← Bolts
AN178-13
AN178 close tolerance hex head bolt (AN173 THRU AN186)
| Head / form | Hex head, close tolerance |
|---|---|
| Diameter / thread / size | .5000-20 UNF-3A, shank (A dia) .4991-.4986" |
| Grip / length / thickness | grip .688" (±.016), length 1.469" (+.031 -.010 as printed) (AN173 THRU AN186 Rev. 7 sheet 3, Table II) |
| Material / finish | Non-corrosion resistant steel (no material letter) |
| Reference confidence | high |
| Source | AN173 THRU AN186 Rev. 7 (1990-04-09, Distribution A), sheets 1 to 4; AN173 THRU AN186 Rev. 7 Amendment 1 ↗ |
Head / form source: AN173 THRU AN186 Rev. 7 sheet 1 (figure and Table I)
Source notes and limits
- Drilling: no H, no A: drilled shank only (sheet example AN6-10, "SHANK ONLY DRILLED") (AN173 THRU AN186 Rev. 7 sheet 2, note 6).
- Rated strength, STEEL column (AN173 THRU AN186 Rev. 7 sheet 1, Table I cont'd): ultimate tensile at root dia 18,500 lb, yield tensile at root dia 14,190 lb, single shear at full dia 14,700 lb.
- Head mark: "MARK ALL BOLTS WITH A TRIANGLE TO DENOTE CLOSE TOLERANCE BOLT" (sheet 1 figure).
- FAA AC 43.13-1B para 7-44 CAUTION (pages 7-9, 7-10): "Caution must be exercised in the use of close-tolerance bolts for all critical applications, such as landing gear, control systems, and helicopter rotary controls. Do not substitute for close-tolerance fasteners without specific instructions from the aircraft manufacturer or the FAA."
- No cancellation or supersession notice for AN173 THRU AN186 was found in the public sources read (everyspec lists Rev. 7 and Amendment 1 only).
Reference only: the controlling drawing, its process spec and the manufacturer's installation instructions govern. How to use these answers