Get with this 3 piece drill gauge set. These steel plates have realise markings, precision sealed gauge holes and lists -LRB- 1-60 -RRB-, lettered -LRB- A-Z -RRB- and three-quarter -LRB- 1/16-Inch - 1/2-Inch by 1/64-Inch -RRB- sized drill bits. guessing and check those drill sizes before you drill that hole. Even a tap drill/clearance drill reference chart.