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 same recommended for a bowden extruder, in fact I just cut an extra piece off of mine) and turned an M6 nut up and down the tube a couple of times. The tube is too flexible for a die to thread it cleanly, but you get pretty good threads with a nut.

I screwed the PTFE into one end of the wood and the heater barrel into the other until they pressed against each other, then cut off the excess PTFE and drilled it back out to 1/8" (screwing it into something constricts it). I finished it off with a countersink bit to widen the opening.

This all really should have been done with a lathe or at least a drill press, but I only had a power drill, so my hole wasn't perfectly centered or vertical. My extruder is broken, so I can't test it until some new parts arrive, but it seems smooth and solid. If wood really is a better insulator than PTFE/PEEK, this may be a viable alternative, and the material costs should be lower than existing insulators.