, or expansion will potentially close them up tight and jam.
            Yes. Adequate ring end gap is critical.

            -js
            There are no stupid questions. But there are lots of stupid answers. This is the internet.

            Location: SF Bay Area

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            • #21
              Originally posted by brian Rupnow View Post
              eKretz---I think that is taken care of by sliding the rings around in a figure 8 pattern on a sheet of fine emery cloth, or on a sheet of glass with lapping paste.
              Oops! I was thinking you were describing the cutting of the ring grooves.

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              • #22
                Originally posted by brian Rupnow View Post
                This is an "end" of cast iron that I have had for years. It has been turned down to 1.000" outside diameter and bored to 0.898" inside diameter. Now comes the parting off and deburring. I will get as many .063"-.064" wide rings out of this as I can.
                Turned finish only on the OD or did you work it with fine emery paper?

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                • #23
                  How do you end up with a .004 end gap, if you slit the ring with a .020 saw?
                  per your list of recommendations?

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                  • #24
                    Sparky---the ring o.d. was brought to within a couple of tenths of finished size, then worked down with emery to be 1.000" diameter. The center was then bored to 0.898" by drilling, then boring.
                    Last edited by brian Rupnow; 04-22-2021, 10:51 AM.
                    Brian Rupnow
                    Design engineer
                    Barrie, Ontario, Canada

                    Comment


                    • #25
                      Ringo--You have to read all of the posts carefully to see what's happening here. Philip Duclos suggests using a 0.020" slitting saw to cut the rings, and if you do that, the Philip Duclos method says that you have to add in the thickness of the saw when doing the ring diameter calculation so (3.14 x 1" +.020)/ 3.14 which brings the o.d. of the unbroken ring to 1.006". George Britnell suggests not sawing the ring at all, but turn the o.d. to the finished cylinder diameter, breaking the ring (which removes no material) and then filing the gap with a points file to achieve the 0.004" gap.
                      Brian Rupnow
                      Design engineer
                      Barrie, Ontario, Canada

                      Comment


                      • #26
                        I always wondered why they don't use a method more like:

                        Turn the ring roughly to O.D. size and slightly over desired finished I.D size, part off and cut open. Make a fixture that has a pilot with width sticking out that is ~90% of the ring thickness with a basic O.D. less than the desired ring O.D. and the pilot diameter at the desired ring I.D. - the fixture should have a tapped hole in the end to mount a pinch plate that pinches the ring on its sealing faces. Put the ring over the pilot, mount the pinch plate and squeeze the ring down snug (not too tight, don't want to introduce distortion) to the pilot diameter with something like a hose clamp, then tighten the pinch plate. Finish the ring O.D. When the pinch plate is removed, the ring will spring open slightly - amount depending on whatever difference you made the I.D. of the ring and the O.D. of the pilot.

                        This seems like it would make about the roundest rings at the truest diameter that would be possible. I never tried this, just thought up this method after seeing all the different ways people describe making rings that don't seem all that great in terms of keeping the rings round and true.

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                        • #27
                          The rings have all been split. This is a very simple procedure where part of the ring is clamped in the vice and one half sticks out the end of the vice where it can be grabbed by my finger and them and gently pushed back and forth until it cracks. You have to be careful with your pushing and pulling, as you don't want to snap the ring in two pieces. At this point in the game, the rings are still the same i.d. and o.d. as they were when machined.

                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

                          Comment


                          • #28
                            eKretz---There is a man, Professor Chadock, who advocates using a set up much as you describe and then grinding (or turning) the rings to a perfectly round outer diameter. The more you look into making rings, the more different opinions you will see. They all work.
                            Brian Rupnow
                            Design engineer
                            Barrie, Ontario, Canada

                            Comment


                            • #29
                              I have made a heat treat fixture on which to mount the rings. Trial and error showed me that making the inside diameter of the fixture 0.942" diameter and forcing the rings over it resulted in a 1/8" gap between the ends of the ring. I truly felt that if I spread the rings any wider they were going to break. The rings are tightly compressed between the two discs to keep the broken ends of the rings perfectly in line. The back-side of the fixture has been hollowed out so it will have less mass to heat up. I will heat fixture and rings to a cherry red with my oxy acetylene torch, being sure not to let the torch flame play directly on the rings. The ring ends will be filed after the heat treat is finished and the rings demounted.
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

                              Comment


                              • #30
                                After being heated cherry red, and left to air cool, then a little bit of clean-up, the rings have all taken a new "set" and the gaps remain open about 1/8" after they are removed from the fixture. I have seen on Youtube where some people heat the rings to cherry red, then drop them into a bucket of oil or water while they are still cherry red. I have no idea why they do that, and I've never read anything saying that this is a part of the process. My next step will be to square up the broken ends and test fit them into a cylinder to check that I have about 0.004" gap between the ring ends.
                                Brian Rupnow
                                Design engineer
                                Barrie, Ontario, Canada

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