# Coupling nuts / long hex nuts: DIN 6334 M8–M36 (height 3 d) and inch rod coupling nuts 1/4 to 1 in — across flats, length + M8–M36 envelope models

> What are the dimensions of a DIN 6334 long hex nut, and how long is a 3/8-16 coupling nut?

- Category: Hardware › Fasteners
- Kind: Standard part
- Basis: dinmark's DIN 6334 table (checked at M12 against a Wuerth listing); two inch coupling-nut tables (American Fastener and Alma Bolt) that disagree and are shown side by side; eight DIN 6334 envelope models as files
- Page: https://xemstudio.com/objects/coupling-nuts-din-6334-and-inch/ · JSON: https://xemstudio.com/api/geometry?object=coupling-nuts-din-6334-and-inch · Plain text: https://xemstudio.com/objects/coupling-nuts-din-6334-and-inch/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 15.0 | 13.0 | 24.0 |

**Exact dimensions.** Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part.

## Notes

- DIN 6334 is the hexagon nut with a height of 3 × d (a long nut, used to join two threaded rods or studs, or as a spacer / tensioner). dinmark's table, M8 to M36, gives pitch (coarse), width across flats s and height m (m = 3 d: 24 for M8, 30 for M10, 36 for M12, 48 for M16, 60 for M20, 72 for M24, 90 for M30, 108 for M36). The page prints no width across corners. A Wuerth listing for the M12 nut (WN 6334, steel class 8) prints height 36 mm, width across corners 21.1 mm and a wrench size WS19; that is the only second source read, and it matches dinmark's s 19 and m 36. M6 and the 1.5 d version are not on this page.
- Inch coupling nuts: no standard is cited by either source. American Fastener's sheet (1/4 to 1 in) and Alma Bolt's rod coupling nut table (1/4-20 to 1-8) agree on the hex size for 1/4 (3/8 across flats), 5/16 (1/2) and, for the shorter 3/8 nut, but disagree elsewhere. Length of the 1/4 nut: 3/4 in (American Fastener) against 7/8 in (Alma). 3/8: American Fastener 9/16 across flats × 1-1/8 long; Alma lists 1/2 × 1-1/8 and 9/16 × 1-3/4. 1/2: 3/4 × 1-1/2 against 11/16 × 1-3/4. 5/8: 15/16 × 1-7/8 against 13/16 × 2-1/8. 3/4: 1-1/8 × 2-1/4 against 1 × 2-1/4. 1: 1-1/2 × 3 against 1-3/8 × 2-3/4. Alma also lists a second 5/16 nut (1-1/8 long, against 7/8 and American Fastener's 15/16). Both sets are shown; no inch file is drawn because the dimensions are not settled. Alma's source text lists the last size as '1/8', read as 1-8.
- Files are Xem-drawn envelopes of DIN 6334: a hexagon at the published width across flats and height 3 d with a plain bore at the thread major diameter (the real thread is smaller); no chamfers on the corners or faces. Hexagon corners are across-flats / cos 30°.
- McMaster-Carr sells coupling nuts (inch and reducing) with per-part STEP; its Grade 2 steel coupling-nut page is linked, not copied. Standard hex nuts: hex-nuts-metric, hex-nuts-inch.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| bore (thread as plain cylinder) | thread major diameter M8 to M36: Ø8 … Ø36 mm | threaded rod or stud of the same thread (plain cylinder at the major Ø) | designed | din-6334-* |
| hex body | s across flats × height 3 d: M8 13 × 24, M10 17 × 30, M12 19 × 36, M16 24 × 48, M20 30 × 60, M24 36 × 72, M30 46 × 90, M36 55 × 108 mm | hex pocket capturing the nut: width = s, depth = height | slide | din-6334-* |

