What are the two degrees used for countersink rivets?

What are the two degrees used for countersink rivets?

• A. 82 and 100 degrees
• B. 80 and 100 degrees
• C. 82 and 99 degrees
• D. 85 and 100 degrees

Answer: (A)

Countersunk rivets are designed to sit flush with the surface, so the countersink angle must match the head shape of the rivet. In aviation practice, two standard countersink angles are used: 82 degrees and 100 degrees. The 100-degree countersink is the common one for most flush rivets, giving a flat, smooth surface when the rivet head seats correctly. The 82-degree countersink is used for a different rivet head geometry, often from older or specific constructions, where that steeper cone matches the head profile. Using either of these two standard angles ensures the rivet head seats properly and the skin remains flush. Angles like 80, 85, or 99 degrees don’t correspond to the common rivet head geometries, so they’d misfit the head and could leave a nonflush surface or cause deformation.

Countersunk rivets are designed to sit flush with the surface, so the countersink angle must match the head shape of the rivet. In aviation practice, two standard countersink angles are used: 82 degrees and 100 degrees. The 100-degree countersink is the common one for most flush rivets, giving a flat, smooth surface when the rivet head seats correctly. The 82-degree countersink is used for a different rivet head geometry, often from older or specific constructions, where that steeper cone matches the head profile.

Using either of these two standard angles ensures the rivet head seats properly and the skin remains flush. Angles like 80, 85, or 99 degrees don’t correspond to the common rivet head geometries, so they’d misfit the head and could leave a nonflush surface or cause deformation.