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Hex Nut with Collar Dimensions (DIN 6331, M6 to M48)

Guide · Updated October 28, 2026

DIN 6331 covers hexagon nuts with collar, height 1.5 d. Wrench size s, nut height m, collar height a and collar diameter d1 agree for every row across the fasteners.eu DIN 6331 table, the Boltsfastener DIN 6331 table and a distributor DIN 6331 PDF sheet; the Elesa+Ganter and Dold Mechatronik catalog sheets match M6 to M36. Not shown: width across corners (the catalogs round it differently from the standard tables, e.g. 11.5 vs 11.05 mm at M6) and M14 (sold by some catalogs but not on the standard sheet). Check the current edition or your supplier for critical work.

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Step by step

  1. Confirm the type: DIN 6331 is a tall hex nut (height about 1.5 x d) with a round collar (shoulder) under the hex. It is the classic fixture and machine-table clamping nut, usually class 10 steel, blackened.
  2. Pick the wrench: s is the wrench size: M6 10 mm, M8 13 mm, M10 16 mm, M12 18 mm, M16 24 mm, M20 30 mm, M24 36 mm. M10 to M12 are smaller than the ISO 4032 hex (17 and 19 mm on some makers), so check before reaching for a wrench.
  3. Check the height: m is the total nut height including the collar: 1.5 x d, so M12 is 18 mm and M16 is 24 mm.
  4. Check the collar: d1 is the collar diameter and a is the collar height. The collar spreads load like a washer: M12 has a 25 mm collar, 4 mm tall.
  5. Check the clamp slot: The collar must bear on solid metal. For a T-slot clamp or strap clamp, the strap hole and slot must be narrower than d1 so the collar does not sink in.
  6. Tighten: Use a calibrated wrench and torque for the stud class. The tall nut carries more thread engagement, which is why it survives repeated clamping and unclamping.

DIN 6331 hex nut with collar dimensions (mm)

Columns: thread size, coarse pitch P, wrench size s, nut height m (including collar), collar height a, collar diameter d1.

Worked example: M12 fixture clamp

An M12 DIN 6331 nut takes an 18 mm wrench, stands 18 mm tall and has a 25 mm collar 4 mm high. On a strap clamp 16 mm thick, the stud must stick out at least 16 + 18 = 34 mm above the strap seat for full engagement; leave a couple of threads past the nut, so about 37 mm. A strap slot of 13 to 14 mm leaves plenty of collar bearing on each side.

DIN 6331 vs ISO 4032 vs ISO 4161

Common problems

FAQ

What is a DIN 6331 nut?

A hex nut with an integral collar and a height of 1.5 times the thread diameter. It is used on fixtures, vises and machine tables where nuts are tightened and loosened often.

Why is DIN 6331 taller than a normal nut?

The 1.5d height gives more engaged threads, so the threads wear less with repeated clamping and the nut can carry high class 10 loads.

Do I need a washer with a DIN 6331 nut?

Usually not. The collar acts as a built-in washer and spreads the load over the clamp strap.

What wrench fits a DIN 6331 M12 nut?

18 mm per the standard sheet. M8 is 13 mm, M10 is 16 mm, M16 is 24 mm. Some catalogs offer M10 with a 17 mm hex on request.

Is there an M14 DIN 6331?

Not on the standard sheet. Some catalogs sell an M14 version, but it is not covered here.

How is it different from a DIN 508 T-slot nut?

DIN 508 is the nut that sits inside the T-slot. DIN 6331 is the collar nut on top of the clamp strap, threaded onto the same stud.

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