vinyl slugs are softer, drill very well, but they are affected by the pigment put in them to make the colors. The darker the color, the harder they are to get smooth. When you do get them smooth though, vinyl slugs are very slick. I wipe them down with some acetone after drilling, this melts the vinyl slightly and makes them slick. A little soapstone helps too, very slick!!!
Urethane slugs are a harder material, same feel color to color. You can get these very smooth too, put a piece of scotch brite on your sander instead of sand paper, verrrrry nice!
Urethane is the way to go !!!
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Mike Austin's Precision Pro Shop
Houston, TX
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