# Low head socket cap screw (DIN 7984)

Hexagon socket head cap screw with low head, metric coarse thread, M3 to M12, at any length. Presets cover the
common catalogue sizes (M3 × 8, M6 × 20, ...).

## Geometry

Envelope for assemblies and clearance checks:

- cylindrical low head, diameter **dk max**, height **k max**;
- 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 M12 |
| `length` | Nominal length l under the head, mm |
| `material` | `steel` (property class 8.8, black oxide), `stainless-a2`, `stainless-a4` (ISO 3506-1) |

## Source

DIN 7984:2009-06, *Hexagon socket head cap screws with low head*, Tabelle 1, pp. 6-7: d, dk max, k max, s
(nominal), t min. Read from a full copy of the standard (<https://tdm-neva.ru/upload/screws/din-7984.pdf>) and checked
against fasten.it's reproduction of DIN 7984 2009-06 / 2021-10 / 2022-03 (<https://fasten.it/en/Norms/Norm/DIN%207984>,
"t nom") and Aspen Fasteners' sheet (<https://www.aspenfasteners.com/content/pdf/Metric_DIN_7984_spec.pdf>, t nominal).
DIN Media's change note for DIN 7984:2022-03 lists no dimensional change since 2009-06, so the values hold for the
current edition.

| Size | dk | k | s | t |
|---|---|---|---|---|
| M3 | 5.5 | 2.0 | 2.0 | 1.38 |
| M4 | 7.0 | 2.8 | 2.5 | 2.18 |
| M5 | 8.5 | 3.5 | 3.0 | 2.58 |
| M6 | 10.0 | 4.0 | 4.0 | 2.88 |
| M8 | 13.0 | 5.0 | 5.0 | 3.65 |
| M10 | 16.0 | 6.0 | 7.0 | 4.35 |
| M12 | 18.0 | 7.0 | 8.0 | 4.85 |

Corrected in this audit: t was the nominal depth (and 4.8 for M12, in no source) under a "t min" label; it is now
the table's t min (1.38, 2.18, 2.58, 2.88, 3.65, 4.35, 4.85).

DIN 7984 starts at M3: the smaller low-head screws some catalogues list have no standard dimensions and are not
included. Preset list: sizes and lengths of the step.parts catalogue (MIT), see `library/NOTICE.md`.