## Sizes

| standard / source | size | pitch | width across flats | width across corners | length / height | note |
|---|---|---|---|---|---|---|
| DIN 6334 (dinmark) | M8 | 1.25 mm | 13 mm | — | 24 mm (= 3 d) | — |
| DIN 6334 (dinmark) | M10 | 1.5 mm | 17 mm | — | 30 mm (= 3 d) | — |
| DIN 6334 (dinmark) | M12 | 1.75 mm | 19 mm | — | 36 mm (= 3 d) | — |
| DIN 6334 (dinmark) | M16 | 2 mm | 24 mm | — | 48 mm (= 3 d) | — |
| DIN 6334 (dinmark) | M20 | 2.5 mm | 30 mm | — | 60 mm (= 3 d) | — |
| DIN 6334 (dinmark) | M24 | 3 mm | 36 mm | — | 72 mm (= 3 d) | — |
| DIN 6334 (dinmark) | M30 | 3.5 mm | 46 mm | — | 90 mm (= 3 d) | — |
| DIN 6334 (dinmark) | M36 | 4 mm | 55 mm | — | 108 mm (= 3 d) | — |
| inch, American Fastener (no standard cited) | 1/4 | — | 3/8 in (0.375 / 0.365) | 0.433 / 0.416 in | 3/4 in (0.76 / 0.74) | — |
| inch, American Fastener (no standard cited) | 5/16 | — | 1/2 in (0.500 / 0.489) | 0.577 / 0.557 in | 15/16 in (0.95 / 0.93) | — |
| inch, American Fastener (no standard cited) | 3/8 | — | 9/16 in (0.562 / 0.551) | 0.650 / 0.628 in | 1-1/8 in (1.13 / 1.11) | — |
| inch, American Fastener (no standard cited) | 1/2 | — | 3/4 in (0.750 / 0.736) | 0.866 / 0.839 in | 1-1/2 in (1.51 / 1.49) | — |
| inch, American Fastener (no standard cited) | 5/8 | — | 15/16 in (0.938 / 0.922) | 1.083 / 1.051 in | 1-7/8 in (1.89 / 1.86) | — |
| inch, American Fastener (no standard cited) | 3/4 | — | 1-1/8 in (1.125 / 1.088) | 1.299 / 1.240 in | 2-1/4 in (2.27 / 2.22) | — |
| inch, American Fastener (no standard cited) | 1 | — | 1-1/2 in (1.500 / 1.450) | 1.732 / 1.653 in | 3 in (3.03 / 2.97) | — |
| inch, Alma Bolt (no standard cited) | 1/4-20 | coarse as named | 3/8 in (0.375 / 0.365) | 0.433 / 0.416 in | 7/8 in (0.89 / 0.86) | differs from American Fastener at several sizes |
| inch, Alma Bolt (no standard cited) | 5/16-18 | coarse as named | 1/2 in (0.500 / 0.489) | 0.577 / 0.557 in | 7/8 in (0.89 / 0.86) | differs from American Fastener at several sizes |
| inch, Alma Bolt (no standard cited) | 5/16-18 | coarse as named | 1/2 in (0.500 / 0.489) | 0.577 / 0.557 in | 1-1/8 in (1.13 / 1.11) | differs from American Fastener at several sizes |
| inch, Alma Bolt (no standard cited) | 3/8-16 | coarse as named | 1/2 in (0.500 / 0.489) | 0.577 / 0.557 in | 1-1/8 in (1.13 / 1.11) | differs from American Fastener at several sizes |
| inch, Alma Bolt (no standard cited) | 3/8-16 | coarse as named | 9/16 in (0.562 / 0.551) | 0.650 / 0.628 in | 1-3/4 in (1.76 / 1.73) | differs from American Fastener at several sizes |
| inch, Alma Bolt (no standard cited) | 1/2-13 | coarse as named | 11/16 in (0.688 / 0.663) | 0.794 / 0.756 in | 1-3/4 in (1.76 / 1.73) | differs from American Fastener at several sizes |
| inch, Alma Bolt (no standard cited) | 5/8-11 | coarse as named | 13/16 in (0.813 / 0.782) | 0.939 / 0.891 in | 2-1/8 in (2.14 / 2.10) | differs from American Fastener at several sizes |
| inch, Alma Bolt (no standard cited) | 3/4-10 | coarse as named | 1 in (1.000 / 0.963) | 1.155 / 1.097 in | 2-1/4 in (2.27 / 2.22) | differs from American Fastener at several sizes |
| inch, Alma Bolt (no standard cited) | 1-8 | coarse as named | 1-3/8 in (1.375 / 1.325) | 1.588 / 1.511 in | 2-3/4 in (2.78 / 2.72) | differs from American Fastener at several sizes |

## Where the files are

- dinmark: [DIN 6334 high hexagon nut: thread, pitch, s (across flats), m (height) M8 to M36](https://dinmark.com.ua/en/shop/hayky/hayky-shestyhranni/din-6334-hayka-vysoka-shestyhranna/din-6334-10-hayka-vysoka-shestyhranna) — web — Distributor page; numbers only
- Wuerth: [Hexagonal nut 3 x d high WN 6334, M12: height 36, width across corners 21.1, wrench size WS19](https://eshop.wuerth-ag.ch/Hexagonal-nut-3xd-high-WN-6334-steel-8-plain-NUT-HEX-WN6334-8-WS19-M12/5140112.sku/en/US/CHF) — web — Maker shop page; numbers only
- American Fastener: [Hex coupling nuts: nominal size, width across flats and corners, length (basic / max / min), 1/4 to 1 (no standard cited)](https://www.americanfastener.com/wp-content/uploads/2020/06/NUTS-HEX-COUPLING-AMERICAN-FASTENER.pdf) — web — Maker data sheet; numbers only
- Alma Bolt: [Rod coupling nuts (hex coupling nuts): size, major diameter, across flats / corners, length (basic / max / min), 1/4-20 to 1-8 (no standard cited)](https://almabolt.com/pages/catalog/nuts/coupling.htm) — web — Distributor catalog; numbers only
- McMaster-Carr: [Grade 2 steel coupling nuts (free STEP/IGES per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/grade-2-steel-coupling-nuts/) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)

