The E48 Safety key interlock switch is designed for use with moveable guards, covers or doors which must be closed for operational safety. The switch is mounted to a rigid portion of the machine. The operation key (typically affixed to a moveable guard, cover or door) directly pulls NC contacts apart which interrupts the control circuit and stops machine operation. When the guard, cover or door is opened, the key is removed from the switch, thereby directly opening the NC contacts. The head mechanism is designed to be difficult to defeat with common tools.