hybrid PTFE/wood insulator

This is an experimental insulator made of wood with a PTFE insert. This was inspired by a suggestion I saw somewhere (can't find it now) that wood would be a better insulator than PTFE.

It's made from a section of 5/8" dowel (should be hard wood, the one I had was a bit soft). I drilled a 5mm hole all the way down the center, then turned an M6 bolt into the hole to thread it. Attempts to use an M6 tap left threads that were too weak. I then took a piece of 1/4" OD, 1/8" ID teflon tubing (the