The magnet body is attached to the rear of the motor or bulkhead, and the hub is attached to the shaft with two set screws. When the coil is energized, the electromagnetic field attracts the armature plate and compresses the springs. This allows the friction plate to rotate freely with the hub and shaft.
When power is turned off, the electromagnetic field dissipates,allowing the springs to push the armature plate into contact with the friction disk. This squeezes the friction disk between the pressure plate and the armature plate, thus transmitting torque, and stopping/holding the friction disc, hub, and shaft.