DIN 985Nylon insert lock nutExternal hexagon

DIN 985 M18 Nylon insert lock nut

DIN 985 M18 is a nylon insert lock nut, on a M18 × 1.5 mm metric thread. A full hex nut with a nylon collar that grips the thread and resists vibration loosening. Note that the nylon insert has a temperature limit — above roughly 120 °C it loses its locking effect.

DIN 985 M18 — Nylon insert lock nutNominal dimensions in mm · Not to scale

Diameter18 mm

Pitch1.5 mm

Socket size s27 mm

Thickness h23 mm

Height m21 mm

DriveExternal hexagon

Dimensions

Standard: DIN 985
Type: Nylon insert lock nut
Size: M18
Thread: M18 × 1.5
Socket size s: 27 mm
Height m: 21 mm
Total height h: 23 mm
Drive: External hexagon

Nominal values in millimetres as published in DIN 985. Estimated weight 36.105 g per piece in steel (36.335 g in stainless), calculated from the nominal geometry — real parts vary with tolerance and head chamfers.

Thread data

Full M18 thread page

DesignationM18 × 1.5 fine

Pitch1.5 mm

Nominal Ø18 mm

Pitch Ø17.03 mm

Minor Ø ext16.16 mm

Tap drillØ 16.5 mm

Other lengthsDIN 985 M18

All M18 specifications

M18

Interchangeability

DIN 985 is catalogued with ISO 10511 as its equivalent designation. Dimensions are compared field by field rather than assumed identical.

Equivalent standardISO 10511Prevailing Torque Hexagon Nut with Non-Metallic Insert ComparisonDIN 985 vs ISO 10511Field-by-field differences and a substitution verdict

Choosing and fitting this size

DIN 985 M18 is a M18 nut, on a 1.5 mm coarse pitch. Mating threads should be a matching class nut in the same property class.

Common stock grades are 8.8, 10.9 and 12.9 in steel, plus A2-70 and A4-80 in stainless. Class 10.9 and 12.9 carry roughly 1.25 and 1.5 times the proof load of 8.8, but they also need a properly rated mating nut — a class 8 nut under a 12.9 bolt simply moves the failure into the thread. Zinc-plated 10.9 and above should be baked to avoid hydrogen embrittlement.

For a tapped hole, M18 × 1.5 mm takes a 16.5 mm tap drill, and the external thread's minor diameter is 16.16 mm — that is the section carrying the load, not the nominal M18 figure. Thread engagement of at least one times the nominal diameter is what lets the bolt fail before the thread strips.