Every part is made to some tolerance, whether you specify it or not. When your drawing does not state one, we use the general standard ISO 2768-1 class m (medium) for linear and angular dimensions and ISO 2768-2 class K for geometric tolerances.
What we routinely deliver
- Linear dimensions: ±0.10 mm (±0.004 in) by default; down to ±0.025 mm (±0.001 in) on dimensions specified on the drawing.
- Diameters and fits: per the class on the drawing (h7, H7, g6…).
- Threads: class 6H/6g metric and 2B/2A unified, unless stated otherwise.
- FDM 3D printing: ±0.20 mm or ±0.2% of the dimension, whichever is greater.
Tight tolerances only where they matter
Mark on the drawing only what is truly functional: mating holes, fits, sealing faces, center distances. Leave the rest to the general tolerance. Tightening the whole part raises cost without adding function: more finishing passes, more inspection and more risk of rejection.
Surface finish
By default parts are delivered as machined: Ra ≤ 3.2 µm (125 µin) on milled faces and Ra ≤ 1.6 µm (63 µin) on turned faces. A specific Ra goes on the drawing.
Resources
ISO 2768 tolerance chart, ISO 286 fit chart, surface finish chart and our Manufacturing Standards.