# Set screw, flat point (ISO 4026 / DIN 913)

Hexagon socket set screw (grub screw) with flat point, metric coarse thread, M3 to M12, length l from d up. Presets cover
the common catalogue sizes (M3 × 3, M5 × 8, ...).

## Geometry

Envelope for assemblies:

- plain cylinder at the nominal thread diameter **d**, overall length **l** (`length`); the thread is not modelled;
- hexagon socket at one end, key size **s** (nominal), depth **t min** for the length (see below), flat bottom;
- flat point of diameter **dp max** at the other end, chamfered at 45° from d.

The socket end is on the XY plane at the origin, the screw along -Z.

## Parameters

| Parameter | Meaning |
|---|---|
| `size` | Thread size, M3 to M12 |
| `length` | Nominal length l, overall, mm; at least d |
| `material` | `steel` (property class 45H, black oxide), `stainless-a2`, `stainless-a4` (ISO 3506-3) |

## Source

ISO 4026:2003, *Hexagon socket set screws with flat point*, Table 1, p. 3: d, dp max, s (nominal), t min. Read from
the official preview <https://cdn.standards.iteh.ai/samples/36431/f53ced64ab1946679bd80f0a0e6cac63/ISO-4026-2003.pdf>
and checked against DIN EN ISO 4026:2004-05 on fasten.it ("reproduced by permission of DIN",
<https://fasten.it/en/Norms/Norm/DIN%20EN%20ISO%204026>, short-length column). DIN 913 is the same screw.
ISO 4026:2026 is now current; its change list (DIN Media, DIN EN ISO 4026:2026) adds M30, changes the dp tolerance
for dp ≤ 1 mm and deletes the masses, so none of the values below changes.

The table gives two t min values: footnote d, for the lengths in the shaded cells, which for M3 to M12 are exactly
l = d (the shortest length of each size); footnote e, for every longer length. The model uses the first for l = d and
the second for l > d. There is no ISO 4026 screw shorter than d, so `length` must be at least d.

| Size | dp max | s | t min (l = d) | t min (l > d) |
|---|---|---|---|---|
| M3 | 2.0 | 1.5 | 1.2 | 2.0 |
| M4 | 2.5 | 2.0 | 1.5 | 2.5 |
| M5 | 3.5 | 2.5 | 2.0 | 3.0 |
| M6 | 4.0 | 3.0 | 2.0 | 3.5 |
| M8 | 5.5 | 4.0 | 3.0 | 5.0 |
| M10 | 7.0 | 5.0 | 4.0 | 6.0 |
| M12 | 8.5 | 6.0 | 4.8 | 8.0 |

Corrected in this audit: the socket depths were not from the table (0.75, 1, 1.25, 1.5, 2, 2.5, 3 = s / 2); they are
now the table's t min. The catalogue's screws shorter than d (M4 × 3, M5 × 3 and × 4, M6 × 3 to × 5) are not ISO 4026
sizes and have no preset.

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