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Tap Drill Size Calculator – Kennametal
These calculations are based upon theoretical values and are only intended for planning purposes. Actual results will vary. No responsibility from Kennametal is assumed.
Suggested Percentages of Full Thread in Tapped Holes
A common internal thread, drilled so that it results in 50% of full thread will break the external thread, before the internal thread will strip. A common internal thread drilled out so that it contains 100% of full thread is only 5% stronger than a 75% height of thread, yet it requires 3 times the power to tap.