## Free STEP/STL (8 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/index.json

- din-6334-m8-long-hex-nut-envelope: [STEP](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m8-long-hex-nut-envelope.step) · [STL](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m8-long-hex-nut-envelope.stl) — DIN 6334 M8 long hexagon nut envelope: hex 13 mm across flats × 24 mm high (3 × d), bore Ø8 (thread major diameter as a plain cylinder); no chamfers, no thread
- din-6334-m10-long-hex-nut-envelope: [STEP](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m10-long-hex-nut-envelope.step) · [STL](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m10-long-hex-nut-envelope.stl) — DIN 6334 M10 long hexagon nut envelope: hex 17 mm across flats × 30 mm high (3 × d), bore Ø10 (thread major diameter as a plain cylinder); no chamfers, no thread
- din-6334-m12-long-hex-nut-envelope: [STEP](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m12-long-hex-nut-envelope.step) · [STL](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m12-long-hex-nut-envelope.stl) — DIN 6334 M12 long hexagon nut envelope: hex 19 mm across flats × 36 mm high (3 × d), bore Ø12 (thread major diameter as a plain cylinder); no chamfers, no thread
- din-6334-m16-long-hex-nut-envelope: [STEP](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m16-long-hex-nut-envelope.step) · [STL](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m16-long-hex-nut-envelope.stl) — DIN 6334 M16 long hexagon nut envelope: hex 24 mm across flats × 48 mm high (3 × d), bore Ø16 (thread major diameter as a plain cylinder); no chamfers, no thread
- din-6334-m20-long-hex-nut-envelope: [STEP](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m20-long-hex-nut-envelope.step) · [STL](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m20-long-hex-nut-envelope.stl) — DIN 6334 M20 long hexagon nut envelope: hex 30 mm across flats × 60 mm high (3 × d), bore Ø20 (thread major diameter as a plain cylinder); no chamfers, no thread
- din-6334-m24-long-hex-nut-envelope: [STEP](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m24-long-hex-nut-envelope.step) · [STL](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m24-long-hex-nut-envelope.stl) — DIN 6334 M24 long hexagon nut envelope: hex 36 mm across flats × 72 mm high (3 × d), bore Ø24 (thread major diameter as a plain cylinder); no chamfers, no thread
- din-6334-m30-long-hex-nut-envelope: [STEP](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m30-long-hex-nut-envelope.step) · [STL](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m30-long-hex-nut-envelope.stl) — DIN 6334 M30 long hexagon nut envelope: hex 46 mm across flats × 90 mm high (3 × d), bore Ø30 (thread major diameter as a plain cylinder); no chamfers, no thread
- din-6334-m36-long-hex-nut-envelope: [STEP](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m36-long-hex-nut-envelope.step) · [STL](https://xemstudio.com/files/hardware/coupling-nuts-din-6334-and-inch/din-6334-m36-long-hex-nut-envelope.stl) — DIN 6334 M36 long hexagon nut envelope: hex 55 mm across flats × 108 mm high (3 × d), bore Ø36 (thread major diameter as a plain cylinder); no chamfers, no thread

## Questions

**How long is an M10 DIN 6334 nut?**

30 mm (3 × d) and 17 mm across flats, per dinmark's DIN 6334 table.

**How long is a 1/2-13 coupling nut?**

The two inch tables read disagree: 1-1/2 in long and 3/4 in across flats (American Fastener) or 1-3/4 in long and 11/16 in across flats (Alma Bolt). Check the nut you buy.

**What wrench fits an M12 DIN 6334 nut?**

19 mm across flats (dinmark and Wuerth WS19); the nut is 36 mm long.

## Fits with

- [Hex nuts, M2–M8 (ISO 4032)](https://xemstudio.com/objects/hex-nuts-metric/)
- [Hex nuts, M10 to M24 (ISO 4032 / DIN 934)](https://xemstudio.com/objects/hex-nuts-metric-m10-m24/)
- [Hex nuts, inch: #4-40 to 3/4-10 (ASME B18.2.2)](https://xemstudio.com/objects/hex-nuts-inch/)
- [Slotted and castle nuts, DIN 935-1, M4–M36: across flats, height, slot width, collar, cotter pin size + envelope models](https://xemstudio.com/objects/slotted-castle-nuts-din-935/)
- [Threaded rod, metric M3 to M12 (DIN 976), 100 to 1000 mm](https://xemstudio.com/objects/threaded-rod-metric-din-976/)
- [Threaded rod, inch: #4 to 4 in, UNC and UNF threads per inch, major diameter in inches and mm, standard lengths](https://xemstudio.com/objects/threaded-rod-inch-unc-unf-sizes/)
- [Threaded rod, metric: M4 × 194.2](https://xemstudio.com/objects/threaded-rods-metric/)
- [Lifting eye nuts, DIN 582, M6–M100x6: ring, collar, height and thread](https://xemstudio.com/objects/eye-nuts-din-582/)