Top Lock Nut Markings

Fasteners commonly have two different markings.

Top lock nut markings.

2 way reversible lock nuts flex type lock nuts stover lock nuts. Collar type din 934. 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. Instructions for identification for bolts and studs specification and material codes grade marking required markings astm a 490 type 2 heavy series.

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. Jam center lock iso. Common names for all metal lock nuts are. Such markings differ based on how the fasteners were made.

The nuts bolts and washers used on the airplane are in accordance with air force navy specifications military specifications and national aircraft standards. Medium strength steel top lock distorted thread locknuts grade 5. 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. Gr8 hex nut type.

These graded identification markings show the latest revision. Cone flange type iso 7044. Manufacture s identification mark e g x applied to head raised or depressed at option of manufacturer. All metal lock nuts the most common design is a nut with a crowned top looks like an upside down wheel nut.

The crowned top is crimped to create a prevailing torque feature that increases the nut s resistance to loosening. Bolt heads and nuts are often marked with numbers letters dashes slashes dots or an assortment of other marks. All metal locknuts prevailing torque cone type iso 7042 7720 class 9 cone din 980v. Cone asme b18 16 m.

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. Full hex nut type din 934. A 4 9 0 x symbol for identification of grade i e a490 applied to head. Nuts coated cadmium shall have a plus sign marked after the grade symbol.

Both markings will be acceptable for a transition period. Top lock distorted thread locknuts class 8. Lock nuts typically fall into two categories. This section contains information on the correct usage and identification of bolts flat washers lock wash ers nuts lock nuts fittings and torque data.

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