Drilling UHMW

[Mr Ron]

I need to cut some "pucks" from 3/8" thick UHMW plastic. I need to use a hole saw to get the 4" diameter pucks I need. Is there a better way to make these pucks (fly cutter?). Is there a way to use a hole saw that won't melt the plastic? I watched a Starrett video on their new line of hole saws and they might be what I'm looking for, but I wonder about speed and feeds when cutting UHMW.

[johnfreese]

Band saw the blanks and finish in the lathe. Pressure turning is the easiest. Put a 4" steel bar in the lathe. Face it off. Glue a piece of coarse sandpaper to it, press the blank against the sandpaper using the tailstock. Take light cuts to finish the OD.

[Conrad_R_Hoffman]

I use that technique for all sorts of thin and hard to grip parts. Works great.

[Mr Ron]

Band saw the blanks and finish in the lathe. Pressure turning is the easiest. Put a 4" steel bar in the lathe. Face it off. Glue a piece of coarse sandpaper to it, press the blank against the sandpaper using the tailstock. Take light cuts to finish the OD.

WOW1 That is a great idea using coarse sandpaper. Thanks a lot.

[johnfreese]

Sometimes I just press the work against the chuck jaws. The UHMW is probably too slick for that to work. Some people face off a blank, then cut some circular grooves in the face and then attach the work to the blank with super glue. The grooves provide space for excess glue. After machining the work can be separated from the blank with heat. Unfortunately that method doesn't work with plastics.

[Mr Ron]

Sometimes I just press the work against the chuck jaws. The UHMW is probably too slick for that to work. Some people face off a blank, then cut some circular grooves in the face and then attach the work to the blank with super glue. The grooves provide space for excess glue. After machining the work can be separated from the blank with heat. Unfortunately that method doesn't work with plastics.

Thanks again John for these good ideas. This forum has some of the smartest and friendly people who share ideas with others. You don't find these in books.

[ChipMaker4130]

If accuracy is not an issue, you'll still be ahead time and fuss-wise just using a hole saw. Use the coarsest tooth one you can get and don't turn it fast and it won't be a problem. You can also flood it with coolant or even water. You will have to deal with a burr unless you cut part way through, turn the sheet over and finish from the other side. Still much faster than a bandsaw/lathe.

On UHMW that thin, the pilot drill won't hold a 4" hole-saw very stable on either the first or flip-side. Best to clamp the material down on a mill or drill press, or clamp to a 1/8" steel plate (or similar) with pre-drilled pilot hole, on the back side from your cut. The pilot drill should just about hit the steel hole by the time the saw hits the plastic. Some have adjustable-length pilot drill setups.