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Hydraulic push rod material, HSS better than silver steel?

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  • Hydraulic push rod material, HSS better than silver steel?

    I have been using round HSS blanks as push rods for hydraulic ball sizing holes and tubes as HSS has bending and compressive strength that is unmatched by any ordinary steel, but they come in nominal increments, and I would like to have some variation to play with. If it comes close fit to the hole, it would be more self supporting and less prone to tilting. I'm afraid that, apart from kinking and bending the whole process, it can also damage the tube inner surface. The process requires application of several tons of pressure, so slight tilting will usually cause instant problems even for shorter tubes. I've used polycarbonate panel as a blast shield in case something springs off or shatters.

    So, I thought could I turn proper sized rods from silver steel (1.2210) and quench them and temper them to be as hard as possible, but not so to be brittle? Silver steel appears to have max HRC over 64, and even at 300C it still retains up to 60HRC hardness. It seems to be difficult finding tensile strengths for heat treated silver steel, but it's soft as mild steel in annealed state.

    This would be my first choice as I have it on stock and I have experience on making tools from it. However, should there be better materials for the purpose? I'm looking into something that's very high in bending and compressive strength, but tough enough not to shatter under extreme pressure.

  • #2
    You might look into Drill Blanks. They come in all the drill bit sizes and are already hardened.
    Kansas City area

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    • #3
      I believe those are the HSS round bars that I've been using. They are sold as HSS tool blanks for metalworking in all around the web.

      Well, I think I just gotta try out how silver steel works as press bar, and do some destructive testing how much it can take. For example, 8mm HSS blanks seem to hold up to at least 10-15 tons, likely much higher as I don't have any meter on my 50 ton jack and I have jacked it pretty hard sometimes. Compressive strength should be 3250MPa or about 325kg/mm2, or for 8mm over 16 tons until plastic deformation should occur. High carbon steels should have upper numbers at that same range, which could be equivalent to 60HRC silver steel, tempered just to remove the excess brittleness. However, HSS should also be quite brittle, and if it holds up, I believe SS would too.
      Last edited by amillertobe; 11-22-2021, 05:24 PM.

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      • #4
        Do you have access to a lathe and a tool post grinder? If so it should be fairly straight forward grinding a drill blank to a custom diameter. Is there anyone nearby capable of the setup?

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        • #5
          Do you buy carbide balls for this operation?

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          • #6
            I use ordinary ball bearings. They have worked great so far, because I don't commonly size materials that are harder than HRC40. Most common is ordinary steel.

            I do have lathe and a mill, so I could grind the tool blanks. HSS appears to be somewhat turnable with carbide inserts, so it could be an option. I might consider it.

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            • #7
              On occasion I turn commercial tap shanks normally using hard turning inserts, typical carbide inserts do not do well in this application, above 65 RC all bets are off.

              A hard turning tool is excellent for your application.
              Turn it hard and push the speed, it should spark at all times and the chip should come off glowing red.
              No coolant, the heat is your friend, close the door, if your lathe does not have an enclosure simply stand far away.
              The chips are very hot and will bugger you up in no time.

              This guy talks entirely to much but will give you the basics of hard turning.
              https://www.youtube.com/watch?v=T_upL1m12XU
              Last edited by Bented; 11-24-2021, 09:30 PM.

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              • #8
                Thanks for the info. I'll look into it.

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                • #9
                  Originally posted by Bented View Post
                  On occasion I turn commercial tap shanks normally using hard turning inserts, typical carbide inserts do not do well in this application, above 65 RC all bets are off.

                  A hard turning tool is excellent for your application.
                  Turn it hard and push the speed, it should spark at all times and the chip should come off glowing red.
                  No coolant, the heat is your friend, close the door, if your lathe does not have an enclosure simply stand far away.
                  The chips are very hot and will bugger you up in no time.

                  This guy talks entirely to much but will give you the basics of hard turning.
                  https://www.youtube.com/watch?v=T_upL1m12XU
                  Hey! I agree with all of it.

                  Turning HSS or any other tough metal will produce sparks and glowing chip. Just the way it is.

                  I have watched machinists get freaked out and think there is an issue. Yeah, just make sure yer chip tray is clear.

                  If I am cutting hard metal and I dont get a shower of glowing swarf I am ruining my tool bit and not actually cutting. Just rubbing.

                  I like that I can cut hard metal in my home shop. Not that I do it on the daily, just that if I need to I can. All you guys cn. Right tool for the job is all. JR

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                  • #10
                    It will also burn the paint, do not hard turn if the painted surfaces in the chip path are important features of the machine.

                    Paint is important, most machines will not function correctly if the paint us barked up.

                    Use machine.
                    Strip scratched paint from machine.
                    Repaint machine.

                    Repeat daily.

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                    • #11
                      Originally posted by Bented View Post
                      It will also burn the paint, do not hard turn if the painted surfaces in the chip path are important features of the machine.

                      Paint is important, most machines will not function correctly if the paint us barked up.

                      Use machine.
                      Strip scratched paint from machine.
                      Repaint machine.

                      Repeat daily.
                      Hahaa. Now you are being a Capitol D. Paint? What the heck is that all about? Are you trying to bag on folks here that might like to put a nice new coat of paint on it?

                      Hey, paint is protection from the elements. Thats all. It helps to keep the rust from rusting. JR

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                      • #12
                        The best protection from rust is a heavy coating of iron oxide (-:

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