The proof load is the maximum load $($foree$)$ that a bolt can withstand without acquiring a

permanent set. When no bolt grade or specification is avallable, the proof load for a bolt

with yield strength $S_y$ and area of threaded portion $(A_2)$ is:

$($a$)0\mathrm{.}75A_t{S}_y$

$($b$)0\mathrm{.}85A_t{S}_y$

$($c$)0\mathrm{.}90A_1{S}_y$

$($d$)0\mathrm{.}95A_t{S}_y$