TapDrillSizesChart.pdf

CUT TAP NOTE: At times, you can drill a slightly larger hole to make the tapping process a bit easier. This can be done without sacrificing much of the thread’s strength. This is because most of a thread’s strength is found at its base. By making the hole larger, you are essentially cutting off the tip of a thread, not its base. You are also lowering the amount of resistance encountered while cutting the thread. This is a trick that some machinists use when they are concerned about breaking a tap tool in a hole, lowering the horsepower (HP) requirement for a self-reversing tap head or automatic tapping machine such as a Control Feed Tapper or Lead Screw tap machine.