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vibratory polishing and protecting 28 tpi threads

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  • vibratory polishing and protecting 28 tpi threads

    So I may be making batches of parts that I want to polish which have 1x28 tpi and 7/8x28 tpi threads. I'm assuming they need to be masked somehow. Any suggestions?

  • #2

    I would polish before threading if possible. But if you must thread and then polish, I would use a softer media like walnut. But most anything you do will round the thread profile.

    If you think you understand what is going on, you haven't been paying attention.


    • #3
      Just use a non toping insert, then insted of polishing making the thread profile less accurate, Its making it more accurate..
      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


      • #4
        just throwing it out there... never tried it, but maybe dip the threaded sections in wax? Then you could easily remove the wax from any areas still to be polished, but keep the threaded sections safe.


        • #5
          I've used Plastidip for protection when sandblasting. It might work for what you are doing.


          • #6
            I would imagine that wax would get worn away long before any polishing happened.

            How about making female threaded pieces that you screw the bolts into?


            • #7
              Wrap the threads in electrical tape. Unless the media is really aggressive, it will work. Big question is what media? Walnut is no problem. I run a taped up container in walnut and corn for hours when moly coating bullets.


              • #8
                There are rubber/rubbery-plastic plugs that you can buy.


                When I had to acid-dip/tumble parts at Ssspinco (not a typo!) we used these folks for caps. Look under "vinyl products."
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                • #9
                  Ooooh I think the caplugs are just what I'm looking for. Thanks!


                  • #10
                    So I've found that I need to hit the threads with a little scotch brite to smooth out the crests. Could I accomplish the same thing by leaving the threads exposed when polishing with walnut an rouge or would this take down the threads too much? I've never used vibratory polishing but I'm looking for some way to cut down on manual labor.


                    • #11
                      12" rod with a threaded end to screw the bolt or screw into to protect the threads and hold the bolt for polishing.


                      • #12
                        I using walnut shell I don't believe you will need to protect the threads. If unsure throw a few in the tumbler and let it rock and roll for a few hours. Might save yourself a lot of extra work..


                        • #13
                          What do you mean by "polish"?

                          How rough are the parts to begin with?

                          I do alot of tumbling of brass castings with good detail, and also brass machined parts. All for eventual plating, which hides absolutely nothing.

                          You will find that you probably will be using somewhere between 2 and 4 types of media, depending on how rough it is to start and how fine a finish you need. I use a medium plastic media, followed by a fine, and then finally a polish called Shell Sheen, which is kinda like walnut shell. I should burnish after that, but many times don't have the time to do so.

                          With my parts, I don't worry about the threads at all. I've never had a problem, but I don't start with a real abrasive media.

                          Plasti-dip would certainly work, but could be a pain getting off, same with wax. Tape might work if you could get it to stick through out the cycle.

                          If your starting with walnut shell, I wouldn't worry about the threads unless you are tumbling them for a week (literally), which is an indication that you aren't using aggressive enough media.

                          If you have steel parts with a machine finish, I doubt that walnut shell (by itself) will do much for you. Walnut is really a polish, it's not really a remove material media.


                          • #14
                            I'm finishing 6061 with a "good" machined finish. I'm looking into those plastic caps to protect the threads from the coarse tumbling. Guessing I'll need three stages of media. I level of "polish" I need on the threads would be equivalent to holding a patch of red scotchbrite on them for a few seconds while on the lathe.

                            For the coarse I'm looking for the equivalent of a medium sand blast, and for the fine...a high polish. I don't have actual surface finish specs. I'm doing some flashlights and want the bodies to come out matte and the heads to come out polished. Can I do this in 3 stages? I'm thinking the bodies go in the coarse tumbler and the finish on the heads is probably good enough to skip the coarse and just do the last two steps. Thoughts or recommendations on media types grades? Thanks for the suggestions so far!


                            • #15
                              Piece of shrink tube?