What Tolerances Can CNC Machining Achieve?

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What Tolerances Can CNC Machining Achieve?

Last updated on Oct 01, 2026

CNC machining can achieve a wide range of tolerances, from conventional ±0.1 mm to precision levels of ±0.01 mm. The achievable accuracy is not determined by a single factor; it depends on the combined effect of part geometry, material, process planning, machine condition, and inspection methods.

Typical Tolerance Ranges

Conventional Machining: ±0.05 mm to ±0.1 mm. Suitable for most general mechanical structural parts, housings, brackets, and similar components (supported by Justway).

Precision Machining: ±0.01 mm to ±0.02 mm. Common for automotive components, precision molds, and robotic structural parts (supported by Justway).

Ultra-Precision Machining: ±0.001 mm to ±0.005 mm. Typically required for critical aerospace components, medical implants, and optical instruments (currently not supported by Justway).

Key Influencing Factors

Machine Tools and Process Planning: Five-axis machines are better suited for complex surfaces and can reduce setup errors caused by multiple clamping operations. However, three-axis machines with dedicated fixtures may deliver more stable results for simpler geometries. Separating roughing and finishing operations is critical for stress relief and dimensional stability.

Material and Fixturing: A material’s thermal expansion coefficient and internal stress can affect dimensional stability. Improper fixturing that causes deformation or vibration is one of the main reasons for out-of-tolerance results.

Environment and Inspection: A temperature-controlled workshop, such as 20°C ±0.5°C, is essential for maintaining micron-level accuracy. Final accuracy should be verified with precision inspection equipment such as a CMM, rather than relying solely on the machine tool’s nominal accuracy.

Practical Recommendations

Apply Tolerances Reasonably: Specify tight tolerances only on mating surfaces, sealing surfaces, and locating features. Non-critical dimensions should be relaxed to help control cost.

Clarify Inspection Requirements: State inspection methods and applicable standards on the drawing, such as ISO 2768-m or GD&T geometric tolerances, to avoid disputes during delivery.

Provide Complete Information: Supply Justway with 3D models, 2D drawings, material specifications, intended application, and key functional requirements. This helps generate a more accurate process plan and tolerance commitment.

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What Tolerances Can CNC Machining Achieve?

Typical Tolerance Ranges

Key Influencing Factors

Practical Recommendations