# Cross dowels / barrel nuts M4–M10 (furniture bolt nuts): barrel diameter and length by thread

> What are the diameter and length of an M6 cross dowel (barrel nut) for a bed or table bolt?

- Category: Hardware › Fasteners
- Kind: Standard part
- Basis: Essentra Components' cross dowel page (four items) and Fastenright's cross dowel table (52 rows, M4 to M10); numbers only
- Page: https://xemstudio.com/objects/cross-dowels-barrel-nuts-m4-m10/ · JSON: https://xemstudio.com/api/geometry?object=cross-dowels-barrel-nuts-m4-m10 · Plain text: https://xemstudio.com/objects/cross-dowels-barrel-nuts-m4-m10/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/)

**Exact dimensions.** True size, with no tolerance added.

## Notes

- Millimetres. A cross dowel (barrel nut, cross-dowel nut) is a cylinder with a threaded hole across its diameter, set in a bored hole in the wood so a bolt in the end of the board threads into it. Essentra lists M6 at Ø10 × 13, 16 and 20 mm (zinc alloy, crossed drive) and M8 at Ø12 × 18 mm (steel, slotted): thread size, outside diameter (barrel diameter), overall length, material and drive; no hole sizes.
- Fastenright's table has four columns: thread diameter, barrel diameter, L1 and L2, all mm. It does not define L1 and L2. Fastenright's L1 values include every Essentra overall length (M6 × Ø10: 13, 16, 20; M8 × Ø12: 18), so L1 reads as the overall length; L2 is usually half of L1 (for example 16 / 8, 20 / 10, 30 / 15) but not always (M6 × 10 × 16 has L2 5, 6 and 8; M6 × 10 × 12.5 has 5; M6 × 10 × 25 has 12.5 and 10), so it is not defined here and may be the cross-hole position from one end. The existing page cross-dowel-m6 carries one retailer's M6 × Ø10 × 30 barrel nut, which Fastenright lists with L2 15 and 10.
- The standard drill-hole sizes for the bore the barrel sits in and the bolt hole are not printed on either page; furniture makers publish those in their drilling jigs, and none was read here. No file: the cross-hole position and thread depth are not defined in the sheets, so no model is drawn.
- Tee nuts for wood: tee-nuts-for-wood-3-4-prong. Flat-pack bolts are usually M6 with a hex or Allen head; see hex-head-screws-metric and socket-head-cap-screws-metric.

## Sizes

| source | thread | barrel diameter (mm) | length / L1 (mm) | L2 (mm, as printed) | note |
|---|---|---|---|---|---|
| Essentra | M6 | 10 | 13 | — | zinc alloy, crossed (Pozidriv-type) |
| Essentra | M6 | 10 | 16 | — | zinc alloy, crossed |
| Essentra | M6 | 10 | 20 | — | zinc alloy, crossed |
| Essentra | M8 | 12 | 18 | — | steel, slotted |
| Fastenright | M4 | 8 | 12 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M4 | 8 | 16 | 8 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M4 | 8 | 20 | 10 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M5 | 8 | 12 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M5 | 8 | 16 | 8 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M5 | 8 | 20 | 10 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 12 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 12.5 | 5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 13 | 5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 14 | 5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 14 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 14 | 7 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 15 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 15 | 7.5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 16 | 5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 16 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 16 | 8 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 17 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 18 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 18 | 9 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 19 | 9.5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 20 | 10 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 22 | 11 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 25 | 12.5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 25 | 10 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 30 | 15 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 30 | 10 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 35 | 17.5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 35 | 10 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 10 | 40 | 20 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 12 | 12 | 5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 12 | 16 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 12 | 16 | 8 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M6 | 16 | 12 | 5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 12 | 6 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 14 | 7 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 16 | 8 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 18 | 9 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 20 | 10 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 20 | 8 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 25 | 12.5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 30 | 15 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 35 | 17.5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 40 | 20 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 45 | 22.5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 50 | 25 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M8 | 12 | 60 | 30 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M10 | 16 | 20 | 10 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M10 | 16 | 25 | 12.5 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M10 | 16 | 30 | 15 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M10 | 16 | 40 | 20 | L1 and L2 as printed (not defined on the page) |
| Fastenright | M10 | 16 | 50 | 25 | L1 and L2 as printed (not defined on the page) |

## Where the files are

- Essentra Components: [Cross dowel barrel nuts: M6 13 / 16 / 20 mm and M8 18 mm, outside diameter 10 and 12 mm, overall length, material, drive](https://www.essentracomponents.com/en-gb/p/cross-dowel-barrel-nuts) — web — Maker catalogue page; numbers only
- Fastenright: [Cross dowel barrel nuts: thread diameter, barrel diameter, L1 and L2 (not defined on the page), M4 to M10](https://www.fastenright.com/general-fixings/cross-dowel-barrel-nut/ff04) — web — Maker catalogue page; numbers only

## Questions

**What size is an M6 cross dowel?**

Barrel diameter 10 mm; lengths 12 to 40 mm in Fastenright's table, 13, 16 and 20 mm at Essentra. M6 Ø12 and Ø16 barrels also exist.

**What is the barrel diameter of an M8 cross dowel?**

12 mm (Essentra and Fastenright), in lengths 12 to 60 mm at Fastenright.

**What is L2 in a cross dowel table?**

Fastenright does not define it; it is often half of L1 but not always, so check the maker's drawing.

## Fits with

- [Cross dowels (barrel nuts) M6 × Ø10 × 30 for flat-pack bed and table bolts](https://xemstudio.com/objects/cross-dowel-m6/)
- [Tee nuts (T-nuts) for wood, 3 and 4 prong, 4-40 to 3/8-16: barrel, flange, prong height, drill size + hole gauge](https://xemstudio.com/objects/tee-nuts-for-wood-3-4-prong/)
- [Hex head screws, M3–M8 (ISO 4017)](https://xemstudio.com/objects/hex-head-screws-metric/)
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/)
- [Rivet nuts (blind threaded inserts), flat head: hole size, grip range, body and flange dimensions, M3–M12 and #6-32 to 3/8-16](https://xemstudio.com/objects/rivet-nuts-flat-head/)