Specifications
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
A286 Cap Screws
A286 cap screws are the general-purpose finished-fastener grade combining a fully formed head and a threaded shank designed to thread into a tapped hole (rather than mate with a nut). TorqBolt manufactures three primary cap screw families: hex cap screws per ASME B18.2.1 / ISO 4014 / 4017, socket head cap screws (SHCS) per ISO 4762 / DIN 912 / NAS 1351 / NAS 6203, and 12-point cap screws per NAS 6603-6620 (aerospace). Sizes M3-M48 metric and #4 to 1-1/2" inch. Heat-treated to ASTM A453 grade 660 Class A for 130 ksi tensile, 95 ksi yield. Cap screws are distinguished from machine screws by their finished head (cold-headed, not stamped) and from bolts by their intended use (thread into tapped hole, not nut). See parent A286 screws, sister socket head cap screws, hex bolts, NAS bolts, and the canonical chemical composition + heat treatment.
About A286 Cap Screws
A286 cap screws span three head styles: external hex (ASME B18.2.1 / ISO 4014), internal hex socket (ISO 4762 / DIN 912 / NAS 1351), and external 12-point bi-hex (NAS 6603). The defining feature is the precision-formed head designed for permanent threaded-hole installation — used in tapped holes in housings, blocks, casings, and structural members rather than nut-and-bolt joints. Each cap screw is cold-headed from A286 bar (AMS 5731), thread-rolled, then solution-treated 1650 °F + aged 1325 °F per AMS 5737. Hardness 277-302 HBW (29-32 HRC). Magnetic permeability < 1.005. Cap screws are typically supplied with full-thread shank (no unthreaded grip section) — distinguishes them from bolts which often have partial thread.
A286 Cap Screw Head Patterns & Standards
TorqBolt produces A286 cap screws in five primary configurations:
- Hex cap screw (ASME B18.2.1) — External hex head — wrenched across-flats. Full-thread shank. ASME B18.2.1 inch (1/4-2-1/2 inch) and ISO 4017 metric (M5-M64). Standard general-purpose cap screw.
- Heavy hex cap screw (ASME B18.2.1) — Thicker hex head than standard — for high-preload applications where head shear margin matters. Common in petrochemical and structural assemblies.
- Socket head cap screw (ISO 4762 / DIN 912 / NAS 1351) — Cylindrical head, internal hex socket — for compact joints with limited wrench clearance. M3-M48 / #4-1-1/2 inch. The dominant aerospace cap screw.
- 12-point cap screw (NAS 6603-6620) — External bi-hex 12-point drive — high-torque transmission with reduced under-head height. Aerospace compressor and turbine bolting.
- Hex flange cap screw (DIN 6921 / ISO 4162) — Integral flange under hex head spreads bearing pressure — eliminates separate washer. Common on automotive turbocharger and exhaust-manifold bolting.
A286 Cap Screw Sizes & Reference
| Size | Hex cap (ASME B18.2.1) | SHCS (ISO 4762) | 12-point (NAS 6603) | Pitch (coarse) | Min. tensile (kN) |
|---|---|---|---|---|---|
| M5 | ✓ | ✓ | — | 0.8 | 12.7 |
| M6 | ✓ | ✓ | ✓ | 1.0 | 18.0 |
| M8 | ✓ | ✓ | ✓ | 1.25 | 32.7 |
| M10 | ✓ | ✓ | ✓ | 1.5 | 51.9 |
| M12 | ✓ | ✓ | ✓ | 1.75 | 75.5 |
| M16 | ✓ | ✓ | ✓ | 2.0 | 140 |
| M20 | ✓ | ✓ | ✓ | 2.5 | 219 |
| M24 | ✓ | — | ✓ | 3.0 | 316 |
| M30 | ✓ | — | — | 3.5 | 502 |
| M48 | ✓ | — | — | 5.0 | 1,318 |
A286 Cap Screws Manufacturing Process
Every a286 cap screws TorqBolt ships traces back to a vacuum-induction-melted plus vacuum-arc-remelted (VIM-VAR) ingot meeting AMS 5731 / 5732 chemistry. The complete process route:
- VIM-VAR melt sourcing: Bar to AMS 5731 / 5732 chemistry per ASTM A453 grade 660. AS9100D for aerospace lots.
- Cold heading (sizes ≤ M16): Multi-station bolt-maker forms the head pattern (hex external, hex socket, or 12-point) in one cycle. Aerospace lots use vacuum-degassed bar.
- Hot heading (sizes ≥ M18): Heated to 1050 °C, upset in die-press for M18-M48 — cold-heading force impractical at large sizes.
