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Can Teflon be machined to a very fine finish?

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  • Can Teflon be machined to a very fine finish?

    I got a piece of Teflon plate and a teflon rod for rolling epoxy putty into thin sheets. The idea was to do this without adding talcum powder, which prevents it from sticking. The idea didn't work. It sticks. I'm wondering if the surface of the Teflon is contributing to this. It has very fine, shallow lines in the surface, like it was cut with a very fine saw (I guess, anyway. It doesn't look milled).

    Can it be machined to a smooth finish? It's an inch thick, FWIW.

    Thanks. Lee

    BTW the application is for model building. Yesterday's experiment was for adding "Zimmerit" anti-magnetic coating to a 1/35 King Tiger tank. Rolled the putty into a sheet, added it to the tank, then used a paint bottle lid to roll the pattern into the putty.



    I figure it turned out alright for a first effort.

  • #2
    I was having trouble turning cheap, hot rolled round bar stock on my 91 year old lathe so that it had a smooth, silky, clean finish. No matter what I did, it always looked "groovy." But then I saw various people on youtube turning hot rolled using what's called a "vertical shear bit." Once I tried this, voila! I could turn very nice looking hot rolled pieces that were also very consistent in diameter across their length. I don't know if this method would work for Teflon, but IMO it's worth a try. I would probably also try cutting at the highest speed possible, but that's just a guess.

    Here's a Tubalcaine video on it (see part 2 after this one):

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    • #3
      From http://www.matweb.com/reference/Mach...nt-Design.aspx


      Finishes: There is continual demand for better finishes to improve product performance. Given the capabilities of modern CNC equipment, do not accept surface finishes above 63 micro inches from a machining vendor.

      A 32 to 40 microinch is considered a standard machined plastic finish for a +/- 0.005 toleranced component and should not incur any additional cost to produce.
      Finishes below 32 are reasonable and to be expected on close tolerance parts (+/- 0.0005).
      Finishes between 10 to 20 micro inches are typical for a polished plastic component especially as a turned component.
      Inside milled pocket finishes always have higher/worse finishes. The action of the nose of the endmill does not facilitate clean cutting and chip removal.
      Exterior flat milled areas can have a very good surface finish
      In 3D profile milling a good finish requires a large number of passes from a ball endmill. Carefully specify the maximum allowable finish to avoid excessive machine time.
      Finishes below 10 are difficult to achieve and may require lapping or similar with limited application to part geometry.
      Some plastics like Teflon cannot have a surface finish below 20 via any method because of the porosity of the material.
      You may not be able to get a smooth enough finish regardless of what you do.
      Location: Saskatoon, Saskatchewan, Canada

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      • #4
        I've used a tool with a round nose and it leaves the surface with a very smooth finish. The "soaplike" "lubricated" feel of Teflon makes it nonstick.
        Helder Ferreira
        Setubal, Portugal

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        • #5
          you might experiment with waxing it or using some armor-all on it or something.

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          • #6
            Very sharp blade (razor) leaves the best finish on plastic.
            Andy

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            • #7
              We used to have teflon machined to fine a finish. The company that did this used to use Liquid Nitrogen to solidify the teflon and then machine it.

              Mike

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              • #8
                I just realized that I forgot to mention that the Teflon bar has a smooth finish. The 1" thick plate could be better.

                I don't want to use oil for lube because the putty that gets rolled into sheets will be used on models and paint might not stick. Talcum powder is what I used yesterday for the experiment.

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                • #9
                  I think I'd try really getting a terrific polished sharp edge on my Stanley #6 plane and have a go a that 1" thick block of Teflon. Years ago I got a 2" thick piece of UHMW polyethylene and made a kitchen cutting board. Every so often, I skive off a bit by hand planing to renew it. Sometimes comes out mighty shiny and flat.
                  Last edited by Frank Ford; 10-27-2017, 01:01 PM.
                  Cheers,

                  Frank Ford
                  HomeShopTech

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                  • #10
                    Originally posted by Lee in Texas View Post
                    I just realized that I forgot to mention that the Teflon bar has a smooth finish. The 1" thick plate could be better.

                    I don't want to use oil for lube because the putty that gets rolled into sheets will be used on models and paint might not stick. Talcum powder is what I used yesterday for the experiment.
                    That's why i brought up the armor-all

                    heard it from a body shop guy it's one of his worst nightmares is when people use it on their cars trim and get some on the paint, years later and even though you scuff and prep the painted surface the new paint will not stick,

                    if you coated and then removed the excess with a clean rag it might be the ticket for it not sticking to the plate but maybe not effecting the putty's ability to adhere to other objects...

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                    • #11
                      Most plastics can be machined pretty well with razor sharp HSS tools and no lube. We have turned a lot of HDPE using cold air, venturi-type nozzles to keep the chips cool.

                      https://www.vortec.com/cold-air-guns

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                      • #12
                        Since you aren't dealing with heat, would polyethylene or polypropolene be an alternative? Both have surface energies a little higher than PTEF, but might have a better surface finish for your purpose. An theu are pretty cheap.

                        Ken

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                        • #13
                          I hate to be master of the obvious, but considering the very non-critical application, how about an ordinary wooden dough roller wrapped in saran wrap?

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                          • #14
                            I think you may need a separator sheet. Cling film has been mentioned already. And perhaps try parchment paper. Plus you may find that you need to wait for it to start stiffening up before peeling away one side of the paper then apply it to the part so it conforms to the shape and then roll in the pattern. This all means you're going to need to work fast if it is starting to stiffen up.

                            Or you may find that cling film on one side and parchment on the other works well and let's you work the putty earlier.
                            Chilliwack BC, Canada

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                            • #15
                              Many of these alternate ideas have merit, but make it kind of a bummer that the Teflon plate was 75 bucks after shipping.
                              Last edited by Lee in Texas; 10-27-2017, 01:36 PM.

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