# Hex head screws, M3–M8 (ISO 4017)

> What size hex pocket holds an M5 hex head bolt so it can't turn?

- Category: Hardware › Fasteners
- Kind: Hardware
- Basis: ISO 4017 (fully threaded hex head screws): width across flats s and head height k
- Page: https://xemstudio.com/objects/hex-head-screws-metric/ · JSON: https://xemstudio.com/api/geometry?object=hex-head-screws-metric · Plain text: https://xemstudio.com/objects/hex-head-screws-metric/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

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

## Notes

- Hex head: s across flats, k high, corners s × 1.155. A pocket that keeps the head from turning is drawn at s × k exactly (see Mating features), so a nut can be run down from the other side with one tool.
- Used in the two-bolt tri-clamp clamps: M5 × 30 in the 1½–4 in clamp halves, M8 in the 10 and 12 in clamps; each clamp half has the head pocket on one lug and a plain hole on the other.

## 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 |
|---|---|---|---|---|
| hex head | s × k (M5 8 × 3.5, M8 13 × 5.3; ISO 4017) | hex pocket in a clamp lug | socket | hexbolt-* |
| shank | thread major (M5 Ø5) | clearance hole (ISO 273) and nut | designed | hexbolt-* |

## Sizes

| thread | width_af_mm | corner_mm | head_height_mm | lengths_mm |
|---|---|---|---|---|
| M3 | 5.5 | 6.4 | 2.0 | 10, 16, 20 |
| M4 | 7.0 | 8.1 | 2.8 | 12, 16, 20, 25 |
| M5 | 8.0 | 9.2 | 3.5 | 16, 20, 25, 30, 40 |
| M6 | 10.0 | 11.5 | 4.0 | 20, 25, 30, 40 |
| M8 | 13.0 | 15.0 | 5.3 | 20, 25, 30, 40, 50 |

## Where the files are

- McMaster-Carr: [Hex head screws (free STEP/IGES/STL per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/hex-head-screws/) — STEP, IGES, STL, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)
- Wikipedia: [Screw](https://en.wikipedia.org/wiki/Screw) — web — CC BY-SA 4.0 (text)

## Free STEP/STL (21 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/hex-head-screws-metric/index.json

- hexbolt-m3x10: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m3x10.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m3x10.stl) — ISO 4017 M3 × 10 hex head, 5.5 AF × 2 head, thread as plain cylinder
- hexbolt-m3x16: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m3x16.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m3x16.stl) — ISO 4017 M3 × 16 hex head, 5.5 AF × 2 head, thread as plain cylinder
- hexbolt-m3x20: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m3x20.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m3x20.stl) — ISO 4017 M3 × 20 hex head, 5.5 AF × 2 head, thread as plain cylinder
- hexbolt-m4x12: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m4x12.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m4x12.stl) — ISO 4017 M4 × 12 hex head, 7 AF × 2.8 head, thread as plain cylinder
- hexbolt-m4x16: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m4x16.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m4x16.stl) — ISO 4017 M4 × 16 hex head, 7 AF × 2.8 head, thread as plain cylinder
- hexbolt-m4x20: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m4x20.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m4x20.stl) — ISO 4017 M4 × 20 hex head, 7 AF × 2.8 head, thread as plain cylinder
- hexbolt-m4x25: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m4x25.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m4x25.stl) — ISO 4017 M4 × 25 hex head, 7 AF × 2.8 head, thread as plain cylinder
- hexbolt-m5x16: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x16.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x16.stl) — ISO 4017 M5 × 16 hex head, 8 AF × 3.5 head, thread as plain cylinder
- hexbolt-m5x20: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x20.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x20.stl) — ISO 4017 M5 × 20 hex head, 8 AF × 3.5 head, thread as plain cylinder
- hexbolt-m5x25: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x25.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x25.stl) — ISO 4017 M5 × 25 hex head, 8 AF × 3.5 head, thread as plain cylinder
- hexbolt-m5x30: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x30.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x30.stl) — ISO 4017 M5 × 30 hex head, 8 AF × 3.5 head, thread as plain cylinder
- hexbolt-m5x40: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x40.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m5x40.stl) — ISO 4017 M5 × 40 hex head, 8 AF × 3.5 head, thread as plain cylinder
- hexbolt-m6x20: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m6x20.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m6x20.stl) — ISO 4017 M6 × 20 hex head, 10 AF × 4 head, thread as plain cylinder
- hexbolt-m6x25: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m6x25.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m6x25.stl) — ISO 4017 M6 × 25 hex head, 10 AF × 4 head, thread as plain cylinder
- hexbolt-m6x30: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m6x30.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m6x30.stl) — ISO 4017 M6 × 30 hex head, 10 AF × 4 head, thread as plain cylinder
- hexbolt-m6x40: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m6x40.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m6x40.stl) — ISO 4017 M6 × 40 hex head, 10 AF × 4 head, thread as plain cylinder
- hexbolt-m8x20: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x20.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x20.stl) — ISO 4017 M8 × 20 hex head, 13 AF × 5.3 head, thread as plain cylinder
- hexbolt-m8x25: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x25.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x25.stl) — ISO 4017 M8 × 25 hex head, 13 AF × 5.3 head, thread as plain cylinder
- hexbolt-m8x30: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x30.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x30.stl) — ISO 4017 M8 × 30 hex head, 13 AF × 5.3 head, thread as plain cylinder
- hexbolt-m8x40: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x40.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x40.stl) — ISO 4017 M8 × 40 hex head, 13 AF × 5.3 head, thread as plain cylinder
- hexbolt-m8x50: [STEP](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x50.step) · [STL](https://xemstudio.com/files/hardware/hex-head-screws-metric/hexbolt-m8x50.stl) — ISO 4017 M8 × 50 hex head, 13 AF × 5.3 head, thread as plain cylinder

## Questions

**How big is an M5 hex head?**

8 mm across flats, 3.5 mm high, 9.2 mm across corners (ISO 4017). A pocket that holds it is 8 AF × 3.5 deep.

**How big is an M8 hex head?**

13 mm across flats, 5.3 mm high, 15.0 mm across corners (ISO 4017).

**Why put the bolt head in a hex pocket?**

The pocket stops the bolt turning, so the nut on the other side can be tightened with one wrench.

## Fits with

- [Hex nuts, M2–M8 (ISO 4032)](https://xemstudio.com/objects/hex-nuts-metric/)
- [Flat washers, M2–M8 (ISO 7089)](https://xemstudio.com/objects/flat-washers-metric/)
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/)
- [Tri-clamp clamp, two-bolt: every flange size ½ to 4 in](https://xemstudio.com/objects/tri-clamp-clamps/)