Top Lock Nut Markings

The above chart should not be considered all inclusive for the fasteners listed the nuts listed are those that are readily available.

Top lock nut markings. Full hex nut type din 934. Fasteners commonly have two different markings. This section contains information on the correct usage and identification of bolts flat washers lock wash ers nuts lock nuts fittings and torque data. Both markings will be acceptable for a transition period.

The nuts bolts and washers used on the airplane are in accordance with air force navy specifications military specifications and national aircraft standards. Screws are marked on the top of their heads the exceptions being small under about 1 4 slotted and recessed head fasteners where there is insufficient room for head markings. The crowned top is crimped to create a prevailing torque feature that increases the nut s resistance to loosening. All metal prevailing torque type lock nuts achieve their prevailing torque by altering the shape of the nut in some way most commonly by distorting the threads of the nut which then bites into the mating part when tightened.

Cone asme b18 16 m. These metric locknuts have an irregularly shaped thread at the top of the nut that grips the bolt for a stronger hold than nylon insert locknuts. All metal locknuts prevailing torque cone type iso 7042 7720 class 9 cone din 980v. Such markings differ based on how the fasteners were made.

These graded identification markings show the latest revision. All metal lock nuts the most common design is a nut with a crowned top looks like an upside down wheel nut. 2 way reversible lock nuts flex type lock nuts stover lock nuts. These metric locknuts have an irregularly shaped thread at the top of the nut that grips the bolt for a stronger hold than nylon insert locknuts.

Nuts coated cadmium shall have a plus sign marked after the grade symbol. A head with no markings is grade 2 one with 3 lines spaced 120 degrees is grade 5 and 6 lines spaced at 60 degree intervals is grade 8. A unique manufacturer identification symbol such as letters or an insignia and information about the fastener strength. Jam center lock iso.

Common names for all metal lock nuts are. Cone flange type iso 7044. Medium strength steel top lock distorted thread locknuts grade 5. Top lock distorted thread locknuts class 8.

Lock nuts typically fall into two categories. Instructions for identification for bolts and studs specification and material codes grade marking required markings astm a 490 type 2 heavy series. Gr8 hex nut type. A 4 9 0 x symbol for identification of grade i e a490 applied to head.

Manufacture s identification mark e g x applied to head raised or depressed at option of manufacturer. Center lock flange type din 6927.