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  • Shear Pin

    I have shear pin which is about 3mm in diameter and 25mm in length. It's used to connect a hydraulic shaft which causes rotation motion to cause the convertible top to swing open.

    I'm wondering what material to machine it out of. I'm sure the original is steel but I'm not sure whether it just mild steel or hardened. I'm curious, are shear pins typically made of mild steel or hardened steel?

    I would test the original material with a file, but I not longer have this piece. It went flying when I was using a punch to push it out
    Last edited by rotate; 06-07-2009, 11:41 PM.

  • #2
    My advice would be mild steel , or aluminum.
    Hardened steel will most likely cause some thing else to fail.

    Steve

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    • #3
      I have had good luck with brass. Take a 1/8th brazing rod and turn it down if you don't have any brass drops laying around.

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      • #4
        Different kinds of shear pin.

        There are some pressure regulator pop offs that use a common nail for the shear pin. That might work if the size range corresponds.
        Byron Boucher
        Burnet, TX

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        • #5
          Check the original, even if it means buying from the main agent, SOME shear pins are "Spirol", "Roll" or "Selluck"?? pins.

          Regards Ian.
          You might not like what I say,but that doesn't mean I'm wrong.

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          • #6
            Originally posted by Circlip
            Check the original, even if it means buying from the main agent, SOME shear pins are "Spirol", "Roll" or "Selluck"?? pins.
            You got me worried. Can you explain the significance of these possibilities?

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            • #7
              I suspect the pins described are British equivalents of roll pins. They are are usually hardened and not intended to shear.

              Shear pins are mechanical fuses, and generally are of mild steel. It is a good idea to undercut the pin in the area where the shear will occur as this will prevent the ends from "smearing" and making the pin difficult to remove. The undercut can also serve to determine the shear strength.

              It is better to start with a too weak shear pin and increase the size or hardness until it holds at an acceptable level than starting with a too strong pin and risk damaging some other component in the system when it fails to do its intended job.
              Jim H.

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              • #8
                I have a packet of the original 40-year old shear pins that shipped with my Clausing 5914, and they're aluminum.
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                • #9
                  Yep, the shear pin on my MaxiMat screw cutting shaft is also aluminininium, but the shear/drive pin on one of the metal cutting chop saws I had to repair was a "Spirol", "Roll" or "Selluck" pin.

                  I tried with the alternative names I know of, cos I realise the little bu**ers undergo a name or sex change when they're transported over the Atlantic.

                  All the above (SAME parts, different names) are made from spring steel sheet, rolled into a tube and hardened and tempered. So just to set your mind at rest, before screwing the unit :-

                  Check the original, even if it means buying one from the main agent.


                  Regards Ian.
                  You might not like what I say,but that doesn't mean I'm wrong.

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                  • #10
                    Ian, don't confuse a shear pin with a drive pin. Roll pins are designed specifically not to shear. There is a difference in the application.
                    Jim H.

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                    • #11
                      Preciate what you say Jim, but a roll pin can satisfy both situations, had the "Whatever" pin been a solid hardened one in the chop saw it wouldn't have sheared. Have seen them used in many Drive applications and due to the construction allow a certain amount of Shock tolerance that's why I advocated to buy a dealer original. Chances are, as the original has sheared, the ends could have "Smeared", we don't know cos Rotate lost it. How much is it gonna cost?? If it's $200, once he's SEEN it,

                      Regards Ian
                      You might not like what I say,but that doesn't mean I'm wrong.

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                      • #12
                        I'm certain that it's a shear pin and it's designed specifically to shear when there's something blocking the tonneau cover of the convertible. I know this to be the case because that's what the dealership calls it and the pin sheared because I accidentally had a box on top of the tonneau cover which caused it to shear.

                        When I was hammering out the part I did noticed that one end of the pin was slightly tapered.

                        I would get the part from the dealer but they are back ordered (2 week delivery) and I need my top down asap.

                        Roughly speaking what is the shear strength of mild steel v.s. brass? Just a very rough figure? I find Google pretty useless for some basic information like this. Thanks everyone.

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                        • #13
                          Remember what Colour (Color) the bit you knocked out was ???
                          You might not like what I say,but that doesn't mean I'm wrong.

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                          • #14
                            Originally posted by Circlip
                            Remember what Colour (Color) the bit you knocked out was ???
                            Black. How does this matter?

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                            • #15
                              I second JC., Shear pins are from brass or aluminum. Hardened Roll pins are used as drive pins, never as shear pins. If you have a tapered pin it serves as a locating or as a drive pin. Never as a shear pin

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