View Full Version : D-7 spec on Metric tap?

06-06-2008, 11:15 PM
On a 14x2 metric tap there is a D-7 specification, I have seen H3,4,5 etc but not D7, is that the same as H# but for use with metric?


06-06-2008, 11:50 PM
I dont know that spec but any tapped hole that has specs I would use a roll tap. they are stronger and tap a better hole to start with.

Screw machines use them and tap good holes faster than any cutting tap ever will.

form/roll taps rule...

06-06-2008, 11:58 PM
I agree on the form tap, these holes do not have a spec, I bought these high quality taps very reasonable and was just curious as to what the D-7 designated.
Probably why they were so reasonable :D

06-07-2008, 12:04 AM
Cool when you get an answer I will learn too. Metric tap specs are beyond what I know but I do know roll taps are best for holes with specs.

Im here to learn too. ;)

06-07-2008, 12:17 AM

Yep, D numbers are the metric worlds way of tap thread limits.

An M14 x 2 - D7 should have a pitch dia of 12.751 min / 12.792 max

Its pretty close to what you guys would know as a 6H fit. And thatís fairly standard for that size.

Regards Phil.

06-07-2008, 05:05 AM
These might help. There isn't a lot about.





06-07-2008, 08:50 AM
Thank you for that Phil, good to know that D-7 is pretty much standard.

Oldtiffe, thanks for the links, it was surprising how little, read nothing, that I found searching.


06-07-2008, 03:41 PM
Ken - Is it a Form-tap or a cutting tap? Forming taps come with something like 6HX tol.. A cutting tap M14 x 2 - 7D would be a special oversize M14 +50/+68.
(Tap tol. are designated with the number first and than the letter like in 3H etc.). Do not confuse this with class. In ISO you also have class 1 or 2 or 3 etc.
Pitch dia for M14 x 2 is 12.701 add 7D tol. +50 /+68 and you come up with
12.751/12.769 .
Formula for theoretical pitch d2 = d - 0.64952p
For the inch crowd - that is approx. 0.002 - 0.003 inch oversize.
Wow!! Time for a beer.

06-07-2008, 07:44 PM
It is a cut tap juergenwt,

This is the exact text;
7336 HS
2552 G D7

06-07-2008, 08:37 PM
McMasters list this as the "Ground Thread Limits" for Metric taps, so Phil you are correct, so was I but mine was a guess :D

They listed two for the M14X2, D3 and D7 so looks like it is as mentioned a pretty standard tap.

They did not list what the limits were, juergenwt, I bet your calculations are more then close enough for Government work.