Method to calculate material around internal threads

[Mechanimal]

Hi,

I believe this problem was raised here:

http://www.eng-tips.com/viewthread.cfm?qid=244721&page=9#post

I can't seem to post to it since it is closed. The question I have is if you decide to use the short answer method

"The short answer is to use the same number as the width across flats on a hexagonal nut of same/similar strength/size to your part."

and the yield of the material you are threading is less than the yield of a nut would you scale up the width based on the yield ratio? Example:

nut width = x
Yield nut =Sn
Yield material to tap = St
Required width =x * (Sn/St)

 

[CoryPad]

No, you would not adjust width based on strength ratio. You would adjust axial thread engagement based on strength ratio.

 

[Mechanimal]

Thanks for the reply,

The proof strength on the equivalent nut is about 90ksi, I intend to use 44ksi material. Is there anyway to calculate a minimum width for internal threads other than using VDI 2230?

 

[CoryPad]

The same information is in An Introduction to the Design and Behavior of Bolted Joints by Bickford. The original research was published by SAE International as part of their Technical Paper series: Alexander, E.M.: Analysis and design of threaded assemblies. International Automotive Engineering Congress and Exposition Detroit (1977), Report Number 770420.