Polybushes

[Reckless Rat]

It has been suggested, reading articles on line that freezing polybar can make it harder and thus easier to machine. However they are talking about using liquid nitrogen not just bunging it in a domestic freezer. This is in particular relative to lower shore hardness than 90. I doubt if chilled poly bar out of the freezer would remain cold for long by the time you have set it up ready in the lathe. I have found it easy enough to machine as long as you give it a rest from time to time.

I will post a close up of the tool I ground specially to do the turning tomorrow once I get back down to the garage. I also made a very thin parting tool to start off the parting process, which I finished using a hacksaw.

I found drilling/boring the poly bar was easier using an end milling tool rather than a twist drill.

Another alternative is to buy the polyurethane as a raw product, mix it with the hardener and then pour it into a pre-prepared mould.