SJS® Super Joint System is a mechanical clutch system that helps prevent motor and gear damage in grinders if the wheel is forced to a stop. The drive shaft from the armature to the drive gear is spring-loaded during normal grinding load. If binding occurs or the wheel is forced to stop, the spring is compressed allowing the drive shaft to slip. The gear tension is minimized while the armature continues to rotate, which helps prevent motor burn-out. SJS® is a mechanical clutch system, not elecronic, so the grinder does not require a re-start if the wheel binds. [Learn More]