/diy/ - Do It Yourself

I've got a project that involves cutting lots of 1" dia holes in 1.5" thick sheets of Styrofoam. The little particles get everywhere. Here are the things I've tried:

Making a punchout tool out of some copper pipe I had laying around. Works OK but the holes are ragged and foam crumbs get everywhere. Making a hot knife out of a wood burning tool I got at goodwill and some stripped solid core electrical wire. Works OK but it's slow as hell. Making a melting tool using a small section of the pipe heated with a torch. Works great but the heat is hard to control and leads to overheating which makes the holes too big. Hot knife v2 using a circular bit I made out of the pipe (pic related) and attached to the wood burner. Slow even when I drive the wood burner with a Variac at 140V but works best out of everything. I tinned the connection with solder to help heat transfer.

Any other ideas? Wood burner is 23W, I know a bigger heater would help. Would it help or hurt to cut more material off the tool I have now?