Bolt Tensioning

The correct answer is ... that depends. On the bolt, the size of the bolt and so and and so forth... I always say "Tighten the bolt until it breaks, then back it off 1/4 turn and that is the correct torque."

Ok, kidding aside. see this site. it has your answer.

http://www.engineersedge.com/torque_table_sae_ftlbs.htm

Many years ago, a group of amateurs working within the heritage railway movement dismantled and recovered some track at a cement works for use elsewhere. It was a cold January day and there was snow on the ground. One particular fishplate bolt and nut, with a 15/16" BSW thread, was rather stiff owing to the presence of hardened cement dropped from the vehicles passing along the track. The volunteer added a long piece of pipe to the fishplate spanner being used and applied additional torque using body weight. After some time the unscrewed nut dropped into the snow and proceeded to fizz, producing steam!

The same individual has inadvertently sheared the bolts of 7/8" BSW fishplate fasteners using the same technique...

So, you should never grab your nuts when they are steaming??

I'll try to remember that.

What type of bolt do you want to tighten, carbon steel ,stainless steel, heat threated steel , and what size. In general you get a chart from a tool supply house , select the bolt size and buy the Torque wrench . Set the wrench to the in/lbs or ft/lbs recommendet for this bolt size . Better yet read the instructions.

There are markings on the end of the bolts. Those markings tell you the grade. If there are no markings, then it should be assumed that it is an ungraded bolt. Then based upon the bolt grade and the size (assuming also that this is not for an unusual use) you can look the torque specification up in a chart. The application generally does not matter it would be the same torque for a 3/4" bolt if it were on a car or on a bridge.

Here's one with torque specs:

https://www.raskcycle.com/techtip/webdoc14.html

Some bolts are torqued to yield and are not to be reused. The marking on the head tells you that also.

There are several threads on this forum about torque. You might try "Search All of CR4" at the right side of your screen. Search for "Torque" also try other related keywords you might find some very interesting comments.