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A new attempt at making piston rings

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  • That is good. That drawing had me a little worried. Some back rake on top might help too.

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    • Yesterday I ordered a "fine India stone" from Norton. They don't cost much, and I don't have a lot in the way of sharpening stones. I bought a 1" x 4" stone. I have one big double sided stone that I inherited from my dad, and it works fine for sharpening jackknives and kitchen cutlery but isn't something you would use on material chucked in a lathe. Trimble recommends a "Fine India stone" as part of his write up on ring making.
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

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      • Originally posted by brian Rupnow View Post
        Yesterday I ordered a "fine India stone" from Norton. They don't cost much, and I don't have a lot in the way of sharpening stones. I bought a 1" x 4" stone. I have one big double sided stone that I inherited from my dad, and it works fine for sharpening jackknives and kitchen cutlery but isn't something you would use on material chucked in a lathe. Trimble recommends a "Fine India stone" as part of his write up on ring making.
        I regularly get those Norton 1x4 stones on eBay, they are absolutely the way to go for touching up an HSS edge.
        25 miles north of Buffalo NY, USA

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        • Originally posted by nickel-city-fab View Post

          I regularly get those Norton 1x4 stones on eBay, they are absolutely the way to go for touching up an HSS edge.
          Dat's cuz you have not used diamond hone sticks........
          2730

          Keep eye on ball.
          Hashim Khan

          Everything not impossible is compulsory

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          • Originally posted by J Tiers View Post

            Dat's cuz you have not used diamond hone sticks........
            I've used em and I hated em... tossed in the bin.
            25 miles north of Buffalo NY, USA

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            • Originally posted by nickel-city-fab View Post

              I've used em and I hated em... tossed in the bin.
              Why? That's where the india stone went (actually I kept it for use in scraping)
              2730

              Keep eye on ball.
              Hashim Khan

              Everything not impossible is compulsory

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              • Originally posted by J Tiers View Post

                Why? That's where the india stone went (actually I kept it for use in scraping)
                Tried both the ez-lap brand, and some knife-sharpening stones. The ez-lap has an area about the size of a postage stamp and the stick flexes. The knife stones have some goofball pattern in them and also flexed. Both conditions are unworkable, you need something that is a solid surface with zero flex. The Norton stone wins, at least for me: tried the rest and ended up liking the classic india stone the best.

                For heavy shaping and grinding I'm OK with diamond or CBN mounted on a grinder, -- they are great for that -- but not for handheld stones.
                25 miles north of Buffalo NY, USA

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                • Heavy-handed makes it flex. Diamond cuts with light pressure, flex is far less than your lack of precision guiding the lap. Whatever floats your watch, though.

                  Now back to the regular program.
                  2730

                  Keep eye on ball.
                  Hashim Khan

                  Everything not impossible is compulsory

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                  • Norton used to make diamond hones with a good solid aluminum backer, not sure if they still do.

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                    • I'm still a little puzzled by the "break" vs cut deal.

                      You'd think that breaking would need at least 0.004" of filing per side to get any reasonable surface, which brings it up to 0.008" of gap. You can get 0.008" slitting saws all day long.
                      2730

                      Keep eye on ball.
                      Hashim Khan

                      Everything not impossible is compulsory

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                      • I don't think it needs a reasonable surface in the gap. Doesn't matter what the surface looks like as long as there's some gap so the ring ends don't butt.

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                        • You need enough decent surface that the sides do not clash or still interlock.

                          That's the reason for question, because it is going to take some filing to ensure that the fractured surface no longer interlocks / interferes.and the ends can move freely. It seems that the fracture may work counter to that, based on how I see CI fracture in most cases. It is typically rough and peaky, not a clean cleaved surface. That's why the cracked apart con-rods work well, the surfaces engage well, with no tendency to shift around.

                          That may depend on the type of iron that is used. Or the method of doing the breakage may ensure a better surface than I have seen.
                          2730

                          Keep eye on ball.
                          Hashim Khan

                          Everything not impossible is compulsory

                          Comment


                          • Originally posted by J Tiers View Post
                            I'm still a little puzzled by the "break" vs cut deal.

                            You'd think that breaking would need at least 0.004" of filing per side to get any reasonable surface, which brings it up to 0.008" of gap. You can get 0.008" slitting saws all day long.
                            As I recall, the desired finished gap is around .004, so thats the max width saw kerf that could be used.

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                            • Originally posted by J Tiers View Post
                              You need enough decent surface that the sides do not clash or still interlock.

                              That's the reason for question, because it is going to take some filing to ensure that the fractured surface no longer interlocks / interferes.and the ends can move freely. It seems that the fracture may work counter to that, based on how I see CI fracture in most cases. It is typically rough and peaky, not a clean cleaved surface. That's why the cracked apart con-rods work well, the surfaces engage well, with no tendency to shift around.

                              That may depend on the type of iron that is used. Or the method of doing the breakage may ensure a better surface than I have seen.
                              "Clean cleaved surface" might be the key. The George Trimble method cleaves the ring with a special fixture, a sharp Vee shape with a mating backup section. That would give a much cleaner break line than CI fractures or breaking by hand. No doubt that is the reason for the fixture. How fine a grain the cast iron is also probably plays a part in the precision of the break even with the fixture.
                              Last edited by Sparky_NY; 06-09-2021, 09:31 PM.

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                              • What I have learned on this thread is that small 4-stroke singles are a real challenge. Brian's "Thumper" with its 1" bore and 1" stroke is a 13cc engine. The smallest commercial 4-stroke is the Honda GX25, which is twice the displacement of Thumper. https://engines.honda.com/models/model-detail/mini-4

                                The GX25 makes 1 HP @7000 RPM. It has the same stroke as Thumper, but has a 1-3/8" bore. eBay has ring and gasket kits, not too dear. I don't suppose that Thumper has space for a larger cylinder, but the availability of these kits might be a useful for some future engine.
                                Allan Ostling

                                Phoenix, Arizona

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