J.W. Winco, Inc. has released GN 3663 Metric Size, Aluminum Torque Limiting Knurled Knobs with Steel Hub.
These knurled knobs are used when manually applied torque is to be limited. When turned clockwise, the torque mechanical system of the knurled knob triggers an "over-engagement" as soon as the specified torque is reached. When tightening, this insures that maximum permissible torque is not exceeded. When turned counter-clockwise, loosening the knob mechanism, the mechanical system locks so that the torque is not limited. Torque necessary for release will always be transmitted properly. After removal of cover and loosening of the countersunk screw, the tapped or threaded stud insert can be dismantled. In addition, versions with inch size tapped holes or threaded studs are available upon request.
The body of these RoHS compliant knobs is aluminum, with a black anodized finish, while the torque mechanism is steel with a blackened finish and the cover cap is plastic with a light gray matte finish.