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  • Delrin/Acetal

    Anyone have any experience working w/ it? Can it be knurled & tapped & will it hold a set screw?

  • #2
    delrin can be drilled and taped and hold threds but dont over tighten min yu that also depends on the size of threds your talking about as well..
    delrin is pretty tough stuff either way.. machines really nice with HSS cutters , i made a muzzle break and a few other odds and sods out of the stuff ..


    • #3
      It's easy to machine on the lathe or mill. Chips are less troublesome than most other plastics. It's one of my favorite materials.

      I machined this pulley wheel from red Delrin:

      Any products mentioned in my posts have been endorsed by their manufacturer.


      • #4
        Evan implies that knurling of Delrin is possible, here: I admit to being surprised, thinking that acetyl lacked the required ductility for this operation. But the proof is in the pudding.
        Allan Ostling

        Phoenix, Arizona


        • #5
          I knurled some 15mm Delrin with my scissor type knurling tool without any problems.



          • #6
            Delrin knurls just fine as does acetal. Delrin and generic acetal are different products with different properties. Delrin is acetal homopolymer and generic acetal is acetal copolymer. The main differences:

            Delrin is stronger by about 20 %
            Delrin has very poor acid resistance
            Delrin is prone to center zone porosity in extrusions.

            Generic acetal copolymer is weaker.
            Acetal copolymer has good acid resistance, especially in food applications.
            Acetal copolymer has uniform density.

            There are other minor differences in rated service temperature but they aren't significant for most applications. The big item is the chemical resistance and that makes Dupont Delrin entirely unsuitable for food processing applications where exposed to acidic materials such as ketchup or orange juice etc.

            As for knurling, it tends to spring back so it is necessary to use a good sharp knurler and works better with a coarser knurl.

            The center ball and grip part is acetal, the ends are made from remachined PVC plumbing fittings.

            Free software for calculating bolt circles and similar: Click Here


            • #7
              Where did you get the red delrin? I could have used that many time!


              • #8
                What Evan missed out on but can be clearly seen on the Knurled ring is that it's better to use a threaded metal insert rather than rely on tapping the material.

                My mid sixties radio control gear uses "Acetal Copolymer" moldings for the servo cases and the gear trains. The case halves are screwed together but the threads are quite long in the material and you aren't taking them apart very often.

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


                • #9
                  That isn't a threaded insert. It's a short piece of all thread rod that is threaded into the ball with a nut threaded on to lock it in place as it was wound in. The exposed portion is what screws into the bottom of the camera body.

                  Delrin takes threads well. Of course it isn't as strong as metal in the regard but it will hold very well if a few more threads are provided. Coarse thread is the rule.
                  Free software for calculating bolt circles and similar: Click Here


                  • #10
                    Didn't like the turning anyway
                    You might not like what I say,but that doesn't mean I'm wrong.


                    • #11
                      Thanks for all the info. Will talk to my customer tomorrow & see what he wants to do.


                      • #12
                        Knurling Delrin Rod

                        THe cutting style of knurling tool does a great job on Delrin and PVC. I'd love to have one but they are unreasonably expensive
                        Jim (KB4IVH)

                        Only fools abuse their tools.