Standard DTI FAQs > Bolt Torque requirements

Torque requirements

1. How much torque does it take to tighten a bolt?
   
   
2. You need a recommendation for tool size and capacity to properly install your bolts and DTI's See tool capacity
   
   
3. How much torque does it take to tension a bolt with a DTI See torque control

Because torque at specific bolt tension varies by as much as +/-30%, even within a specific set set or lot of bolts, Torque tables are not allowed for structural bolts. If a torque value is to be established for a particular bolt grade and diameter, the Research Council rules are as follows:

1. Select a representative bolts/nut/washer set. Be sure to duplicate the condition of the bolt set, that is, weathered, rusted, new, long, short, etc.
2. Tighten it in a Skidmore to 1.05 times the minimum tension required (see bolt tension).
3. Do this three times. Average the results.
4. This torque value becomes the value to use for that shift, for that type of bolt set and condition. Remember, if any of the hardware or tightening conditions change, the torque setting must be recalibrated. Calibration of torque must be done every day without fail, or more often.

If you would just like to estimate the torque (say, to pick a wrench capacity), a guestimated torque value can be determined from the simplified formula

Torque = Tension x (nut factor) x (diameter)

where Tension is probably that listed in table bolt tension, or some other value established by the engineer-of-record,(nut factor) is some number between 0.12 for brand new well-lubricated bolts and 0.20 for dried out or rusty bolts, and (diameter) is the diameter of the bolt in units compatible with the torque to be calculated.

FAQs - Standard DTIs