3A capscrew with a 2B nut or hole?

[homebrewdude]

I am trying to see if this is an acceptable combination?

Class 3A has a tighter tolerance then a class 2A.
But is the 3A tolerance always within a 2B?

Is this acceptable attachment?
Or should I force my customers to use a 2A bolt with a 2B nut.

 

[BillPSU]

The unified screw system allows any combination from a 1A external thread to a 3B internal thread to screw together. The user must be aware that the fit between the different parts will vary with the tolerance the parts are manufactured to. Whichever is the lowest numbered part will control the fit. Using a 3A thread with a 2B nut will basicly end up with class 2 fits between the parts. It may cost a little more but would not cause me any concern unless you are guaranteeing something about the bolts.

 

[Heckler]

According to the machinerys handbook: Class 2A There may be fariations in thickness and symmetry of coating resulting from commerical processes but after plating the threads should be accepted by a basic Class 3A size GO-gauge and a Class 2A gauge as a NOT-GO gauge. I would also check ASME B1.1-1989