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Total rivet length from grip length

Aviation Mechanic Airframe (AMA) practice question 17 of 20 on Metallic Structures. ACS element AM.II.A.K7 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA 1/8 inch diameter rivet is to be installed where the combined thickness of the material is 0.125 inch. What total rivet length is required?

  1. A1/4 inch
  2. B3/8 inch, the next longer rivet
  3. C5/16 inch
Show the answer and explanation

Correct answer: C. 5/16 inch

  • A — incorrect This allows only 0.125 inch beyond the grip, which is one diameter rather than the one and one-half diameters needed to form a proper shop head.
  • B — incorrect Three-eighths inch leaves two full diameters of shank beyond the grip, more than a properly formed shop head requires.
  • C — correct Total length is grip length plus one and one-half diameters: 0.125 inch plus 0.1875 inch equals 0.3125 inch, which is 5/16 inch.

BACKGROUND

Before a rivet can be selected, the mechanic must know the grip length, which is the combined thickness of the materials being joined. The total length of the rivet equals that grip length plus the amount of shank needed to form a proper shop head. The handbook states that a properly formed shop head equals one and a half times the diameter of the rivet shank, giving the relationship total length equals grip length plus shop head allowance. The size of the formed head is the visual standard by which a proper installation is judged, so getting the length right is what makes a correct shop head possible at all. Where rivets pass completely through tubular members, special rules apply, and rivets of the same alloy number as the material being riveted should be selected whenever possible.

STUDY TIP

Do the shop head allowance in decimals, then convert to the nearest rivet length in sixteenths of an inch, since rivet length is called out in sixteenths.

KEY POINTS

  • Total rivet length equals grip length plus the shop head allowance.
  • A properly formed shop head equals one and one-half times the shank diameter.
  • 0.125 inch grip with a 1/8 inch rivet needs 0.3125 inch, or 5/16 inch, of total length.

SOURCES

  • sources/ama-airframe/ch04.txt "Rivet Length"
  • sources/ama-airframe/ch04.txt "Solid Shank Rivet"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.