Is the shrinkage enough to worry about?

It is if you want something like a bolt to run through it unless you go over size in the first place...have a play is the best answer really and see for yourself how nutty the stuff is:)

Dont worry about him he,s just an old fart. :p
he probably thinks we are talking about teflon ...lol
loads and loads of our plant use modern day plastics like delrin as bushes for pedals and linkages etc and they are out in the sh@t and elements all the time, modern plastics are a bit more stable nowadays.
so use a good quality one.
As for the pivotif you are going to use a bolt use a shouldered bolt so the delrin is not running on threads.
cheers les g

As it happens I`m about to make thebushes for my pedals although mine are top hung. I`ve opted for simple nylon to make them from as it is cheap, hard wearing and with top mounted pedals easily replacedif needs be.

D.

Acetal is bonkers. I spent hours machining stuff when I worked for a motorsport firm at Silverstone only to find the holes I bopped up the spout were undersized yet I used the right drill bit...it seems the speed of the machine and how quick you bop the holes has an affect as well as I never had one hole that was the same.......freaked me out, it was as if some ghostie type changed the drill bit each time i used it.

Facing off a rectangle of acetal in 3 jaw chuck was just as frustrating...:D

its just because its soft and flexible think of trying to drill a hole in a block of rubber :confused:

you really should be locked up.....for your own safety......lol
you,ll be using four jaw chucks and trying to self center hex bar next :D
slow and steady wins the race
proper center to start
nice sharp new drill bit nice and slow and all is well
and a reamer helps as well
if you go at it to fast it can pull off centre
cheers les g

All depends how hard you pedal, some go steady some go hell for leather:)