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Hex Domed Cap Nut Dimensions (DIN 1587, M4 to M24)

Guide · Updated October 28, 2026

DIN 1587 covers high-form hex domed cap nuts (acorn nuts) M4 to M24. Pitch P, wrench size s, e min (grade A), total height h, dome diameter dk max and thread depth t agree across the HBS Solutions DIN 1587 data sheet, the fasteners.eu DIN 1587 table and the DigiPich DIN 1587 table. Not shown: nut part height m, because the sources disagree at M10 (8 vs 8.8 mm max), plus grade B tolerances and weights. Check the current edition or your supplier for critical work.

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Step by step

  1. Confirm the size: DIN 1587 covers high-form hex domed cap (acorn) nuts M4 to M24, coarse pitch in series 1, with fine-pitch options from M8 up.
  2. Pick the wrench: s is the wrench size across flats: M6 10 mm, M8 13 mm, M10 16 mm, M12 18 mm.
  3. Check the total height: h is the overall height to the top of the dome: M8 15 mm, M10 18 mm. Allow this much clearance above the part.
  4. Check the thread depth: t is how deep the blind thread goes: M8 10.65 to 11.35 mm. The bolt must stick out less than t or it bottoms in the dome.
  5. Size the bolt: Bolt length = grip + a projection shorter than t min. If the bolt is too long the nut seizes against the dome before it clamps.
  6. Check dome clearance: dk max is the dome diameter, a little under s, so it fits any socket that fits the hex.

DIN 1587 domed cap nut dimensions (mm)

Columns: thread size, coarse pitch P, wrench size s, width across corners e min (grade A), total height h, dome diameter dk max, thread depth t min–max. Sizes in brackets are non-preferred.

Worked example: M8 acorn nut on a guard

An M8 DIN 1587 nut takes a 13 mm wrench, stands 15 mm tall and has 10.65 to 11.35 mm of thread depth. Clamping a 6 mm guard plus a 2 mm washer is 8 mm of grip. An M8 x 16 bolt projects 8 mm past the washer, safely under the 10.65 mm minimum depth. An M8 x 20 would project 12 mm and bottom out in the dome before the joint is tight.

DIN 1587 vs a standard hex nut

DIN 1587 wrench sizes match ISO 4032 hex nuts: M6 10, M8 13, M10 16, M12 18, M16 24, M20 30, M24 36 mm. Older DIN 934 M10 and M12 nuts used 17 and 19 mm, so check mixed stock before grabbing a socket.

Common problems

FAQ

What is a DIN 1587 nut?

A hex domed cap nut, also called an acorn nut, high form. The closed dome covers the bolt end for looks and to protect hands and threads.

How long should the bolt be for an acorn nut?

The bolt end must project less than the thread depth t min, for example under 10.65 mm on M8 and under 12.65 mm on M10, or the bolt bottoms out in the dome.

What wrench fits a DIN 1587 M8 acorn nut?

13 mm, the same as a standard M8 hex nut. M10 is 16 mm and M12 is 18 mm.

How is DIN 1587 different from DIN 917?

DIN 917 is a low-form cap nut with a flat or shallow closed top. DIN 1587 is the high form with a full dome, so it is taller and has deeper thread.

Are sizes in brackets standard?

M14, M18 and M22 are non-preferred sizes. Stock is easier for M4 to M12, M16, M20 and M24.

Can I torque an acorn nut like a normal nut?

Only if the bolt does not bottom out. Many are two-piece pressed parts in stainless or plated steel, so check the supplier rating.

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General shop information only — follow your drawing, tool maker's data and your quality system.