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Thread: Are Perfect Circles Achievable? Any tips on cutting Polypropylene

  1. #21
    Join Date
    Oct 2000
    Atlanta GA


    I made a trammel gauge out of a piece of wood, a drill bit, and a pencil. Take a strip of scrap wood maybe 1" x 1" x 20" long. Drill a hole in one end just large enough to snugly stick a pencil into. Wrap some masking tape around the pencil if needed for a snug fit. Drill a hole in the other end with a 1/2" drill bit. Now jam the drill end of the bit into the hole, and chuck the shank of the 1/2" bit into the router. The pencil should be at the other end of the stick, pointing down towards the table.

    Of course the router is never turned on during this entire process. By making a larger diameter trammel you do not need micrometer accuracy. If you can adjust your Z axis to get the pencil tip to vary from the surface no more than 1/16" over a 36" diameter circle, that will equate to less than .002" with a 1" diameter router bit.

    The pencil and drill bit are still usable, so the only cost is the strip of scrap wood.

    You can make a decent surfacing file by drawing a rectangle a little larger than your table in PartWorks, and using a Pocketing toolpath with Raster selected instead of Offset. With a back and forth cutting action you may still see stripes even with almost perfect smoothness due to the opposing cut directions of the alternating stripes.

  2. #22
    Join Date
    Mar 2011

    Default Pvc

    Found some good info on PVC at They have data sheets and whole bunch of stuff that might help.

  3. #23
    Join Date
    Mar 2004
    Delray Beach, FL


    A botter in Canada (Paco) wrote a surfacing program for hardwoods and surfacing your table that works well. Here's a link to it:

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