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  • #31
    I found your write-ups interesting, just didn't have anything useful to add, except maybe post a couple of pictures. Of the threads, not your knuckles.
    Location: Long Island, N.Y.

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    • #32
      Agreed that solvents will increase shrinkage. They also do bad things to strength and chemical resistance. I saw a study somewhere that it only takes a very small percentage of solvent to cause a lot of physical property degradation in epoxy. If you need thin epoxy, use epoxy with reactive dilutants like U.S. Composites 635 (which is Reichhold 37-606). There is a big pool of this stuck to one of my lab benches where it got out of what appeared to be a well sealed mold. After that incident, I designed o-ring grooves into my sample molds and run silicone o-ring cord around the mold to prevent leaks. (I was making specimens for material testing, not nuts.)

      Searching back on the cnczone Epoxy Granite discussion, the moglice patent is here http://www.freepatentsonline.com/4329238.html and gives some ideas and moglice can be used for making nuts. The formula is pretty old.

      Anyway, I hope that this stream of consciousness is vaguely useful.

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      • #33
        Isn't this one of the applications for Moglice?
        Paul Compton
        www.morini-mania.co.uk
        http://www.youtube.com/user/EVguru

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        • #34
          I'm doing this project at work, so each day I go in I check to see how well the acme rods are turning in the plastic nuts. It seems that the more the epoxy cures, the less stiction there is. I may do nothing more than lap the rods one more time, which should loosen them up slightly. Nothing wrong with a near-mirror finish on them, as that will also mean less chance for the epoxy to get torn up by micro-mountains on the metal surface. They turn very smoothly now as it is, but are just a bit tight for my taste.

          The epoxy I'm using is Nu-Lustre 55. That probably means very little to anybody, but it has been good to me. The nuts I made from it several years ago have not become brittle, which I'm taking as a sign that it's a tough product. It reminds me of something called SuperMend, which I've also had very good results with. So far I've avoided the use of any metal filled epoxies in this type of application, but that $43 one liter can of metal filled filler still has me interested-

          I'll try to remember to take my camera in tomorrow and get some pics of the project.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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          • #35
            How does refrigerate before trying to remove the thread sound, even if the tread looked smooth and shiny i suppose there are a lot of hills and valleys to shear off before it lets go, more likely to shear below 5 for most epoxy, also the mould release, a thin film of PTFE is ok as a friction modifyer but no use as mould release, a dip in silicone oil leaves a film a bit thicker, a lot of these epoxies shink quite a bit during the cross linking of curing, hell of a grab, i beleive there are zero shrink ones too, id be tempted to try graphite spray on the rod as an experiment, had a good result with RF sheilding spray once, accidentaly btw!
            Anything new takes time, keep at it
            Mark
            Useless info, most of the casting epoxys are mede from cashew nut shells and corn husks!, hence the smell of popcorn if you cook them, at least that what the huntsman rep said, never actually checked, but they do smell nice when you high temp cure
            Last edited by boslab; 08-08-2014, 04:29 AM.

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            • #36
              Hi darryl
              Just thinking out loud here a little, but the Acne thread basically has for points of contact. The two walls serve to provide linear motion while contact
              with the top and bottom only add friction, at least as far as I can see. If you could chuck the nut up in a lathe and skim 1 or 2 thousands off of the
              peaks, that might remove some of the friction. If the lathe is not an option, maybe a reamer.
              Location: Long Island, N.Y.

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              • #37
                Skimming the bottom few thousandths seems like a good idea, especially if the bottoms of the acme threads aren't guaranteed to be ground.

                Originally posted by RichR View Post
                Hi darryl
                Just thinking out loud here a little, but the Acne thread basically has for points of contact. The two walls serve to provide linear motion while contact
                with the top and bottom only add friction, at least as far as I can see. If you could chuck the nut up in a lathe and skim 1 or 2 thousands off of the
                peaks, that might remove some of the friction. If the lathe is not an option, maybe a reamer.

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                • #38
                  Thanks for the ideas. These are rolled threads, and I cleaned them up pretty well. I expected them to 'interfere' in the epoxy threads anyway, and particularly because there is no real thickness to the ptfe coating. My goal was to have zero play, yet fairly easy turning. I got zero play, but I also got moderate turning resistance. It's something I can work with at any rate, and I'm happy with the result.

                  The top and bottom of the threads is every bit as important in achieving this goal as the walls are to the linear motion. I don't think I want to do anything to alter the nuts now, but as I mentioned I am going to lap the rods again. Because the fit is so close now, any material teased off the rods is going to result in a noticeable easing of the friction. I will sure have to clean the rods thoroughly before running them in again.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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