huangyhg

tension bolts - thread projection past the nut
there is no thread "stick through" or run-out requirement past the face of the nut. full engagement of the threads is required. see aisc requirements for high strength, bolted connections.
i agree with ron, although i have heard "rules of thumb" in the past. it doesn't take much to see that the idea is entirely subjective though... one such rule was that the threaded end should protrude at least a 1/4" from the outside of the nut. and it will and maybe it won't depending on who calculated the lengths.
aisc states "the length of bolts shall be such that the end of the bolt will be flush with the face of the nut when properly installed".
q is right...old rule of thumb of 1/4 inch or so. this was primarily for visual inspection purposes to make sure you got at least the full engagement of the threads and to be able to see such at a distance.
ron
i agree with q and ron that there is no particular requirement. i suspect that the bolts and nuts have been designed on the assumption that the thread stops flush at the face. however, the south african institute of steel construction handbook does specify that after installation there should be at least one complete thread on either side of the nut.
carl bauer
i'm not aware of any requirements for projection past the nut.
with respect to the south african requirements, aerospace requirements are that there are two threads exposed on the tension side of the bolt where most other bolt specs require that there are 6 threads for tensile testing. testing values indicate that having the two threads increases the tensile capacity by approximately 10%. i'm not sure about the reason for the increase except that there could be funny stress risers in the vicinity of the threads and that with the thread generally being the weakest part of the bolt that the 6 threads provides a greater opportunity for failure.

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