- Hex socket cold-forging (SHCS): Hex socket forged in head-stroke per ISO 2936 — depth ≈ 0.5 × head height.
- 12-point machining (aerospace): 12-point bi-hex drive 5-axis machined post-heading for NAS 6603 aerospace cap screws — geometry cannot be cold-headed at large sizes.
- Thread rolling: Cylindrical or flat-die rolling — Class 6g metric / 3A inch (commercial) or 4g6g / Class 3A (MIL-S-8879 aerospace). Rolled threads provide 30-40 % higher fatigue strength.
- Solution treatment: Vacuum heat-treat 1650 °F (899 °C) per AMS 5737 / ASTM A453 Class A. 1 hour per inch, oil-quench.
- Precipitation aging: 1325 °F (718 °C) for 16 hours, air-cool. Hardness 277-302 HBW post-aging. Aerospace ±5 °C control.
- Passivation per ASTM A967: Pickle + HNO₃ rinse + passivate Type II. Optional silver / nickel anti-galling for above-540 °C service.
A286 Cap Screws Inspection & Certification
Each lot ships with a signed inspection certificate. Aerospace lots default to AS9102 FAI reporting under our AS9100D AQMS coverage. Industrial orders default to EN 10204 type 3.1. Variant-specific inspection scope:
- 100 % thread-gauge GO/NO-GO per applicable standard.
- 100 % hex socket dimension check (SHCS) or hex AF (hex cap) or 12-point check (NAS 6603).
- Hardness traverse 4-point Vickers per heat-treat batch.
- Magnetic permeability < 1.005 per ASTM A342 on every aerospace coil.
- LPI per ASTM E1417 Class 1 on aerospace lots.
- Tensile coupon from each heat per ASTM E8.
- AS9102 first-article on aerospace lots; EN 10204 3.1 commercial.
- Salt-spray ASTM B117 96-hour pass for passivated lots.
A286 Cap Screws Torque & Assembly Practice
A286 cap screws torque to 75 % of room-temperature 0.2 % yield for static joints, 60 % for cycling joints. Common torque values: M6 hex cap 8 N·m oil / 6 N·m anti-seize; M10 hex cap 35 N·m oil / 25 N·m anti-seize; M16 hex cap 280 N·m oil / 180 N·m anti-seize; M24 hex cap 980 N·m oil / 620 N·m anti-seize. SHCS variants use Allen key; never apply final torque with ball-end driver. Above 540 °C apply nickel anti-seize per AS5272 to threads. ASME PCC-1 covers torque-vs-tension methods for high-temperature bolted joints.
A286 Cap Screw Applications by Industry
Cap screws thread into tapped holes — applications:
- Aerospace engine accessory mounting: NAS 1351 SHCS and NAS 6603 12-point cap screws on jet-engine accessory gearbox attach, fuel-pump mounting, sensor brackets. A286 jet engine fasteners.
- Industrial gas turbines: Hex cap and SHCS on Siemens / GE / Mitsubishi gas-turbine combustor liner attachment, casing covers, exhaust diffuser bolting. A286 gas turbine applications.
- Automotive turbocharger: M6-M12 hex flange cap screws (DIN 6921) on Garrett, BorgWarner, IHI turbocharger waste-gates and manifold flanges. 600-700 °C cyclic.
- Defence airframe: MS 90725 / MS 90726 hex cap screws on F-15, F-16, F-22, F-35 structural and engine attach lugs.
- Industrial machinery housings: ISO 4762 SHCS on machine-tool housing covers, electrical enclosures, hydraulic manifolds — flush or recessed mount preferred.
- Marine diesel / LNG: MAN B&W, Wärtsilä, MTU diesel engines use M10-M24 hex cap screws on exhaust valve seats, turbocharger mounting, fuel-injection.
Governing Standards & Material Specifications
Every A286 fastener is released against the applicable industry standard. EN 10204 type 3.1 mill certificates ship with every order. See the consolidated A286 AMS / ASTM specifications hub.
| Authority | Specification | Coverage |
|---|---|---|
| ASTM | A453 grade 660 Cl. A/B/C/D | High-temperature bolting material |
| ASTM | A638 grade 660 Type 1/2 | Forged bolting stock |
| AMS | 5731 | Bar / forging — solution-treated |
| AMS | 5732 | Bar / forging — solution-treated and aged |
| AMS | 5737 | Bar — sol-treated and aged (precision) |
| UNS | S66286 | Material designation |
| DIN | 1.4980 / X5NiCrTiMoVB25-15-2 | European designation |
| EN | 10204 3.1 / 3.2 | Mill / third-party-witness certification |
A286 Cap Screws vs Alternative Materials
Engineers compare A286 against three alternatives: A286 vs Inconel 718, A286 vs 17-4 PH, and A286 vs Waspaloy. Within the 540-700 °C service envelope A286 is the dominant cost-performance choice for non-magnetic, oxidation-resistant bolting. See A286 equivalent grades.
