What are bolt grades?
We frequently see questions regarding bolt grades, so here’s a partial list. Please note that just because a bolt is grade 2 does not mean it will break easily. Grading only refers to the minimum strength, not the maximum. Thus, if a machine uses a soft bolt as a safety shear pin, and you happen to replace it with a grade 2 bolt that was actually manufactured to grade 8 specs (but was marked down because too many of the bolts in the lot failed, so the whole lot was marked down) you could create some serious problems. Replace safety-related items with proper stuff! Also beware of improperly-marked forgeries. If your application is critical, test some samples or get certified hardware (not that readers of rec.crafts.metalworking are likely to be building interstate bridges or spacecraft, but it’s worth saying). A note on “strength” which is actually a complex subject. First, note that there is a maximum “dry” tightening torque, and that part of this torque goes to overcoming friction. Th
