Just google hole finders,


I have been using these in general aviation for over thirty years, and now a set like these are inexpensive to buy at Northern, for like $30.00 bucks or so and are very handy to have in any shop. The standard sizes are like a # 40, # 30" # 21 # 10 # and 1/4" per set, just drop the pin in the blind hole and drill your hole on the surface. Just google hole finders.

http://www.northerntool.com/images/p..._2000x2000.jpg

Bob