Direct Tension Control-Alternative Design Bolts
The alternative design bolts incorporate a design feature, which is intended to indirectly indicate tension. The most common type of this bolt is the “twist-off bolt” (tension control bolts). An assembly tool holds
this bolt from the nut end. An inner spindle on the tool grips a spline section connected to the main portion
of the bolt. An outer spindle on the tool turns the nut and tightens the fastener. When the design torque has been reached, the reaction forces on the spline snap it off.
