If you see a purple rivet on a magnesium aircraft skin (common in older Cessnas, Pipers, or helicopter tail booms), you can safely assume it is a NAS523 rivet. Substituting a blue (2024) or yellow (2017) rivet could lead to catastrophic corrosion within months.
| Dash No. | Diameter (in) | Diameter (mm approx.) | |----------|--------------|------------------------| | 4 | 1/8" (0.125) | 3.18 | | 5 | 5/32" (0.156) | 3.97 | | 6 | 3/16" (0.188) | 4.76 | | 8 | 1/4" (0.250) | 6.35 | | 10 | 5/16" (0.313) | 7.94 | nas523 rivet code pdf
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