A practical guide to standard aluminum extrusion tolerances - the dimensional limits engineers should specify, why they vary by profile size and alloy, and how to avoid over-tolerancing that inflates cost.
Understanding the tolerance limits of extruded aluminum is one of the first things an engineer should master before sending a design to production. This guide explains the standard tolerances, what affects them, and how to specify them correctly.
What Are Aluminum Extrusion Tolerances?
Extrusion tolerances are the allowable dimensional variations in a finished aluminum profile. Because aluminum flows through a die under heat and pressure, every dimension carries a small deviation. Tolerances define how much variation is acceptable while keeping the part functional.
Standard Tolerance Ranges
| Dimension Type | Typical Tolerance |
|---|---|
| Cross-section width | +/- 0.2 mm to +/- 0.5 mm |
| Wall thickness | +/- 0.1 mm to +/- 0.3 mm |
| Straightness | 0.3 mm per 1000 mm |
| Cut length | +/- 1 mm to +/- 3 mm |
| Angle | +/- 1 degree |
These ranges follow common industry standards, including GB/T 5237 (China), EN 755 (Europe), and AA standards (USA). The exact tolerance depends on the dimension size and profile complexity.
What Affects Tolerance
Several factors determine how tight a tolerance can be achieved:
- Profile size โ larger dimensions naturally carry larger deviations
- Wall thickness โ thin walls are harder to hold to tight tolerances
- Profile complexity โ more intricate shapes are more difficult to control
- Alloy โ 6063 flows more easily and holds tighter tolerances on thin walls
- Die condition โ a new die holds tighter tolerances than a worn one
How to Specify Tolerances Correctly
Follow these steps to avoid costly mistakes:
- Specify only the critical dimensions โ over-tolerancing increases cost without adding value
- Reference a standard โ state which standard (GB/T 5237, EN 755, AA) applies to your drawing
- Allow a realistic range โ talk to your supplier about what is achievable before locking the drawing
- Consider secondary machining โ if you need very tight tolerances, CNC machining after extrusion is the reliable path
Get the Right Tolerances for Your Project
SYHARVEST produces aluminum extrusions to GB/T 5237 and EN 755 standards, with CNC machining available for dimensions requiring tighter control. Send us your drawings and we will advise on achievable tolerances and the most cost-effective process.
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