Standard CNC tolerances, when to tighten them and how tolerance choices affect part cost.
(Content in this language is being translated. Showing English version.)
Choosing the right tolerance saves cost. This guide explains standard CNC machining tolerances and when to tighten them.
Standard Tolerances
Unless specified, we hold ISO 2768-m (±0.1mm for small features). Most CNC features can hold ±0.05mm easily; precision machining reaches ±0.01mm and even ±0.005mm with grinding.
When to Tighten Tolerances
Only bearing fits, sealing surfaces and mating interfaces need tight tolerances. Over-tolerancing increases cost by 30-100% due to extra setups, inspection and scrap.
Tolerance and Cost Table
| Tolerance | Relative Cost | Typical Use |
| ±0.1mm | 1.0x | General features |
| ±0.05mm | 1.2x | Assembly fits |
| ±0.01mm | 1.8x | Bearing seats |
| ±0.005mm | 2.5x | Gauge, optics |