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Nylon Screw: Fine or Coarse Thread?

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  • Nylon Screw: Fine or Coarse Thread?

    Hi everyone,

    I'm Building a Biesemeyer style table saw fence that will have 1"x 2"x 1/8" UHMWPE or HDPE pads for sliding across the rail and table top.

    I'm thinking about attaching the pads to the 1/4" thick steel with countersunk 10-32 or 10-24 nylon screws, but can't decide which would be better in this application.

    Which would you use?

    Thanks,

    -- Bill
    Last edited by cryptrx; 02-14-2012, 09:48 PM.

  • #2
    The ones I already had, or the ones easier to get, or the cheaper of the two....

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    • #3
      I think I've read a few times in the past that coarse threads work better for plastic.

      John

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      • #4
        If tapping for either of the screw sizes you mentioned, use a quality HSS tap. That way, you'll have nice crisp threads!

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        • #5
          Show pics of this project.......I got a nice Delta cabinet saw and lent it to my father as I'm out of room and he managed to break the fence the first time out.......must be payback for my mispent youth........LOL He's got to do better than that........
          Opportunity knocks once, temptation leans on the doorbell.....

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          • #6
            I'd use steel ones and be sure to csk deep enough to be well below
            the surface. Socket flat head screws are the best. :-)
            ,,,lew,,,

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            • #7
              I'd use steel screws as well. If you have to, you can grind some material off the flat head- you won't be making the screw all that tight anyway, or you'll probably warp the uhmw. If the screwdriver bit goes into a hole that's only half as high as it used to be, that will be fine. I would use a robertson head screw- it's pretty hard to grind away from a slotted or philips head and still be able to get some torque on it without the bit slipping.

              If you can get an allen head screw, that would work also if you need to reduce the height of the head.

              You're not using the screws to keep the plastic tight to the metal, you're using them to keep the plastic in position, so you mainly need to keep the screws from backing out. 1/8 inch thickness of plastic isn't much, or I'd recommend button head screws instead. You'd recess the material so the head can sit deeper than the surface of the plastic, and the recess would have a flat bottom. In most cases, this would be better for holding plastic to another surface.

              Of course, you can always countersink into the steel a little, so with your countersink screws you can leave the heads alone and they could still be made to go 'under flush'. You have 1/4 inch of steel- if all you were left with was 1/8 inch of threads, that's still more than enough in this application.

              If there's going to be any part of the screw threads exposed where clothing and skin could catch on it, you would probably want to cut the screws short enough so they don't stick out. The less stuff to catch things on around a table saw (and many other machines) the better.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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              • #8
                You definitely want coarse threads since they will have less of a tendency to cross thread or pull material out when you tighten them.

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