Most commonly used locknuts, made of low carbon steel, these locknuts are the least expensive but require a lockwasher and the cutting of a keyway in the shaft.

This series meeting SAE-Society of the Automotive Engineers, ABEC-Annular Bearing Engineers Committee and AFBMA- Anti-Friction Bearing Manufacturers Association specifications offers a positive mechanical lock when combined with a lockwasher and keyway.

An 'A' before the locknut designation indicates this size was previously manufactured with 11 threads per inch whereas now they have either 12 or 8 threads per inch. It is recommended that everyone avoid making shaft threads to this now semi-obsolete 11 pitch series. All new designs could best use the 12 and 8 pitch AN series of threads for the greatest assurance of long term compatibility and future availability.

This N-AN series through size AN-26 meets the many exacting requirements for good operation of tapered roller bearings but series PN in all sizes meets specifications for the safest and best operation of tapered roller bearings.