# Round tube (EN 10305-1 / EN 10220 sizes)

Round tube at any outside diameter, wall thickness and length. Presets cover the catalogue's generic round tubes, each
mapped to a standard tube size.

## Geometry

A hollow cylinder of outside diameter **D** (`diameter`) and wall thickness **T** (`wall`), bore D − 2T, length **l**
(`length`); its axis along +Z, one end face on the XY plane centred on the origin. Dimensions are nominal: the
standards' tolerances are not modelled.

## Parameters

| Parameter | Meaning |
|---|---|
| `diameter` | Outside diameter D, mm |
| `wall` | Wall thickness T, mm (less than D / 2) |
| `length` | Length l, mm |
| `material` | `steel` (E235, EN 10305-1), `stainless-304` (1.4301), `aluminium-6061` (6061-T6) |

## Sources

- EN 10305-1:2002 (BS EN 10305-1:2002, incl. Corrigendum 1), *Steel tubes for precision applications — Technical
  delivery conditions — Part 1: Seamless cold drawn tubes*, **Table 5 "Sizes and tolerances"**, pages 13–14
  (copy consulted: https://www.fushunsteeltube.com/wp-content/uploads/2020/12/EN10305-part1-Steel-tubes-for-precision-applications-Seamless-cold-drawn-tubes.pdf).
  Cross-checked with Mannesmann Precision Tubes' delivery programme "according to EN 10305-1 and EN 10305-2",
  pages 1–2 (https://www.mannesmann.com/fileadmin/footage/MEDIA/gesellschaften/mannesmann/documents/products/MPT_Abmessungsprogramm_Nahtlose_gezogene_und_geschweisste_gezogene_Praezisionsstahlrohre.pdf),
  which agrees on every size below.
- EN 10220:2002 (BS EN 10220:2002), *Seamless and welded steel tubes — Dimensions and masses per unit length*,
  **Table 1**, page 6 (copy consulted: https://www.haopipe.com/upLoad/news/month_1603/201603120241356601.pdf): OD 16
  (series 2) × 1.6, 0.568 kg/m. EN 10305-1 Table 5 has no 1.6 mm wall, so this one size comes from EN 10220.

| D × T (mm) | Bore (mm) | Standard, table | Tolerance on D |
|---|---|---|---|
| 6 × 1 | 4 | EN 10305-1 Table 5 | ±0.08 |
| 8 × 1 | 6 | EN 10305-1 Table 5 | ±0.08 |
| 10 × 1 | 8 | EN 10305-1 Table 5 | ±0.08 |
| 12 × 1.2 | 9.6 | EN 10305-1 Table 5 | ±0.08 |
| 16 × 1.6 | 12.8 | EN 10220 Table 1 | – |
| 20 × 2 | 16 | EN 10305-1 Table 5 | ±0.08 |
| 25 × 2.5 | 20 | EN 10305-1 Table 5 | ±0.08 |

The catalogue entries give only the outside diameter and the length. Each diameter is mapped to the standard section
whose wall the entry's own reference model has (checked privately by its volume; a match only, nothing taken from it).

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