Every dimension on a drawing has a tolerance, stated or not. The usual approach is a general tolerance in the title block, such as ISO 2768-m, plus tighter tolerances only on functional features.
ISO 2768-1 general tolerances for linear dimensions
Class f (fine) and class m (medium) are the classes most used for machined parts:
- Over 0.5 up to 3 mm: f ±0.05 / m ±0.1
- Over 3 up to 6 mm: f ±0.05 / m ±0.1
- Over 6 up to 30 mm: f ±0.1 / m ±0.2
- Over 30 up to 120 mm: f ±0.15 / m ±0.3
- Over 120 up to 400 mm: f ±0.2 / m ±0.5
- Over 400 up to 1000 mm: f ±0.3 / m ±0.8
When to call out tighter tolerances
Bearing seats, press fits, locating holes, sealing faces and mating diameters usually need specific tolerances or ISO fits (for example H7/g6). Cosmetic and clearance features rarely do.
Tolerances and cost
Tighter tolerances need slower finishing passes, more checking and sometimes extra operations. Applying them only where function needs them is the simplest way to reduce part cost.
We machine metal parts to a tolerance of 0.02 mm. Mark critical tolerances on your drawing and we will review them with you.
Chi Xin Technology is a CNC machine shop in Nantun District, Taichung, Taiwan, founded in 2022. We run 5+ CNC machines — 4.5-axis CNC machining centers and CNC lathes — and mainly machine aluminum alloys and alloy steel, with a metal tolerance of 0.02 mm. We also offer wire EDM and surface finishing including anodizing, and we export to customers in Europe and North America.
Frequently asked questions
What general tolerance should I use?
ISO 2768-m suits most machined parts; ISO 2768-f is used for more precise parts. Add specific tolerances on functional features.
What tolerance can you hold?
We machine metal parts to 0.02 mm. Mark critical tolerances on your drawing and we will review them with you.
