Thread stress calculation for aluminum material 6061-T6 2

[1623]

I need help on thread stress calculation for aluminum 6061-T6. The thread size is 6-32. The mating screw is stainless steel material. The torque apply to the screw is 7in-lbs. Is any one has the formula I can use to do this calculation? I want to know if 7in-lbs torque is too much or noT for the 6061-T6. Thanks.

 

[CoryPad]

The information in faq725-536 and thread725-35222 can be used for the calculations you require. You will need to convert your inch-pound units to SI equivalents.

Cory

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

 

[Cockroach]

I'm finding that your torque value, 7 lbf in, is acceptable, however you only have a Factor of Safety of 1.05, worst case scenario.

Your stress is approximately 22.3 ksi at the pitch diameter of the pin. This is acceptable for stainless steel but marginal for Aluminum 6061 Grade T6, rated at 23.3 ksi in shear. (Alcan listing, normal stress of 35 ksi)

I have found another listing for the material which gives a slightly higher value for normal stress, 41 ksi, hence I would exercise caution when applying the load(s).

Hope this helps you out.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[1623]

Hi Kenneth,

Thank you for your feedback. I am just wondering if you can point out to me that where I can get some help on the calculation. Maybe a little software I can download or some kind of spreadsheet I can plug the number in. Thanks again.

 

[Cockroach]

Good Morning "1623"

Yeah, I can send you an Excel file for the threading calculations, several have been handed out already in this forum. This will assist you with the threading geometry and fracture mechanics calculations associated with Acme, Stub Acme and Unified National forms.

As for the actual calculation, there is no real set way to approach a computation. What I can do is summarize the calculation in MSWord and send you that file also.

If you e-mail me direct at "kenny.hueston@nuflotech.com" I will get back to you through your return address.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada