# How much weight can a bolt take before the threads pull out?

## Main Question or Discussion Point

Hi All,
I was browsing the internet and came across this forum, I was thinking to myself one day and decided to do a google search.
My question is basically, how do I determine how much weight a bolt can take before it pulls out of the thread.

For example, I want to attach Part A to Part B with bolts and I am trying to determine the proper size. I am sure there is a formula that will tell me how much weight a bolt can take based on what material it is threaded in to, but I cant seem to find it.
I have my machinists handbook out but am having no luck, a point in the right direction would be much appreciated. I also have an old physics book and even if you could point me to the section of the book that deals with this concept, that would be appreciated also.

Thanks
Rich

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Mech_Engineer
Gold Member
Generally to determine pull out strength of a thread you will basically calculate the shear area (pi * shear diameter * length of engagement), and multiply by the shear strength of the softer component in the bolted joint.