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Low Hex Cap Nut Dimensions (DIN 917, M4 to M20)

Guide · Updated October 28, 2026

DIN 917 covers low form hexagon cap nuts. Pitch P, wrench size s, height h, blind hole depth t, crown radius r and wall w agree across the DigiPich DIN 917 table, the fasteners.eu DIN 917 table and the Dueemme Sidol DIN 917 sheet; fasten.it agrees on t and r. Not shown: the 16 / 18 / 21 mm wrench variants for M10 / M12 / M14 (fasten.it lists these as the main width, the other sources as alternatives), fine-pitch rows and M22 and up (only two sources go that far). fasten.it lists M20 h as 24.48 mm, which is the h min in the other sources; 25 mm nominal is shown. Check the current edition or your supplier for critical work.

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Step by step

  1. Confirm the size: DIN 917 is the low form hex cap nut (cup nut): a hex nut with a closed, flat-topped crown. It is much shorter than the domed DIN 1587 acorn nut. This chart shows M4 to M20 coarse pitch.
  2. Pick the wrench: s is the wrench size: M6 10 mm, M8 13 mm, M10 17 mm, M12 19 mm, M16 24 mm, M20 30 mm. Some ISO-width versions use 16 / 18 / 21 mm for M10 / M12 / M14, so check the part.
  3. Check the height: h is the overall height: M8 12 mm, M10 14 mm, M12 16 mm, M16 20 mm.
  4. Check the blind hole: t is the depth of the closed hole from the bearing face: M8 9.21 to 9.79 mm, M12 13.15 to 13.85 mm. The bolt must stop short of t min.
  5. Size the bolt: Bolt projection past the clamped parts must be less than t min, and long enough to fill the thread. If the bolt bottoms out, the nut will feel tight but give no clamp load.
  6. Tighten: Torque as a regular nut of the same class, but watch that the bolt end is not hitting the crown.

DIN 917 low cap nut dimensions (mm)

Columns: thread size, coarse pitch P, wrench size s, width across corners e min, overall height h, blind hole depth t min–max, crown radius r approx, wall thickness w min. Sizes in brackets are non-preferred.

Worked example: M10 low cap nut

An M10 DIN 917 nut takes a 17 mm wrench and stands 14 mm tall. The blind hole is 10.65 to 11.35 mm deep, so the bolt may stick out no more than about 10 mm past the bearing face. Clamping a 20 mm stack plus a 2 mm washer, an M10 x 30 bolt leaves 8 mm of projection and fits. An M10 x 35 leaves 13 mm and will bottom out.

DIN 917 vs DIN 1587 at a glance

Common problems

FAQ

What is a DIN 917 nut?

A low form hex cap nut, also called a cup nut or low acorn nut. The closed top covers the bolt end and thread, but it is shorter than the domed DIN 1587 cap nut.

How is DIN 917 different from DIN 1587?

DIN 1587 is a tall domed acorn nut; DIN 917 is a low, flatter cap. For M10 DIN 917 is 14 mm tall versus 18 mm for DIN 1587, and the blind hole is shallower, so bolt length matters more.

What wrench fits a DIN 917 M10 cap nut?

17 mm. M8 is 13 mm, M12 is 19 mm and M16 is 24 mm.

How long can the bolt stick out?

Less than t min: M6 6.71 mm, M8 9.21 mm, M10 10.65 mm, M12 13.15 mm, M16 16.65 mm. Leave a little margin for washers and tolerance.

Is a cap nut watertight?

Not by itself. The closed end keeps dirt off the thread, but the thread and bearing face can still leak. Add a seal if you need one.

Are M14 and M18 standard?

They are non-preferred sizes (in brackets) and harder to buy.

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