What tolerances can CNC turning hold?
At FormHub, CNC turning runs to ISO 2768-m as standard, with ±0.025 mm (fijnbewerking) in fine machining and ±0.01 mm na engineering review. Surface roughness: Ra 0.2 – 1.6 µm.
- Tighter tolerances cost money: each step down means slower cutting or printing, extra inspection and a higher scrap rate. Expect roughly +30% for ±0.05 mm and +80% for ±0.01 mm versus standard.
- So tolerance only functional surfaces: fits, sealing faces and datum holes. A drawing where everything is tightly toleranced is the most expensive drawing you can send.
- The instant envelope for CNC turning is Ø300 × 500 mm. Larger parts are quoted via engineering review — we deliberately publish no hard maxima.
Frequently asked questions
- Do I get an inspection report?
- On request we supply a measurement report of the critical dimensions, and a full FAI report if needed. Mention it with the request so it is included in the price.
- What if my drawing states no tolerances?
- We then apply ISO 2768-m as the general tolerance. That is the industry standard and sufficient for most non-mating dimensions.