I've never drilled a scale before [but I'm thinking about it with my ivories], and I'm having trouble picturing the problem. Do you mean having a washer on the outside of the scale? To stop the drill bit from damaging the ivory if it skips off the pin? (I guess a drill press is best, huh?)
Could you drill a hole the diameter of the pin through a small piece of sheet metal [or find an appropriate size washer], then tape the "washer" so it fits down over/around the pin? Then they'll be a washer for protection, right?
I'm just brainstorming without a clear picture, so forgive me if I sound silly.
Thanks,
Christopher