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DIN 985

Hexagon lock nut,nylon insert

Superseded by ISO 10511 (2012) · Still sold as DIN 985 · Sizes M3–M48
DIN 985 nut cut in half, showing the thread, the nylon insert and the height hDIN 985 nut cut in half, showing the thread, the nylon insert and the height h
Side view, in section
DIN 985 nut seen from its face, with the width across flats (s) and the width across corners eDIN 985 nut seen from its face, with the width across flats (s) and the width across corners e
Face view
SizeP (mm, coarse)s (mm, nom.)e (mm, min)h (mm, max)
M3
0.505.506.013.90
M4
0.707.007.665.00
M5
0.808.008.795.00
M6
1.0010.0011.056.00
M8
1.2513.0014.386.76
M10
1.5016.0017.778.56
M12
1.7518.0020.0310.23
M16
2.0024.0026.7512.42
M20
2.5030.0032.9514.90
M24
3.0036.0039.5517.80

Values per ISO 10511:2012. The values follow this edition; the current one is ISO 10511:2025.Differs from DIN 985

Verified data

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Calculators that use this standard: Bolted joint configurator

About DIN 985

What it is

A hexagon nut with a nylon ring in its top, which the screw thread cuts into: the friction keeps the nut from working loose (a prevailing torque nut). An M10 to DIN 985 takes a 17 mm spanner and is 10 mm high, insert included.

Where it is used

On joints that vibrate or move (machines, vehicles, pivots and hinges), and wherever a nut must stay at a set position without being tightened hard, from M3 to M48.

DIN or ISO

ISO 10511 replaced DIN 985. The ISO nut is lower in most sizes: an M8 is at most 6.76 mm high against 8, an M10 8.56 against 10. M10, M12 and M14 have the ISO 4032 width across flats (16, 18 and 21 mm). ISO 10511 covers M3 to M36 without M18, M22, M27 or M33.

Typical mistakes

  • Choosing a screw that stops inside the insert. The thread must pass right through the nut, with at least two pitches sticking out (ISO 4753).
  • Reusing it again and again. The insert wears at each assembly and holds less.
  • Using it where it gets hot. The nylon insert has a temperature limit; above it, an all-metal lock nut is needed.
  • Bringing a 17 mm spanner to an ISO 10511 M10. It needs 16 mm, as do the ISO hex nuts.
  • Counting on the DIN height with ISO stock: an ISO M10 is at most 8.56 mm high, not 10, and grips fewer threads.

References