Pull-Out Force (lbs) in 6061 T6?

[jgwis]

I am a New member to eng-tips.com and would appreciate your help in determining pull-out lbs for the specifications below.

I spent the past week trying to find a good formula / calculator for Pull-out force in aluminum with a SS bolt.

My Situation: 1/4-20 SS fastener in 6061 T6 Aluminum. Recommended Engagement .612"

I am able to calculate Internal and External Shear Areas for Threads and Minimum Thread Engagement; however, I am unable to calculate Pull-Out in lbs.

One formula I came across:
Pnot = 0.85 (Te)(D)(Ftu2)
Te = length of thread engagement
D = nominal screw diameter
Ftu2 = tensile ultimate strength

3124 = .85 (.612741) (.250) (24,000psi)

3124 seems way too high of a number for a 1/4-20 in .61" aluminum...

Am I missing something?

Thanks,

Jim

 

[CoryPad]

This thread contains the equation (in SI units) for calculating thread stripping.

thread725-35222

Regards,

Cory

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