Standards
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
NAS6308 tension 12-point bolts
NAS6308 is the 1/2" body diameter member of the NAS6300-series 12-point external-drive aerospace tension cap-screw family (the -8 dash number indicates 8/16" = 1/2" body). It is widely used in primary airframe structural fastening, wing-spar attachment fittings, primary engine mount hardware and main-rotor mast bolting on rotorcraft because the 1/2" shank delivers the joint clamp force needed for primary aircraft structure. NAS6308 is typically produced to 160 ksi tensile in A286 (UNS S66286), and is one of the most commonly specified primary-structural dash-sizes in the NAS6300 family.
TorqBolt manufactures NAS6308 cap-screws in A286, AISI 8740 chromoly heat-treated, Inconel 718, MP35N and Custom 465 to AS9100D Rev D and ISO 9001:2015 quality systems. Each cap-screw head carries the struck tB manufacturer ligature plus the alloy grade marking, and every lot ships with a mill test report (MTC 3.1 standard, MTC 3.2 critical with third-party witness inspection of chemistry, hardness, tensile, and dimensional records).
Common Alloys for NAS6308
| Alloy | Tensile | Service envelope |
|---|---|---|
| A286 (UNS S66286) | 160 ksi | up to 700 °C |
| Inconel 718 (UNS N07718) | 180 ksi | up to 700 °C, jet-engine |
| AISI 8740 chromoly | up to 220 ksi (HT) | standard high-strength |
| Ti-6Al-4V (Grade 5) | 130 ksi | 56% lighter than steel |
UNJ-3A External Thread Dimensions (Common 12-Point Bolt Sizes)
Per SAE AS8879 (controlled-root-radius UNJ external thread). 12-point aerospace bolts under MS21250, NAS1351, AS3216, NAS6303 to NAS6320 are produced to UNJ-3A external thread tolerances. Root radius 0.150 P to 0.180 P (where P = pitch) for fatigue resistance, this is the difference vs standard UN-3A and the reason aerospace specifies UNJ.
| Nominal | TPI | Pitch P (mm) | Major Dia Min (mm) | Major Dia Max (mm) | Pitch Dia Min (mm) | Pitch Dia Max (mm) | Minor Dia Min (mm) | Minor Dia Max (mm) |
|---|---|---|---|---|---|---|---|---|
| 1/4-28 UNJF-3A | 28 | 0.907 | 6.297 | 6.350 | 5.706 | 5.770 | 5.156 | 5.296 |
| 5/16-24 UNJF-3A | 24 | 1.058 | 7.875 | 7.938 | 7.185 | 7.249 | 6.553 | 6.711 |
| 3/8-24 UNJF-3A | 24 | 1.058 | 9.462 | 9.525 | 8.773 | 8.840 | 8.139 | 8.298 |
| 7/16-20 UNJF-3A | 20 | 1.270 | 11.051 | 11.113 | 10.227 | 10.297 | 9.467 | 9.652 |
| 1/2-20 UNJF-3A | 20 | 1.270 | 12.638 | 12.700 | 11.815 | 11.887 | 11.051 | 11.243 |
| 9/16-18 UNJF-3A | 18 | 1.411 | 14.225 | 14.288 | 13.310 | 13.385 | 12.466 | 12.673 |
| 5/8-18 UNJF-3A | 18 | 1.411 | 15.812 | 15.875 | 14.897 | 14.973 | 14.054 | 14.262 |
| 3/4-16 UNJF-3A | 16 | 1.588 | 18.991 | 19.050 | 17.961 | 18.040 | 17.018 | 17.246 |
| 7/8-14 UNJF-3A | 14 | 1.814 | 22.166 | 22.225 | 21.001 | 21.085 | 19.926 | 20.181 |
| 1-12 UNJF-3A | 12 | 2.117 | 25.336 | 25.400 | 23.974 | 24.064 | 22.717 | 22.985 |
| 1 1/4-12 UNJF-3A | 12 | 2.117 | 31.687 | 31.750 | 30.328 | 30.418 | 29.072 | 29.343 |
| 1 1/2-12 UNJF-3A | 12 | 2.117 | 38.037 | 38.100 | 36.678 | 36.768 | 35.422 | 35.693 |
| 1 15/16-12 UNJF-3A | 12 | 2.117 | 49.149 | 49.213 | 47.791 | 47.886 | 46.535 | 46.812 |
| 2-12 UNJF-3A | 12 | 2.117 | 50.737 | 50.800 | 49.378 | 49.473 | 48.122 | 48.399 |
Internal thread (UNJ-3B, mating nut) tolerances and metric M-J equivalents available on request. Send drawing or spec callout to info@torqbolt.com.
Request a Quote
Send drawing or PO line referencing NAS6308 to info@torqbolt.com or call +91-22-66157017.
Related aerospace specs
For broader 12-point aerospace specification context, see also the parent aerospace fasteners hub and the full 12-point catalog, plus sibling specs:
- NAS1351, close-tolerance 12-point external-wrenching
- MS21250, 160 ksi 12-point external-drive aerospace bolt
- AS3216, 180 ksi superalloy 12-point for turbine section
- MIL-DTL-7838, legacy mil-spec, replaced by NAS series
- NAS6303, 3/16" body NAS 6300-series tension cap-screw
- NAS6304, 1/4" body NAS 6300-series tension cap-screw
- NAS6305, 5/16" body NAS 6300-series tension cap-screw
- NAS6310, 5/8" body NAS 6300-series tension cap-screw
- NAS6312, 3/4" body NAS 6300-series tension cap-screw
- NAS6315, 15/16" body NAS 6300-series tension cap-screw
- NAS6320, 1-1/4" body NAS 6300-series tension cap-screw
- DIN 12-Point, European metric 12-point M5 to M30, grade 12.9
Frequently Asked Questions
What diameter is a NAS6308 bolt?
NAS6308 covers 1/2-inch (0.500) nominal diameter close-tolerance 12-point bolts to NAS6300 series geometry, sized for primary structural attachment in airframe and propulsion bracketing.
What is the shear capacity of a NAS6308 bolt?
A286 NAS6308 bolts at 160 ksi tensile and 95 ksi shear (per AMS 5731) deliver approximately 18,650 pounds single-shear ultimate capacity on the 0.500-inch nominal shank, with shear strength linearly related to tensile via the 0.6 shear factor.
What surface treatments apply to NAS6308?
Standard A286 NAS6308 is passivated per AMS 2700 for corrosion resistance; alloy-steel variants receive cadmium plating per AMS-QQ-P-416 Type II Class 2 or IVD aluminum per AMS 2750 for galvanic compatibility.
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