Bristol Keys

This multiple spline drive system is recognized by design engineers as the superior method of transmitting torque.  

Reason: nearly 100% of wrenching force is applied at right angles to the load bearing spline surfaces of the

Other drive systems dissipate a significant amount of force into radial thrust,tending to expand the socket rather than tighten the screw.

The substantial and effective wrench engagement inherent in the Bristol design addresses the problems caused by other fastening systems such as cam-out, socket reaming and "rounding" of wrenches.