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AN4DD21A
Aeronautical Standard Machine Bolt
Description
Airframe Bolt
Specifications
| Country of Origin | USA |
|---|---|
| Fastener Length | 2.141 inches minimum and 2.188 inches maximum |
| Features Provided | Finished head |
| Grip Length | 1.672 inches minimum and 1.703 inches maximum |
| Head Height | 0.140 inches minimum and 0.172 inches maximum |
| Head Style | Hexagon Head |
| Length | 2 3/16 |
| Material | Aluminum |
| Material Specification | Qq-a-200 fed spec single material response or qq-a-225 fed spec single material response or qq-a-430 fed spec single material response |
| Min. Tensile Strength (psi) | 62000 pounds per square inch |
| Surface Treatment | Oxide film and anodize |
| Surface Treatment Specification | Mil-c-5541 mil spec 1st treatment response and mil-a-8625 mil spec 2nd treatment response |
| Thread Class | 3a |
| Thread Diameter | 0.250 |
| Thread Direction | Right-hand |
| Thread Length | 0.438 inches minimum and 0.516 inches maximum |
| Thread Qty | 28 |
| Thread Qty Per Inch (tpi) | 28 |
| Thread Series Designator | UNF |
| Thread Size | 1/4 |
| Weight | 0.01 lb |
| Width Between Flats | 0.428 inches minimum and 0.440 inches maximum |
Other sizes
Parts that share this base number, ordered by size. Always verify the full specification before substituting.
Cross-reference
Similar parts
Parts with matching key dimensions — often from a different standards family. Candidates for comparison only; verify the full specification before substituting.
- AN174-21A AN 1/4-28 · 0.086 in · Hexagon Head · Steel
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Catalog data updated 2026-07-05. Report a data error