UNS Threads Dill Size

[teccboxx]

I cannot find the recommended drill size for a 1"-32 UNS tap. Check all over google and my machinery's handbook. Any chance anyone know how to find this?????

Or the specs of the thread so I can calculate it.



EDIT*************

Well I just found my answer, 31/32"

[ad64075]

To calculate tap drill sizes for inch threads, use the following formula:


TD = M - ((1.08253 * P) / TPI)

When M = major dia
P = percent full thread (in decimal form)
TPI = threads per inch

So for your 1"-32 tap assuming 60% threads, your hole size would figure to .9763. Wow. Sounds big, eh? Go up to 100% threads for a .9662 hole size.


This formula will work for ALL inch threads.






There is a similar formula for metric threads:

TD = M - (1.08253 * P * TP)

When M = major dia
P = percent full thread (in decimal form)
TP = thread pitch




Hope this helps!!!

[beege]

Check out Michael Rainey's Close Tolerance Software, and pick up "ThreadPal". You can input any oddball thread, and it will give you what you need, including tolerances, thread wire info.

[fizzissist]

All that math has my head spinning.....

If you forget the formula, can't find it, or you're in a pinch...keep in mind the principles.

In this case, you've got a 32 pitch thread, and it's UN series. Take a standard size you know, like 10-32, and use the difference between the nominal and the tap drill for that size to get the difference for your size.

A .188 nominal, minus the .159 tap drill (#21) for 75% gives you a difference of .029 and if you subtract .029 from the 1., you'll get a tap drill size of .971 and for a 50% thread it's .981

The thread form remains the same, no matter the diameter.

[juergenwt]

Just take the major dia. and subtract the pitch.