bolts › close tolerance bolts
AN175-21
Aeronautical Standard Close Tolerance Bolt
Description
Close Tolerance Bolt
Specifications
| Country of Origin | USA |
|---|---|
| Distance From Head Largest Bearing Surface To Shank Hole Center | 1.531 inches minimum first hole and 1.563 inches maximum first hole |
| Drilling | Drilled Head |
| Fastener Length | 2.203 inches minimum and 2.250 inches maximum |
| Grip | 1 11/16 in |
| Grip Diameter | 0.3112 inches minimum and 0.3117 inches maximum |
| Grip Length | 1.672 inches minimum and 1.704 inches maximum |
| Hardness Rating | 26.0 rockwell c minimum and 32.0 rockwell c maximum |
| Head Height | 0.172 inches minimum and 0.204 inches maximum |
| Head Style | Hexagon Head |
| Head Type | Hexagon |
| Industry Standards/Certification | AN175 |
| Length | 2 1/4, 2 7/32 in |
| Material | Steel |
| Material Specification | Mil-s-6049 mil spec 1st material response or mil-s-6050 mil spec 2nd material response or mil-s-6098 mil spec 3rd material response or ams 6300 assn std 4th material response or mil-s-5626 mil spec 5th material response or mil-s-6758 mil spec 6th material response |
| Min. Tensile Strength (psi) | 125000 pounds per square inch |
| NIIN | 00-180-0473 |
| NSN | 5306-00-180-0473 |
| Shank Unthreaded Hole Diameter | 0.076 inches nominal first hole |
| Surface Finish | 63.0 microinches bearing surface of head, 63.0 microinches grip |
| Surface Treatment | Cadmium and chromate |
| Surface Treatment Specification | Qq-p-416 type 2 class 3 fed spec all treatment responses |
| Thread Class | 3a |
| Thread Diameter | 0.312 |
| Thread Direction | Right-hand |
| Thread Length | 0.499 inches minimum and 0.578 inches maximum |
| Thread Qty | 24 |
| Thread Qty Per Inch (tpi) | 24 |
| Thread Series Designator | UNF |
| Thread Size | 0.3125-24, 1/4 |
| Weight | 0.06 lb |
| Width Between Flats | 0.490 inches minimum and 0.502 inches maximum |
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.
- AN175-21A AN 24.00-24 · 0.086 in · Hexagon Head · Steel
Looking for a specific part? Use the cross-reference lookup.
Catalog data updated 2026-07-05. Report a data error