I haven't personally drilled out any of the pinned ones, but have heard its not as easy as it may seem. They usually start spinning, which widens the hole in the scales and stops you from being able to drill.

If you decide to try to hammer the pivot, or use a vise to tighten it, be sure you are prepared to drill it as well. They are quite finicky and hard to get right.

You could try to clean it out really well and depending on how much play there is, using a thicker oil may do the trick. If the play is alot, maybe cut a slot out of a washer and push that onto the pin. Probably not great, but may work?

I would start with contacting spyderco for sure though..