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.

Center lock flange type din 6927. Full hex nut type din 934. Instructions for identification for bolts and studs specification and material codes grade marking required markings astm a 490 type 2 heavy series. Medium strength steel top lock distorted thread locknuts grade 5.

Lock nuts typically fall into two categories. Fasteners commonly have two different markings. The nuts bolts and washers used on the airplane are in accordance with air force navy specifications military specifications and national aircraft standards. 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.

Bolt heads and nuts are often marked with numbers letters dashes slashes dots or an assortment of other marks. This section contains information on the correct usage and identification of bolts flat washers lock wash ers nuts lock nuts fittings and torque data. Such markings differ based on how the fasteners were made. Nuts coated cadmium shall have a plus sign marked after the grade symbol.

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. 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. Both markings will be acceptable for a transition period.

Top lock distorted thread locknuts class 8. Collar type din 934. Cone flange type iso 7044. These graded identification markings show the latest revision.

A 4 9 0 x symbol for identification of grade i e a490 applied to head. Common names for all metal lock nuts are. Top lock flange type din 6927. Jam center lock iso.

All metal lock nuts the most common design is a nut with a crowned top looks like an upside down wheel nut. Gr8 hex nut type. A unique manufacturer identification symbol such as letters or an insignia and information about the fastener strength. 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. 2 way reversible lock nuts flex type lock nuts stover lock nuts.