Drill sizes for metric tapping
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From: Carl <carl.blum@...>
Sent: Tuesday, September 5, 2023 12:49 PM
To: [email protected] <[email protected]>; calciu1@... <calciu1@...>
Subject: Re: [Unimat] end mill holder
?
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:
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.)?
