Standard Machining Tolerances
What Are Machining Tolerances?
Machining tolerances define the acceptable range of variation in a finished part’s dimensions. No manufacturing process produces components that are 100% exact, so tolerances ensure that even with slight deviations, a part will still fit and function as intended.
For example, a shaft designed to fit into a bearing must be machined within a specific tolerance range. Too large, and it won’t fit. Too small, and the connection will be loose. Setting the right tolerance is critical for product reliability, safety, and cost-effectiveness.
How Are Tolerances Measured?
Tolerances are typically measured in thousandths of an inch (0.001”) or in microns (µm) for metric applications. Inspection equipment such as calipers, micrometers, and coordinate measuring machines (CMMs) verify these measurements.
Two common ways tolerances are expressed include:
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Bilateral tolerance
Variation allowed in both directions (+/- 0.002”)
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Unilateral tolerance
Variation allowed in only one direction (+0.000” / -0.005”)
Industry Standards for Machining Tolerances
Most industries follow quality standards set by organizations such as:
- ISO 2768 – Defines general tolerances for linear and angular dimensions in metric.
- ASME Y14.5 – U.S. standard for geometric dimensioning and tolerancing (GD&T).
These standards ensure consistency across manufacturers and supply chains, making it possible for parts made in different facilities to work together seamlessly.
Standard Machining Tolerance Ranges
While tolerances vary by material, process, and part geometry, the chart below outlines typical machining tolerance ranges.
| Process | Standard Tolerance (inches) | Standard Tolerance (mils) |
|---|---|---|
| Milling | ±0.005” | ±5 mils |
| Turning | ±0.002” | ±2 mils |
| Drilling | ±0.005” | ±5 mils |
| Grinding | ±0.0005” | ±0.5 mil |
| Laser Cutting | ±0.0005” | ±0.5 mil |
Standard Tolerances vs. Tight Tolerance Cutting
Standard machining tolerances work well for many applications. However, industries such as aerospace, medical devices, and microelectronics often require tighter tolerances for components that demand precision beyond standard machining.
➡ Learn more about tight tolerance laser cutting and how it compares to standard machining tolerances.
Why Tolerances Matter in Manufacturing
- Performance: Ensures components fit and function reliably.
- Interchangeability: Enables parts from different manufacturers to integrate.
- Cost Efficiency: Balances precision needs with production costs.
- Quality Assurance: Reduces errors and defects.
By understanding and applying the correct standard machining tolerances, engineers can optimize both design performance and manufacturability.
FAQs About Standard Machining Tolerances
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A general tolerance of ±0.005” (±0.13 mm) is widely accepted for standard machining unless otherwise specified.
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Not necessarily. Tighter tolerances often increase machining time and cost. The right tolerance depends on the application.
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Yes. Laser cutting can achieve tolerances as tight as ±0.001” (±0.025 mm), depending on material and thickness. See our tight tolerance laser cutting page for details.
Need parts manufactured with precision?
Whether your project requires standard machining tolerances or ultra-tight specifications, our team can help you determine the best approach.