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MS21250-16056 12-Point Flange Bolt — 180 KSI, 1.0000-12, 3.500" Grip
MS21250-16056 12-Point Flange Bolt — 180 KSI, 1.0000-12, 3.500" Grip
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The MS21250-16056 is a high-strength 12-point external-wrenching flange bolt designed for tension-critical aerospace structures — airframe joints, engine mounts, rotor and control-system connections where 180 ksi tensile performance and positive wrenching engagement are required. Its flanged 12-point head delivers high clamp force in confined spaces where a standard hex cannot develop sufficient torque.
Specifications
| Part Number | MS21250-16056 (supersedes to NASM21250-16056) |
| Thread | 1.0000-12 UNJF-3A per MIL-S-8879 |
| Grip Length | 3.500 in (±.010) |
| Overall Length | 5.124 in (±.015) |
| Head Diameter (A) | 1.615–1.625 in |
| Shank Diameter (B) | 0.9980–0.9990 in |
| Flange Diameter (W) | 1.0625 in |
| Head Height (H) | 0.923 in |
| Thread Length (T) | 1.479 in ref |
| Ultimate Tensile Strength | 180,000–200,000 psi |
| Double Shear Strength | 169,600 lbf |
| Tensile Strength (min) | 126,000 lbf |
| Material | AISI 4340 alloy steel (4140 / 8740 / 6150 alternates) |
| Hardness | HRC 39–43 |
| Finish | Cadmium plate + chromate per QQ-P-416 Type II Class 2 |
| Head Marking | MS21250 + manufacturer's code |
| Procurement Spec | MIL-B-8831 |
Datasheet & Compliance
| FSC | 5306 (Bolts) |
| NSN | 5306-01-550-3447 |
| ECCN | EAR99 (no license required for standard export) |
| Schedule B | 7318.15.8085 |
| Net Weight | ≈ 1.478 lb (670 g) per piece |
| MOQ | None — order from 1 pc |
Manufacturer certifications (CoC + mill report + dimensional report) ship FREE with every lot.
Alternatives & Related Parts
- No drilled-head variant in this diameter group (H drilling available on dash 02–12 only)
- Same diameter group, other grip lengths: 3.500"–5.125" grips available
- Current standard: NASM21250 (military adoption of MS21250; fully interchangeable)
- Not for new design after 4 Dec 1980 per the standard — replacement-in-kind only; we support all legacy fleet demand.
Lead Time
Made to order — ships in 4 weeks. Raw material (AISI 4340 bar) is stocked at our Kunshan plant; every lot is machined, heat-treated, plated and inspected to order. No stockouts, no minimums on standard sizes.
Quality Documentation
Every lot ships with: Certificate of Conformance (CoC) · mill material report (heat-lot traceable) · full dimensional inspection report · First Article Inspection (FAI) on request. 100% thread and plating verification per MIL-B-8831.
Shipping & Duties — DDP
Free express shipping on orders of $300 or more; a flat $49.99 courier charge applies to smaller orders (FedEx/DHL, 3–7 days worldwide after the 4-week production lead time). US import duty and Section 301 tariffs are included in our prices — delivered duty paid, no customs surprises. Larger programs (>500 pcs or >$5,000): request a quote for FOB terms and volume pricing.