Hello:
I was
told tap drills in metric are simple: screw size minus pitch,
so M14 - 1mm = 13mm tap drill. 12.75 might be 100% thread, but
not much stronger than 75%.
Carl.
On 9/5/2023 12:05 PM, Andrei wrote:
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12.75 is the drill size for an M14 tap
I got one with a 8mm
hole, ER-11, IIRC, with the intent to thread it M12x1 for
my SL/DB machines. It's here somewhere! ;) IIRC, M14x1
needs a 13mm tap drill? I have a pair of very nice
tungsten carbide 11mm tap drills for my M12x1 stuff. Works
nicely on hardened steel, which most of those things are.
For my ER-25 Collet holder that I "made" from one of the
longer shank collet chucks, that was a hard skin, but the
tap had no problem once the tapping hole was drilled. Made
it pretty easy.?
Bill in OKC
William R.
Meyers, MSgt, USAF(Ret.)?