Hex‑head cap screws, also called hex cap bolts, are externally threaded fasteners with six-sided heads designed for use with a nut or in a tapped hole. They are essential in military, aerospace, automotive, and industrial systems where high torque, alignment precision, and certified grade performance are required.
1. Standards & Military Compliance
Military-grade hex-head cap screws must meet strict specifications such as MIL‑DTL‑1222 standards, and specific MS part numbers including MS35307, MS35308, MS90725, and MS90726. These parts adhere to material, thread, coating, and tensile requirements according to MIL-SPEC, DFARS, and ASME guidelines.
2. Materials, Grades & Mechanical Requirements
- Alloy Steel (Grade 8 or ASTM A490 / A354 Grade BD or BC): High tensile strength—proof strength up to ~830 MPa, tensile to ~1,040–1,500 MPa—usable in high-stress structural applications.
- Stainless Steel (MS35307/35308): High corrosion resistance and medium strength suitable for naval or arctic components.
- Titanium, Nickel Alloys, Monel, Inconel: Used when strength-to-weight, heat resistance, or magnetic compatibility is essential.
3. Thread Precision & Torque Control
Hex‑head cap screws typically feature Class 3 threads (NAS/AN/MS standards) for tight thread engagement and preload predictability. Head markings indicate grade and traceability, and proper torque application enhances fatigue resistance and joint stability—critical under vibration or dynamic stress.
Hex‑Head Cap Screw Class & Application Table
| Specification / Grade | Material & Strength | Typical Application |
|---|---|---|
| MS90725 / MS90726 | Grade 5 carbon steel, cadmium-plated, coarse/fine threads | Structural and chassis assemblies |
| MS35307 / MS35308 | 300‑series stainless, corrosion-resistant; coarse/fine tread | Naval platforms, moisture exposure zones |
| ASTM A354 BD / ASTM A490M | Alloy steel Grade BD; proof 830 MPa; tensile up to 1,040–1,200 MPa | Heavy-duty structural joints, launch equipment |
| Titanium & Nickel Alloy Hex Caps | Weight‑reduced, high strength-to-weight, non-magnetic | Aerospace structures, stealth systems |
| Standard ISO/ANSI Hex Caps | Class 8.8, 10.9 metric grades per ISO 4014/4017 | General industrial and vehicular hardware |
4. Corrosion & Finish Considerations
Military hex caps often incorporate cadmium plating (yellow or clear), zinc-nickel, or other mil-spec coatings for environmental durability. Stainless steel variants may be passivated. These finishes support corrosion resistance, fatigue tolerance, and secure thread performance in extreme conditions.
Why Hex‑Head Cap Screws Matter
- High Torque Capacity: The six-sided head allows maximum torque transfer with ratchets or wrenches, even in tight spaces.
- Precision & Reliability: Certified grades with controlled threads ensure preload accuracy—essential in high-frequency load cycles.
- Traceability: Military-grade screws come with batch documentation, headmark codes, and material certification for quality assurance and audit readiness.
Partner with Metric Bolt for Military-Grade Hex Caps
At Metric Bolt, we supply hex-head cap screws compliant with MIL‑SPEC (MS90725, MS35307, ASTM A490M, ASME B18.2.1, ISO 4014/4017) across materials—steel, stainless, titanium, nickel alloys—with certified finishes and full traceability.
Need hex-head cap screws engineered to mission standards?
Contact Metric Bolt to request certified parts, technical support, or supply chain guidance.
