# V-slot extrusion 20 × 20

A 20 × 20 mm V-slot aluminium extrusion, any length: a V-slot in each face, 0.5 mm outside corner radii and a 4.2 mm
centre bore.

## Geometry

The section is centred on the origin in the XY plane and extruded along +Z by `length`. Each of the four slots (the
same, turned 90°), from the face inwards:

| Feature | mm |
|---|---|
| Outside, square | 20 |
| Outside corner radius | 0.5 |
| Slot width at the face | 9.7 |
| Width between the lip tips (45° V, 1.8 below the face) | 6.1 |
| Lip underside, from the centre (flat out to the undercut wall) | 8.2 |
| Undercut width | 11.0 |
| Undercut wall ends, from the centre (then 45° to the core) | 6.5607 |
| Core face width / from the centre | 5.6786 / 3.9 |
| V notch in the core face, width × depth | 0.4 × 0.2 |
| Centre bore | Ø 4.2 |

Section area 168.01 mm² (0.454 kg/m in 6063).

## Parameters

| Parameter | Meaning |
|---|---|
| `length` | mm |
| `finish` | anodising colour, `clear` or `black` (appearance only) |

## Sources

There is no manufacturer drawing behind this part: **the geometry was measured from the published reference model**
below, on its cross-section at mid-length (exact OCCT section edges), and the recipe re-draws that section in its own
code. Each preset is checked against the model: bounding box within 0.05 mm, volume within 2 %, section area within 2 %
and the section outline within 0.1 mm of the model's.

- **FreeCAD-library**, `Mechanical Parts/Mountings/2020_V-slot_Al_extrusion/2020x50_V_slot_profile-Part.step`
  (commit 2e36ae32), by **hasecilu**; https://github.com/FreeCAD/FreeCAD-library; licensed under
  [CC-BY-3.0](https://creativecommons.org/licenses/by/3.0/) (the library's licence for all its parts). Distributed by
  step.parts as `2020x50_v_slot_profile` (https://www.step.parts/parts/2020x50_v_slot_profile), identical geometry.
  No endorsement by the author or the FreeCAD project is implied.

Simplifications: none beyond the reference model's own (it has no fillets inside the slots and no end threads). The
model is a generic 20 × 20 V-slot; check a specific maker's section (OpenBuilds and others differ slightly) where it
matters.

Presets: the 50 mm reference sample and the catalogue's V-slot lengths (100 to 1500 mm). The catalogue's own models
at those lengths, and its 20 × 40 to 20 × 80 entries, are step.parts' simplified stand-ins (a rectangle with one
rectangular groove per face), not V-slot sections: they are not used, and the length presets are checked against the
reference model's section (area and outline as above, volume = its section area × length). Preset list: from the
step.parts catalogue (MIT), see `library/NOTICE.md`.