Interference studs

[EngJW]

I started to design a new stud and picked a thread out of our standards book that has an oversize pitch diameter. I don't know if it was designed to any kind of standard, although sometimes a Class 4 is mentioned.

Then I looked at the Class 5 threads in Machinery's Handbook. The question I have is do you have to apply Class 5 to both internal and external, or can you have Class 5 on the stud and Class 2 or 3 in the tapped hole?

I understand that you can check the stud threads by pitch diameter, but you need a gage for the tapped hole. Our shop is not going to be willing to buy more thread gages, so I might have to resort to using our old standard and be done with it.

Thanks for any enlightenment.

 

[Screwman]

Check out ASME B1.12 for all the info. Youwill want to use class 5 for both threads in order to have some sort of control over the installation torque. Otherwise you will have a huge spread in torque.
Please drive to a set height, and don't bottom the parts out on a shoulder.
One alternative would be to use a regular class 2 - 3 thread and fix the studs using a high strength thread adhesive. This is a good fix if the parts will not see temperature over about 350 degrees.