Can we put GD&T on Thereads?

[msbharaj]

I have to add a perpendicularity condition on a threaded hole in oone of the parts. I have not put the GD&T on the threaded parts. Is it possible to do it.

 

[TheTick]

To the best of my knowledge...
GDT applied to threads applies to the pitch diameter of the threads unless otherwise specified.

 

[CoryPad]

Yes, it is possible to do this. [blue]TheTick[/blue] is correct that the pitch diameter is default. It can be difficult to check GD&T using pitch diameter, so you can specify the minor diameter for internal threads and the major diameter for external threads to simplify things.

For example, let's assume you want the tapped hole threads of a boss to be perpendicular to the boss face. Specify the boss face as datum A. Then, use an arrow pointing to the internal threads, use a text note saying minor diameter, and use GD&T symbols for perpendicularity, the allowable tolerance, and refer to datum A.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[msbharaj]

yes, as per my knowledge it is applied to the root diameter of the threaded shaft or hole. But in the drawing we specify the thread information only. So how can we ensure that threaded hole or shaft is perpendicular or concentric to a particluar datum.

 

[type26owner]

That would be a fixed fastener situation. One would specify it with positional or orientation controls normally. Since a fixed fastener feature presumably aligns something like a dowel pin or a threaded fastener then relying on the virtual condition boundary of that feature does not ensure the assembly will go together. To do that the fixed fastener feature must align to the virtual condition boundary of the adjacient mating feature in the other part which most likely is a hole. This fixed fastener problem is solved by specifying a projected tolerance zone. This message is to point you in the right direction only.

 

[arto]

Also, you may want to give a projected tolerance zone on position, equal to the thickness of the mating part, if you have a bolt pattern.

i.e., if you have a pipe flange mounting with tapped holes, you want the bolts to be able to go through the flange back surface. [You don't just want the tapped hole pattern correct, but the tapped hole axes straight enough.]