I have a question on two terms used in defining a new thread.

Thread Minor Diameter and Thread Minor Diameter Inside

The data for a 1/4-20 from the hole wizard data:

Thread Minor Diameter; = 0.1905

Thread Minor Diameter Inside = 0.1959

I can not find any thread data close to the numbers given above for a internal thread in any of our thread data books.

Is the Thread Minor Diameter the theoretical diameter for 100% full thread?

I just need to know exactly how the terms above relate to physical thread geometry.

And where I can find the data or what formulas are used to derive them.

The answer in S-04970: Thread Minor Diameter = the diameter of a cylinder formed by the roots of the threads

Thread Minor Diameter Inside = the diameter of a cylinder formed by the crests of an internal thread

Is unclear at best as to how the number relate to the actual thread geometry.

Even my VAR can not give me a clear answer as to exactly what Thread Minor Diameter and Thread Minor Diameter Inside are.

Mike,

I am running 2011 SP3.0 I placed a 1/4-20 hole using hole wizard

and my major was Ø.250 with a minor of Ø.201

The is in line with the machinery's handbook which says

the major is ..250 with the minor being .196 - .207

Now this can vary depending on the class.