CN Standards For Rolled Aluminium
Differences Between BS & CN Standards
- For those familiar with the old BS1470 it is useful to highlight where the new CN standards differ:
- Chemical Compositions – No Change.
- Alloy Numbering System – No Change.
- Temper Designations for Heat Treatable Alloys – A new wider range of special tempers having up to four digits after the T have been introduced for non- standard applications (e.g. T6151).
- Temper Designations for Non Heat Treatable Alloys – No change to existing tempers but a more comprehensive definition of how tempers are achieved.
- Mechanical Properties – Similar but not identical. Also, 0.2% Proof Stress must now be quoted on test certificates.
- Thickness Tolerances – Considerably tighter for alloys
- 1050A & 3103. To reflect manufacturing difficulty the tolerances for alloys 5251, 5083 & 6082 are now wider than this, although still a little tighter than in BS1470.
- Length and Width Tolerances – These tend to be tighter and are now all on the plus side (i.e. minus zero).
- Flatness Tolerances – These are considerably tighter.
Alloy Groups
Please note that thickness tolerances for cold rolled material vary according to alloy, with the alloys falling into two groups as shown below.
Aluminium Alloy Groups
| Alloy Group |
| Alloy Group I |
| 1080A, 1070A, 1050A, 1200 |
| 3003, 3005, 3103, 3105 |
| 4006, 4007 |
| 5005, 5050 |
| 8011A |
| Alloy Group II |
| 2014, 2017A, 2024 |
| 3004 |
| 5040, 5049, 8053, 5086, 5251, 5052, 5154A, 5454, 5754, 5182, |
| 6061, 6082 |
| 7020, 7021, 7022, 7075 |
Thickness Tolerances
Please note that thickness tolerances for cold rolled material vary according to alloy, with the alloys falling into two groups as shown above.
The thickness tolerances also vary according to the width of the material as shown in the tables below.
Cold Rolled Sheet & Strip - Group I
| Thickness (mm) | Tolerance (mm) +/- | Tolerance (mm) +/- | Tolerance (mm) +/- |
| Group I 1000mm Wide | Group I 1250mm Wide | Group I 1500mm Wide | |
| 0.20 to 0.40 | 0.02 | 0.04 | 0.05 |
| 0.41 to 0.50 | 0.03 | 0.04 | 0.05 |
| 0.51 to 0.60 | 0.03 | 0.05 | 0.06 |
| 0.61 to 0.80 | 0.03 | 0.06 | 0.07 |
| 0.81 to 10.0 | 0.04 | 0.06 | 0.08 |
| 1.10 to 1.20 | 0.04 | 0.07 | 0.09 |
| 1.21 to 1.50 | 0.05 | 0.09 | 0.10 |
| 1.51 to 1.80 | 0.06 | 0.10 | 0.11 |
| 1.80 to 2.00 | 0.06 | 0.11 | 0.12 |
| 2.00 to 2.50 | 0.07 | 0.12 | 0.13 |
| 2.60 to 3.00 | 0.08 | 0.13 | 0.15 |
| 3.10 to 3.50 | 0.10 | 0.15 | 0.17 |
Cold Rolled Sheet & Strip - Group II
| Thickness (mm) | Tolerance (mm) +/- | Tolerance (mm) +/- | Tolerance (mm) +/- |
| Group II 1000mm Wide | Group II 1250mm Wide | Group II 1500mm Wide | |
