Our Tap Drill Reference Table is a must have for any toolmaker, machinist or mechanic. The double-sided guide features a Tap Drill Depth Chart, decimal conversions from 1/64 to 63/64 and a ruler graduated in 64ths. The Tap Drill Reference Table works with National Fine, National Course, American Standard Pipe and Metric threads. Essential reference guide for toolmakers and machinists. Front side has machine screw Tap Drill Chart for recommended 75 percent depth. Back side has decimal equivalents table in 64ths from 1/64 to 63/64 in. 6 in. rule with 1/64 in. graduations. For National Fine, National Course, American Standard Pipe and Metric threads.