FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesMedium
A technician is installing a new structural bolt in a critical airframe location. The bolt is subjected to both shear and tensile loads. Which type of bolt is specifically designed to withstand high shear loads and is commonly identified by its close-tolerance shank and often a shorter grip length?
- AAN standard bolt
- BNAS close-tolerance bolt
- CMS clevis bolt
- DSAE grade 8 bolt
Show answer & explanationAnswer & explanation
Correct answer: B. NAS close-tolerance bolt
NAS (National Aerospace Standard) close-tolerance bolts are specifically designed for applications requiring high shear strength and a precise fit, characterized by their exact shank diameter and often a shorter grip length for optimal shear load transfer.
Why the other options are wrong
- A. AN standard bolts are general-purpose bolts, not specifically designed for high shear with close tolerances.
- C. MS clevis bolts are primarily designed to withstand shear loads only (no tensile) and are used for hinge-type applications, not general structural bolting under combined loads.
- D. SAE grade 8 bolts are automotive specification bolts, not approved for aircraft structural applications and do not necessarily have close tolerances.
NAS Close-Tolerance Bolt
A National Aerospace Standard bolt designed for critical structural applications requiring a precise fit and high shear strength, identified by its exact shank diameter and sometimes a shorter grip length.
- Used where precise alignment and minimal movement are crucial.
- Provides superior shear strength compared to standard AN bolts.
- Requires reaming of the hole to exact size before installation.
Memory trick: NAS bolts are precise, strong, and shear-resistant.