Well that wasn't a great success, all I have is larger than your 3mm. I tried turning some nylon down & it's not consistent, a bit like a potter trying to throw jelly. I've some more perspex in the garage which will turn & some tufnol, trouble is the car's in there with no way to shift it at the moment,
I guess I'll have some scroll pins of the correct diameter, whether they are long enough I don't know. I'll look later.
M