| 0.20 to 0.40 | 0.03 | 0.05 | 0.06 |
| 0.41 to 0.50 | 0.03 | 0.05 | 0.06 |
| 0.51 to 0.60 | 0.04 | 0.06 | 0.07 |
| 0.61 to 0.80 | 0.04 | 0.07 | 0.08 |
| 0.81 to 1.00 | 0.05 | 0.08 | 0.09 |
| 1.10 to 1.20 | 0.05 | 0.09 | 0.10 |
| 1.21 to 1.50 | 0.07 | 0.11 | 0.12 |
| 1.51 to 1.80 | 0.08 | 0.12 | 0.13 |
| 1.81 to 2.00 | 0.09 | 0.13 | 0.14 |
| 2.10 to 2.50 | 0.10 | 0.14 | 0.15 |
| 2.60 to 3.00 | 0.11 | 0.15 | 0.17 |
| 3.10 to 3.50 | 0.12 | 0.17 | 0.19 |
Cold Rolled Sheet & Strip - Group I/II
| Thickness (mm) | Tolerance (mm) +/- | Tolerance (mm) +/- | Tolerance (mm) +/- |
| Group I/II 1000mm Wide | Group I/II 1250mm Wide | Group I/II 1500mm Wide | |
| 3.60 to 4.00 | 0.15 | 0.20 | 0.22 |
| 4.10 to 5.00 | 0.18 | 0.22 | 0.24 |
| 5.10 to 6.00 | 0.20 | 0.24 | 0.25 |
| 6.10 to 8.00 | 0.24 | 0.30 | 0.31 |
| 8.10 to 10.0 | 0.27 | 0.33 | 0.36 |
| 10.1 to 12.0 | 0.32 | 0.38 | 0.40 |
| 12.1 to 15.0 | 0.36 | 0.42 | 0.43 |
| 15.1 to 20.0 | 0.38 | 0.44 | 0.46 |
| 21.0 to 25.0 | 0.40 | 0.46 | 0.48 |
| 26.0 to 30.0 | 0.45 | 0.50 | 0.53 |
| 31.0 to 40.0 | 0.50 | 0.55 | 0.58 |
| 41.0 to 50.0 | 0.55 | 0.60 | 0.63 |
Hot Rolled Plate
| Thickness (mm) | Tolerance (mm) +/- | Tolerance (mm) +/- |
| 1250mm Wide | 1500mm Wide | |
| 2.50 to 4.00 | 0.28 | 0.28 |
| 4.10 to 5.00 | 0.30 | 0.30 |
| 5.10 to 6.00 | 0.32 | 0.32 |
| 6.10 to 8.00 | 0.35 | 0.40 |
| 8.10 to 10.0 | 0.45 | 0.50 |
| 10.1 to 15.0 | 0.50 | 0.60 |
| 15.1 to 20.0 | 0.60 | 0.70 |
| 21.0 to 30.0 | 0.65 | 0.75 |
| 31.0 to 40.0 | 0.75 | 0.85 |
| 41.0 to 50.0 | 0.90 | 1.00 |
| 51.0 to 60.0 | 1.10 | 1.20 |
| 61.0 to 80.0 | 1.40 | 1.50 |
| 81.0 to 100 | 1.70 | 1.80 |
| 101 to 150 | 2.10 | 2.20 |
| 151 to 220 | 2.50 | 2.60 |
| 221 to 350 | 2.80 | 2.90 |
| 351 to 400 | 3.50 | 3.70 |
Length Tolerances
| Thickness (mm) | Hot Rolled EN485-3 (-0mm) Plus: | Cold Rolled EN 485-4 (-0mm) Plus: |
| 0.20 to 0.30 | 8.0mm | 6.0mm |
| 3.00 to 6.00 | 8.0mm | 8.0mm |
| 6.00 to 12.0 | 8.0mm | 10.0mm |
| 12.0 to 50.0 | 9.0mm | - |
| Over 50.0 | 9.0mm | - |
Width Tolerances
| Thickness (mm) | Hot Rolled EN485-3 (-0mm) Plus: | Cold Rolled EN 485-4 (-0mm) Plus: |
| 0.20 to 3.00 | - | 3.0mm |
| 3.10 to 6.00 | 7.0mm | 4.0mm |
| 6.10 to 12.0 | 7.0mm | 5.0mm |
| 12.1 to 50.0 | 8.0mm | - |
| 51.0 to 200 | 8.0mm | - |
| 201 to 400 | 11.0mm | - |
| Applies to widths 1001mm to 2000mm | Applies to widths 501mm to 1250mm |
Flatness Tolerances
| Product | Thickness (mm) | Max Deviation over 2500mm Length | Max Deviation over 1250mm Width |
| Cold Rolled | 0.50 to 3.00 | 10.0mm | 5.00mm |
| 3.00 to 6.00 | 7.50mm | 3.75mm | |
| Hot Rolled | 6.00 to 200 | 5.00mm | 2.50mm |
