Originally Posted by
LordFoo
Sheldon Brown comes through once again:
See "
Mounting recessed calipers on older frames". I did this on my old road bike and it was quite easy -- as Sheldon says on that webpage, drilling to expand an existing hole is super-easy.
use plenty of "CUTTING FLUID" ( at hardware store) when you drill, clear the shards often, and try VERY hard to keep the drill square to the hole (jig or use a drill press)
OBVIOUSLY you want a BRAND NEW SHARP CARBIDE (or TiN coated) BIT made for cutting metal (NOT the 10 year old bit that came with your ryobi)
use a countersink bit on slow speed after to slightly chamfer the edges of the hole for professionalism.