How to Specify A286 Cap Screws
A complete a286 cap screws callout should include all eight elements: material spec, heat-treatment condition, dimensional standard, size, thread tolerance class, surface finish, marking, inspection certificate. Example callout:
Hex cap screw, ASME B18.2.1, A286 / UNS S66286, ASTM A453 grade 660 Class A, ST+A, M16 × 2.0 × 80 mm full thread, 6g, passivated, head-stamped ‘A286’ + lot, EN 10204 3.1.
A286 Cap Screws — Frequently Asked Questions
What is the difference between an A286 cap screw and an A286 bolt?
Cap screw: threaded full-length shank, finished head, designed to thread into a tapped hole. Bolt: typically partial-thread shank with unthreaded grip section, designed to mate with a nut. In modern aerospace and ASME usage the terms are often interchangeable; older ANSI / IFI standards distinguish strictly. See A286 hex bolts for partial-thread bolts.
What is the difference between a cap screw and a machine screw?
Cap screw: cold-headed (forged) head, full mechanical strength rating (130 ksi tensile for grade 660 Class A), used for primary bolting. Machine screw: stamped or screw-machine head, lower-strength general-purpose, used for light-load assembly. Machine screws are typically size #4-#10 only; cap screws span #4 to 2-1/2 inch.
Are A286 cap screws magnetic?
No. Magnetic permeability < 1.005 verified on every aerospace lot per ASTM A342. Suitable for instrumentation, MRI, magnetometer, and electromagnetic-sensitive applications.
What thread tolerance for an A286 cap screw?
Commercial 6g (metric) / 2A (inch) — default. Aerospace MIL-S-8879 Class 3A — required for fatigue-critical NAS 1351 / 6603 acceptance. Specify on drawing per application.
Can A286 cap screws be re-used?
Industrial / commercial: yes, multiple cycles permitted with thread inspection and documented torque history. Aerospace primary structure: NO — single-use only per OEM SRM.
What's the difference between hex cap screw and socket head cap screw?
Hex cap: external hex head wrenched across flats — needs wrench clearance. SHCS: cylindrical head with internal hex socket (Allen drive) — fits flush or recessed. SHCS is the dominant aerospace style; hex cap is the dominant industrial style.
What head marking on an A286 cap screw?
Per ASTM F788 (TorqBolt convention): head-stamped 'A286' + 'GR 660' for ASTM A453 traceability + lot + manufacturer 'TB'. Aerospace NAS lots add NAS part number (e.g. 'NAS 1351-N6').
What's the longest A286 cap screw available?
Hex cap (ASME B18.2.1): up to 600 mm in M5-M48. SHCS (ISO 4762): up to 200 mm in M3-M16, 300 mm in M20-M48. 12-point NAS 6603: up to 4-inch in #4-1 inch. Custom-drawing parts longer.
Can A286 cap screws replace stainless 18-8 cap screws?
For high-temperature (>425 °C), corrosion-resistant, non-magnetic, or precipitation-hardening service — yes. For ambient-temperature general industrial — A286 is over-spec at 4-5× the cost of 18-8 stainless. Use A286 only when the application requires its specific properties.
Why TorqBolt for A286 Cap Screws
Three reasons aerospace and gas-turbine OEMs place a286 cap screws orders with us:
- Vertically integrated supply — VIM-VAR melt, in-house cold heading + thread rolling + vacuum heat-treatment.
- Aerospace AQMS — AS9100D-certified factory in Mumbai with published quality manual.
- Lead time discipline — 4-6 weeks standard, 8-12 weeks aerospace custom.
30+ years of fastener-manufacturing track record. Active certifications cover ISO 9001:2015, AS9100D AQMS, PED 2014/68/EU and NORSOK M-650 QTR.
Recent A286 Cap Screws Order Patterns
Recurring cap-screw orders cover ISO 4762 SHCS for aerospace accessory gearbox attach, ASME B18.2.1 hex cap on petrochemical heat-exchanger flanges, NAS 6603 12-point cap screws on jet-engine compressor discs, and DIN 6921 hex flange cap screws on automotive turbocharger.
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