Lock nuts typically fall into two categories.
Top lock nut markings.
All metal locknuts prevailing torque cone type iso 7042 7720 class 9 cone din 980v.
Cone flange type iso 7044.
Center lock flange type din 6927.
Such markings differ based on how the fasteners were made.
The above chart should not be considered all inclusive for the fasteners listed the nuts listed are those that are readily available.
Top lock distorted thread locknuts class 8.
Collar type din 934.
This section contains information on the correct usage and identification of bolts flat washers lock wash ers nuts lock nuts fittings and torque data.
Instructions for identification for bolts and studs specification and material codes grade marking required markings astm a 490 type 2 heavy series.
Fasteners commonly have two different markings.
Top lock flange type din 6927.
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.
The nuts bolts and washers used on the airplane are in accordance with air force navy specifications military specifications and national aircraft standards.
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.
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.
Manufacture s identification mark e g x applied to head raised or depressed at option of manufacturer.
Full hex nut type din 934.
Nuts coated cadmium shall have a plus sign marked after the grade symbol.
A 4 9 0 x symbol for identification of grade i e a490 applied to head.
Bolt heads and nuts are often marked with numbers letters dashes slashes dots or an assortment of other marks.
Both markings will be acceptable for a transition period.
All metal lock nuts the most common design is a nut with a crowned top looks like an upside down wheel nut.
Common names for all metal lock nuts are.
2 way reversible lock nuts flex type lock nuts stover lock nuts.
Jam center lock iso.
Medium strength steel top lock distorted thread locknuts grade 5.
Cone asme b18 16 m.
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.
A unique manufacturer identification symbol such as letters or an insignia and information about the fastener strength.
The crowned top is crimped to create a prevailing torque feature that increases the nut s resistance to loosening.
