How would you make a 2-1/2″ hole in a piece of 3/4″ plywood? A great choice is to use the 2-1/2″ hole saw that is included in the Ridgid 7040 13 piece Bi-Metal Hole Saw Set. This is the one set you need for all your large diameter holes. Since these hole saws are not your standard steel, they are able to handle going though some pretty though materials thanks to the bi-metal construction. The whole set comes in a compact hard case that keeps everything organized.