Whoops! That’s a fail, and now you have a broken bolt. If you have been turning wrenches for a few years, you have probably developed a sense for what 20-50 ft-lbs of torque feels like. It only ...

From the table, torque coefficients for a 0.250-in.-diameter screw are Cmax = 0.195915 at maximum friction µmax = 0.15; and Cmin = 0.138035 at minimum friction µmin = 0.10.

These values break out to 10.9%, 36.3%, and 52.8%, respectively, of the total torque, confirming the commonly heard assertion that only 10 to 15% of the input torque goes toward stretching the bolt.