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- Dec 27, 2014
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a 3/8-16 tap drill would be 5/16.
True, if you want 100% thread contact. It might be hard to thread the two together, though. 60 to 75% is norm, depending on material and usage.
a 3/8-16 tap drill would be 5/16.
Not really, this generally yields a 75% thread, also the question is about taps where the size is fixed by the tool, the Pitch Diameter of taps are not easily changed.True, if you want 100% thread contact. It might be hard to thread the two together, though. 60 to 75% is norm, depending on material and usage.
the Pitch Diameter of taps is not easily changed.
I have no idea why I remember this, in order to determine the Major Diameter of a number sized screw thread multiply the number by .013 then add .060, whoever thought this was a good idea in 1870 something deserves to be forgotten.My Starrett card does say 5/16 is the tap drill for 3/8 16. Hmm.