Resources · Tolerances
Aluminum extrusion & CNC tolerances
What tolerance you can expect, and where to spend effort: extrusion per EN 755-9, machining per ISO 2768, with notes on when to machine critical features.
Extrusion tolerances (EN 755-9)
Extruded profiles are held to EN 755-9 general tolerances — typically fractions of a millimeter on dimensions, with straightness and twist also specified. Tighter bands are possible with post-extrusion machining.
| Feature | Typical (EN 755-9) |
|---|---|
| Cross-section dimension | ±0.1 to ±0.3 mm (size-dependent) |
| Wall thickness | ±0.1 to ±0.2 mm |
| Straightness | per standard length class |
| Twist | per standard length class |
CNC machining tolerances (ISO 2768)
Machined features follow ISO 2768 (medium, or fine on request). Positioning can reach ±0.01 mm on our centers.
| Feature | Typical |
|---|---|
| Linear machined dim | ±0.05 to ±0.1 mm (ISO 2768-m) |
| Positioning | ±0.01 mm |
| Hole / thread | H7 / 6H typical |
| Surface (Ra) | 0.8 achievable |
How to specify
- Let extrusion hold general shape; machine only critical faces, holes and threads.
- Mark true datums so inspection is unambiguous.
- Ask for fine class (ISO 2768-f) only where needed — it costs more.
Unsure what to call out?
Send the drawing — we flag which dims need machining vs extrusion tolerance.