You normally would not use a reamer on a tang hole. Just use the next size drill. Keep in mind g10 or micarta will shrink back a few thou when drilled and metal does not. What I mean is usually a 1/8” drill will make the hole oversized enough (in metal) to allow a 1/8” pin (Corby, etc) to fit but that same 1/8” drill will make a slightly undersized hole in g10 or micarta and some wood. Micarta will “shrink” back after drilling.
Your pin should move fairly freely in scale material. If you have to pound your pin into the scales during glue up, the holes are way too small and the handle material will eventually crack.