Nord-Lock Locking Washers
Nord-Lock washers are designed to prevent threaded fasteners from loosening. Each Nord-Lock consists of two washers with interlocking faces. The cam angle on the interlocking faces is greater than the thread pitch angle, effectively increasing the torque required to loosen the fastener.
The NLCS-SP Series washers have a relatively large OD, similar to a standard flat washer. They are designed for use under a standard hex bolt head or a nut.
The NLCS Series washers have a small OD that matches the head OD on standard socket-head cap screws ("Allen" screws). This allows their use in a recessed hole that is just large enough to accept the "Allen" head.