# Button head screw (ISO 7380-1)

Hexagon socket button head screw, metric coarse thread, M3 to M16, at any length. Presets cover the common catalogue
sizes (M3 × 6, M5 × 10, ...).

## Geometry

Envelope for assemblies and clearance checks:

- domed head: a spherical cap of diameter **dk max** and height **k max** (the standard's head radius is a reference
  value; the cap through the rim and the top is used);
- hexagon socket, key size **s** (nominal), depth **t min**, flat bottom;
- 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, M3 to M16 |
| `length` | Nominal length l under the head, mm |
| `material` | `steel` (property class 10.9 / 12.9, black oxide), `stainless-a2`, `stainless-a4` (ISO 3506-1) |

## Source

ISO 7380-1:2011, *Button head screws — Part 1: Hexagon socket button head screws*, Table 1, p. 3: d, dk max, k max,
s (nominal), t min, read from the official preview
(<https://cdn.standards.iteh.ai/samples/53671/84df01c5fcce4a91896ac3b0c55ca128/ISO-7380-1-2011.pdf>) and fasten.it's
DIN EN ISO 7380-1:2011-11 (<https://fasten.it/en/Norms/Norm/DIN%20EN%20ISO%207380-1>). The current edition,
ISO 7380-1:2022, Table 1, p. 4
(<https://cdn.standards.iteh.ai/samples/78699/a175805085534f98983d6c8aa583a5b0/ISO-7380-1-2022.pdf>), has the same
dk max, k max, s and t min (it adds t max and changes dw and e, which this model doesn't use).

| Size | dk | k | s | t |
|---|---|---|---|---|
| M3 | 5.7 | 1.65 | 2.0 | 1.04 |
| M4 | 7.6 | 2.2 | 2.5 | 1.3 |
| M5 | 9.5 | 2.75 | 3.0 | 1.56 |
| M6 | 10.5 | 3.3 | 4.0 | 2.08 |
| M8 | 14.0 | 4.4 | 5.0 | 2.6 |
| M10 | 17.5 | 5.5 | 6.0 | 3.12 |
| M12 | 21.0 | 6.6 | 8.0 | 4.16 |
| M16 | 28.0 | 8.8 | 10.0 | 5.2 |

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