I’d like to put a circular high strength shaft insert into a metal 12-tooth gear, but the gears have beveled corners and the inserts do not, causing them to not fit. Is it allowed to sand the corners so that they would fit into the gear properly?
Yes. However, I assume you are talking about the black/dark grey inserts. If you use the light grey ones they will fit.
They’re green, I think they might be an older version or something like that.
Yeah I have green ones too but I think those might be for screws. For shafts there should be light gray metal inserts
Rule R16 in the game manual has the answer.
The green inserts work well with normal drive shafts, and sanding off the insert edges is legal, as long as it doesn’t involve major modification like cutting it in half and gluing it back together backwards, for instance.