FAA Aviation Mechanic Airframe (AMA)Airframe StructuresHard
A technician has driven a 1/8-inch (0.125 in) diameter universal head solid rivet. Using the general rule of thumb from AC 43.13-1B that the driven head diameter should be approximately 1.5 times the shank diameter, what is the minimum acceptable driven head diameter?
- A0.156 inch
- B0.125 inch
- C0.1875 inch
- D0.250 inch
Show answer & explanationAnswer & explanation
Correct answer: C. 0.1875 inch
The driven head diameter should be about 1.5 times the rivet shank diameter: 1.5 × 0.125 in = 0.1875 in. A driven head smaller than this indicates insufficient bucking and an undersized/weak rivet installation.
Why the other options are wrong
- A. 0.156 inch equals only 1.25D, still undersized for an acceptable driven head.
- B. 0.125 inch equals the shank diameter itself, indicating the head was not properly formed.
- D. 0.250 inch equals 2D, which is oversized and may indicate excessive material buildup or a cracked head.
Driven Rivet Head Dimensions
The bucked (driven) head of a solid rivet should measure approximately 1.5 times the shank diameter, with a height of about 0.5 times the shank diameter.
- Driven head diameter ≈ 1.5D
- Driven head height ≈ 0.5D
- Undersized heads indicate weak, understrength rivets
- Oversized/cracked heads indicate overdriving
Memory trick: 1.5 times wide, half as tall — the golden rivet head rule.