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What Are CNC Machining Tolerances?
CNC machining tolerances refer to the acceptable deviation in a part’s dimensions. Defined as ±X mm or ±X inch, tolerances determine how much a part’s size can differ from its design specifications. Achieving precise tolerances is essential for fit, function, and performance, especially in industries such as aerospace, medical, and robotics.
1. Typical tolerance ranges
General machining tolerances：
✅ General Tolerance:
±0.05mm to ±0.2mm (depending on equipment and process).
✅ High-Precision Machining:
± 0.01mm to ±0.05mm (such as precision molds, aerospace parts).
✅ Ultra-Precision Machining:
± 0.001mm to ±0.005mm (e.g. optics, medical implants).
2. Different materials tolerance
✅ Metallic materials (e.g. aluminum, steel):
General milling/turning: ±0.05mm to ±0.1mm.
High-precision machining (e.g. 5-axis linkage): ± 0.01mm to ±0.02mm.
✅ Plastic materials (e.g. PEEK, nylon):
Normal machining: ± 0.1mm to ±0.2mm.
Precision machining: ±0.05mm to ±0.1mm.
✅ Composites (e.g. carbon fiber):
Tolerances are wide, typically ±0.1mm to ±0.3mm.
3. different processing methods Tolerances
✅ Milling:
Face milling: ±0.05mm to ±0.1mm.
Milling of complex surfaces: ± 0.1mm to ±0.2mm.
✅Turning:
External turning: ± 0.01mm to ±0.05mm.
Internal turning: ±0.02mm to ±0.08mm.
✅Drill:
Normal drilling: ± 0.1mm to ±0.2mm.
Precision drilling (e.g. deep hole drilling for aviation): ± 0.01mm to ±0.05mm.
4.Factors that affect tolerances
✅ Factors of the equipment itself
✅CNC cutting tool factor
✅CNC parts form factor
✅Processing environmental factors
✅Material factors
Our CNC Tolerance Capabilities
We support both ISO 2768-m (medium) and ISO 2768-f (fine) standards. Custom tolerances based on drawings are also accepted.
3. CNC Tolerances by Machining Process
Tolerances of different machining methods
| Process | Typical Tolerance Range |
| Face Milling | ±0.05mm – ±0.1mm |
| Complex Surface Milling | ±0.1mm – ±0.2mm |
| External Turning | ±0.01mm – ±0.05mm |
| Internal Boring | ±0.02mm – ±0.08mm |
| Standard Drilling | ±0.1mm – ±0.2mm |
| Precision Deep Hole Drilling | ±0.01mm – ±0.05mm |
Balancing Cost & Precision
How We Ensure Tolerance Accuracy
Our workshop uses high-precision equipment and quality control systems to ensure your parts meet the required CNC tolerances:
What Influences CNC Machining Tolerances?
Discover The Factors That Affect CNC Machining Tolerances：Machine type, cutting conditions, tool wear, material, and temperature all affect the final tolerance.
Machine Precision
Machine type:
✅ Ordinary CNC machine : The tolerance is usually ±0.05mm to ±0.1mm.
✅ High-precision machine : The tolerance can reach ±0.005mm to ±0.01mm. (Such as five-axis CNC machines, slow wire cutting)
✅ CNC machine spindle accuracy: The spindle radial runout and axial runout will affect the processing accuracy.
✅ CNC machine guide rail accuracy: The guide rail straightness error will be directly reflected in the workpiece size.
Parameter setting
CNC machining parameter setting:
✅Cutting speed: Too high or too low cutting speed may cause tool wear or vibration, increasing tolerance.
✅Feed rate: Too large feed rate will increase surface roughness and affect dimensional accuracy.
✅Cutting depth: Too large cutting depth may cause workpiece deformation, especially thin-walled parts.
Material Properties
CNC Machined Material Properties:
✅ Material hardness: Hard materials (such as quenched steel) wear out quickly and increase tolerances when machining.
✅ Material deformation: Heat treatment or cutting heat can cause material deformation, affecting tolerances.
✅ Material uniformity: Castings or composites may have internal stresses or inhomogeneities, resulting in machining errors.
Machine Parts Size
CNC Parts Workpiece Size & Shape:
✅ Dimensional effect:
The larger the workpiece, the greater the absolute tolerance (e.g. a 1 meter workpiece may have a tolerance of ±0.1 mm, while a 10 cm workpiece has a tolerance of ±0.02 mm).
✅ Shape complexity: Complex curved or deep cavity structures typically have greater tolerances than simple planar or cylindrical structures.
Working Environment
CNC company working environment temperature change:
✅ Thermal expansion: Machines and tools have different coefficients of thermal expansion, which can lead to dimensional deviations.
Aluminum, for example, has a high coefficient of thermal expansion and needs to be processed with temperature compensation in mind.
CNC cutting tools
The tool is an important tool for machining center to carry out cutting processing, and its quality and condition have an important impact on the machining accuracy. For example, problems such as tool wear, edge deformation, and chipping can all affect machining accuracy. At the same time, the selection of geometric parameters (such as edge inclination, rake angle, rear angle, etc.) and cutting parameters (such as cutting speed, feed, cutting depth, etc.) of the tool will also have an impact on the machining accuracy.
Gallary of Tight-Tolerance CNC Parts
We deliver high-accuracy CNC machined components with tolerances from ±0.2mm to as tight as ±0.001mm. Whether you need general machining or ultra-precision components, we have the capabilities to meet your tolerance requirements.
CNC Machining Tolerances – FAQ
Standard CNC machining tolerances are typically ±0.127 mm (±0.005″). For general applications, this tolerance ensures parts fit and function correctly. Tighter tolerances are available for precision machining needs.
High-precision CNC machines can achieve tolerances as tight as ±0.005 mm (±0.0002″). However, achievable tolerances depend on factors like material, machine type, and part geometry.
±0.01mm tolerance means the actual size of the part can vary by 0.01mm above or below the specified dimension. In CNC machining, this level is considered a tight or precision tolerance.
Yes. Materials like plastics may expand or shrink more during machining compared to metals like aluminum or steel, so tolerances may need adjustment based on material behavior.
For aluminum CNC machining, tolerances of ±0.01 mm to ±0.05 mm are typically achievable, depending on part complexity and equipment. Tight tolerances may require precision setups and quality control.
You can, but cost and feasibility depend on the design, material, and machining limits. We recommend practical tolerances where possible.
Yes, tighter tolerances often require additional processes such as slower cutting speeds, multiple passes, special tools, or extra quality checks, which may increase costs and lead time.
We ensure tolerance accuracy through precision machines, skilled operators, calibrated inspection tools, and strict quality control processes. Inspection reports are available upon request.
We follow international standards such as ISO 2768 and ASME Y14.5 for CNC machining tolerances. If your project requires specific compliance, please indicate it in your drawings.
General CNC tolerances (e.g., ±0.1 mm) are suitable for non-critical parts, while precision tolerances (e.g., ±0.01 mm or tighter) are used for high-performance or assembly-critical parts.
Yes, plastics typically have looser tolerances due to flexibility and thermal expansion (e.g., ±0.1mm or more).