I need thread sizing help

[AGCB97]

I have a external thread that measures 1.992 (18 TPI) so that should be a 2.012 nominal size (.99% of nominal). I need to make a nut to fit it. It is standard 60 degree thread.

I assume that the bore for the nut should be the same as the nominal size (2.012).

Am I right in this?

This is an odd ball size, I know but size shouldn't matter if the right relationships are maintained.

Thanks for your input
Aaron

 

[mickri]

As I understand your post you have a 1.992 OD with 18 TPI. The bore on the nut has to have an ID smaller than the OD. The bore needs to the minor diameter of the thread. According to the thread calculator that I use the minor diameter range is 1.9092 to 1.9240 This is the thread calculator that I use for odd ball threads. UN imperial screw thread calculator (theoreticalmachinist.com)

 

[Flyinfool]

If you bore the nut at 2.012 it will be a nice slip fit over the thread.

Thread sizes are always based on the major dia of the internal thread, That is why a bolt always measures smaller than the nominal size, it has to be smaller than the nut to fit inside of it.

The Major Dia tolerance for a 2.000-18UNS -2A thread is 1.9985 / 1.9897. Your 1.992 is right smack in the middle of that tolerance. So I am betting you have a 2.000 inch thread.

For the mating nut with a 2.000-18UNS-2B thread the minor dia or bore size would be 1.9525 / 1.9399.

 

[SLK001]

What mickri said. If you bore the nut to the nominal size, you'll just have a bushing.

 

[AGCB97]

OK, yes I forgot to subtract 2 x the tread depth = .072
So then it comes to 1.940
I think the difference between your calc and mine is the clearance

 

[Flyinfool]

I still think you have a "standard" 2.0000-18UNS-2A thread.

 

[MrWhoopee]

I'm with @Flyinfool, its a 2.00-18 UNS thread.