FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesMedium
While sorting hardware, a technician finds a bolt with two raised dashes stamped on the head. According to standard bolt head marking conventions, this bolt is made of which material and requires what precaution?
- ATitanium alloy; requires no special handling
- BMonel; used only in firewall applications
- CAluminum alloy; should not be reused if removed from a torqued installation
- DCorrosion-resistant steel; may be reused indefinitely
Show answer & explanationAnswer & explanation
Correct answer: C. Aluminum alloy; should not be reused if removed from a torqued installation
Two raised dashes on a bolt head identify an AN aluminum-alloy bolt. These bolts are softer and more prone to thread damage and fatigue, so once removed from a torqued application they generally should not be reinstalled or reused in critical applications.
Why the other options are wrong
- A. Titanium bolts are not part of the standard AN raised-dash marking system.
- B. Monel bolts use a different identification symbol, not two dashes.
- D. Corrosion-resistant steel bolts use a different marking, not two dashes.
Bolt Head Marking System
AN bolt heads carry raised or recessed symbols identifying material and grade, allowing technicians to verify correct bolt use without disassembly.
- No marking = commercial-grade bolt, not for aircraft primary structure
- One raised dash = AN standard steel bolt
- Two raised dashes = AN aluminum-alloy bolt
Memory trick: 'Double dash = light aluminum flash'