FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesEasy
A technician is selecting rivets to repair a stressed skin panel and finds a rivet with a raised dot stamped on the manufactured head. This head marking identifies the rivet as which alloy, and what special handling does it require?
- A7075-T6 aluminum alloy; must be annealed before driving
- B2117-T4 aluminum alloy; may be driven directly from stock
- C1100 pure aluminum; no special handling required
- D2024-T3 aluminum alloy; must be stored in a freezer until just before driving
Show answer & explanationAnswer & explanation
Correct answer: D. 2024-T3 aluminum alloy; must be stored in a freezer until just before driving
A raised dot on the rivet head identifies a 2024-T3 aluminum alloy rivet (often called an 'ice box' rivet). Because 2024-T3 age-hardens quickly at room temperature after heat treatment, it is kept refrigerated to delay precipitation hardening so it stays soft enough to be driven without cracking.
Why the other options are wrong
- A. 7075-T6 is marked with a raised triangle, not a raised dot.
- B. 2117-T4 rivets use a recessed dot, not a raised dot, and are stable at room temperature.
- C. 1100 rivets are unmarked, not marked with a dot.
Rivet Head Identification Codes
Raised or recessed symbols stamped on a rivet's manufactured head identify its aluminum alloy composition per AC 43.13-1B.
- No marking = 1100/3003 pure aluminum
- Recessed dot = 2117-T4 (AD), usable at room temperature
- Raised dot = 2024-T3 (DD), must be refrigerated until driven
Memory trick: 'Dot Up = Freeze it, Dot In = Use it'