Made my PTFE (Teflon) gudgeon buttons this evening. They came up quite good. I made them in matching sets for each individual gudgeon because they aren't all identical lengths, it probably wouldn't have mattered but it didn't cost me anything to get the exact length i wanted.
I've given them .5mm float in the bore and the radius is smaller than the rad of the piston so that there will be only single point contact in the centre. PTFE is very dimensionally stable above 23 degrees so there should be no trouble with thermal growth.
On to pics so you can so what i'm ranting about..
Here's a piston assembled with the pin and the buttons in..
And here's what the buttons look like.. Sorry, the pic is a little blurry.
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