Bolt Minimum Thread Engagement

[logokster]

I have a 3/4"-10 A325 bolt that is approximately 1 thread short in the nut. Assume 9 threads are engaged and the materials are of the same strength, how do I calculate the absolute minimum thread engagement such that the bolt still controls and will exceed allowable in tension prior to the bolt/nut threads exceeding the allowable in shear. One idea I have is to calculate the maximum allowable tension in the bolt (Using ASD, F(lb) = 0.33 x Fult x Aten) versus the shear strength of the bolt (Using Federal Highway H28 to calculation Asa and ASD for allowable shear load, F (lb) = 0.4 x Fult x Asa = 0.4 x Fult x pi x E x Le x 0.75). Then set these equations equal to each other. All values are known with the exception of Le so I would be able to determine the minimum thread engagement required in the nut such that the bolt still controls.

Let me know your thoughts. Thanks.

 

[desertfox]

Hi
Try this

http://www.engineersedge.com/thread_strength/thread_minimum_length_engagement.htm