11/16 UNEF Drill size

11/16 UNEF Drill size

This topic has 8 replies, 6 voices, and was last updated 2 April 2021 at 20:30 by David Noble.

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2 April 2021 at 16:44 #537671
Jayme Gisbourne
Participant
@jaymegisbourne80009
As a young lad I am blessed with the use of 60 degree threads that are now widespread. It’s easy to work out the drill size as all you have to do it minus the pitch from the OD and you get your drill size.
I have a project at home and I need a big fine thread. I looked through my late grandfather’s tap box and found a 11/16 -24TPI tap. I’m just wondering on the tapping drill size as this seems to be a non standard thread.

Kind regards,

J.
Advert

2 April 2021 at 16:44 #28083
Jayme Gisbourne
Participant
@jaymegisbourne80009
I need to know the drill size or how to calculate it myself.
2 April 2021 at 16:50 #537674
Trevor Drabble 1
Participant
@trevordrabble1
According to my Tracy Tools wall chart that is a UNEF thread , and their recommended tapping drill is 16.25 mm dia .
2 April 2021 at 17:40 #537683
not done it yet
Participant
@notdoneityet
If you are blessed with the formula, why not just use it!

Diameter is 11/16” = 0.69” (0.6875)

Pitch is 1/24” = 0 0417 (0.04166)

Diameter – Pitch = 0.6875 – 0.04166 = 0 646”
2 April 2021 at 17:49 #537685
DC31k
Participant
@dc31k
If you type your topic title into Google, exactly as you have written it, you will find the answer to your query.

E.g. https://www.gewinde-normen.de/en/unified-extra-fine-thread.html

It will also suggest you use a drill sized at 16.6 of those new-fangled continental millimetric units rather than the bizarre not-in-any-standard-range imperial number quoted above.
2 April 2021 at 17:59 #537690
not done it yet
Participant
@notdoneityet
For those unable to work out the metric size, 0.646 * 25.4 would provide the metric drill size.

I expect the imperial drill size could easily be provided as a fraction, if really required. Just a bit more simple maths.
2 April 2021 at 19:22 #537704
roy entwistle
Participant
@royentwistle24699
83/128ths I think

Roy
2 April 2021 at 19:41 #537707
Jayme Gisbourne
Participant
@jaymegisbourne80009
Posted by Trevor Drabble on 02/04/2021 16:50:49:

According to my Tracy Tools wall chart that is a UNEF thread , and their recommended tapping drill is 16.25 mm dia .

That’s great thank you!
2 April 2021 at 20:30 #537716
David Noble
Participant
@davidnoble71990
Posted by roy entwistle on 02/04/2021 19:22:31:

83/128ths I think

Roy

David
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