# Hex head screw (ISO 4017 / DIN 933)

Hexagon head screw threaded up to the head, metric coarse thread, M1.6 to M36, at any length. Presets cover the
common catalogue sizes (M6 × 20, M8 × 40, ...).

## Geometry

Envelope for assemblies and clearance checks:

- hexagon head, width across flats **s** (nominal), height **k** (nominal), sharp corners (across corners
  s / cos 30°, the largest the head can be); two flats parallel to the X axis;
- plain shank at the nominal thread diameter **d**, length **l** (`length`); the thread is not modelled.

The head's bearing face is on the XY plane at the origin, the head above it, the shank along -Z.

## Parameters

| Parameter | Meaning |
|---|---|
| `size` | Thread size, M1.6 to M36 |
| `length` | Nominal length l under the head, mm |
| `material` | `steel` (property class 8.8, zinc plated), `stainless-a2`, `stainless-a4` (ISO 3506-1) |

## Source

ISO 4017:2022, *Fasteners — Hexagon head screws — Product grades A and B*, Tables 1 to 3, pp. 3-5: d, s (nominal =
max), k (nominal), read from the official preview
(<https://cdn.standards.iteh.ai/samples/72585/1179998ddd594550a909d6e13c416f3e/ISO-4017-2022.pdf>; M30 and M36 are
product grade B, Table 3). The same values in ISO 4017:2011, Table 1
(<https://fpg-co.com/Standards/ISO%204017-2011%20Hexagon%20head%20screws%20%E2%80%94%20Product%20grades%20A%20and%20B.pdf>)
and, for M1.6 to M6, the ISO 4017:2014 preview. fasten.it's DIN EN ISO 4017:2014 page gives k 19 and 23 for M30 and
M36, which are DIN 933 heights and contradict its own k min (18.28, 22.08); the ISO tables' 18.7 and 22.5 are used.
DIN 933 uses the same s for these sizes except M10 (17), M12 (19), M14 (22) and M22; this recipe follows ISO 4017.

| Size | s | k |
|---|---|---|
| M1.6 | 3.2 | 1.1 |
| M2 | 4.0 | 1.4 |
| M2.5 | 5.0 | 1.7 |
| M3 | 5.5 | 2.0 |
| M4 | 7.0 | 2.8 |
| M5 | 8.0 | 3.5 |
| M6 | 10.0 | 4.0 |
| M8 | 13.0 | 5.3 |
| M10 | 16.0 | 6.4 |
| M12 | 18.0 | 7.5 |
| M14 | 21.0 | 8.8 |
| M16 | 24.0 | 10.0 |
| M20 | 30.0 | 12.5 |
| M24 | 36.0 | 15.0 |
| M30 | 46.0 | 18.7 |
| M36 | 55.0 | 22.5 |

Preset list: sizes and lengths of the step.parts catalogue (MIT), see `library/NOTICE.md`.