What Are CNC Machining Tolerances?
Tolerances define the acceptable range of variation in a part's dimensions. In CNC machining, standard tolerances typically range from ±0.005" (±0.127mm) for general features to ±0.001" (±0.025mm) for precision work.
Common Tolerance Standards
| Class | Tolerance | Application |
|---|---|---|
| Standard | ±0.005" | General features |
| Precision | ±0.002" | Mating surfaces |
| Ultra-precision | ±0.0005" | Optical, aerospace |
Design Tips
- Only specify tight tolerances where functionally necessary — tighter tolerances increase cost.
- Use GD&T (Geometric Dimensioning & Tolerancing) for complex requirements.
- Consider material — metals hold tighter tolerances than plastics.
- Account for thermal expansion in high-precision assemblies.
Conclusion
Specifying the right tolerances is key to balancing cost, quality, and functionality. Contact our engineering team for tolerance recommendations specific to your project.