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 Socket Head Cap Screws
A286 socket head cap screws (commonly abbreviated SHCS, also called Allen cap screws, internal hex bolts, or cylindrical head cap screws) are the dominant internal-drive A286 fastener for compact and limited-clearance joints. TorqBolt manufactures A286 SHCS to ISO 4762, DIN 912, ASME B18.3 (inch series), NAS 1351 / NAS 1352 / NAS 6203 (aerospace), and MIL-DTL-23054 (military). The cylindrical head with hex-socket internal drive permits flush or recessed mounting where wrench-across-flats clearance is unavailable. Sizes M3-M48 metric, #4 to 1-1/2" inch, heat-treated to ASTM A453 grade 660 Class A for 130 ksi tensile / 95 ksi yield. See parent A286 screws overview, related A286 bolts, button head screws, flat head screws, and the canonical A286 chemical composition + heat treatment pages.
About A286 Socket Head Cap Screws
TorqBolt cold-heads or machines A286 socket head cap screws from A286 bar (AMS 5731 / 5732 / 5737) with the cylindrical head profile and internal hex socket forged in a single press operation for sizes ≤ M16, or 5-axis machined for larger sizes and aerospace precision parts. Hex socket size follows ISO 2936: M3 = 2.5 mm hex key, M4 = 3 mm, M5 = 4 mm, M6 = 5 mm, M8 = 6 mm, M10 = 8 mm, M12 = 10 mm, M16 = 14 mm, M20 = 17 mm. Threads are rolled (not cut) post-aging to maximise fatigue strength. Each lot ships with EN 10204 3.1 mill certificate; aerospace lots default to AS9102 first-article inspection per AS9100D AQMS.
A286 Socket Head Cap Screw Head Patterns & Drive
TorqBolt produces five socket-drive head profiles on A286 substrate:
- Standard socket head cap (ISO 4762 / DIN 912), Cylindrical head with hex socket, the canonical SHCS. Head height ≈ nominal diameter, head-to-shank fillet 0.4 mm minimum.
- Low head socket cap (ISO 7984 / DIN 6912), Reduced head height (~0.6× nominal) for limited axial clearance. Lower preload capacity, use with knurled hex bit.
- Aerospace socket head cap (NAS 1351 / NAS 6203), AMS 5732 material default, MIL-S-8879 thread tolerance, magnetic permeability < 1.005, full lot certification.
- 12-point flange (NAS 1351 12-point), Bi-hex external drive replaces hex socket on aerospace high-torque joints, used on engine-mount and structural-attachment bolts.
- Extended-shank shoulder bolt (ASME B18.3), Unthreaded precision shoulder + threaded end, pivot pin or guide bolt. See A286 shoulder bolts.
A286 SHCS Sizes & Hex Key Reference
| Metric size | Pitch | Hex key | Head ⌀ | Head height | Min. tensile (N) |
|---|---|---|---|---|---|
| M3 | 0.5 | 2.5 mm | 5.5 mm | 3.0 mm | 2,500 |
| M4 | 0.7 | 3 mm | 7.0 mm | 4.0 mm | 4,500 |
| M5 | 0.8 | 4 mm | 8.5 mm | 5.0 mm | 7,200 |
| M6 | 1.0 | 5 mm | 10.0 mm | 6.0 mm | 10,200 |
| M8 | 1.25 | 6 mm | 13.0 mm | 8.0 mm | 18,600 |
| M10 | 1.5 | 8 mm | 16.0 mm | 10.0 mm | 29,400 |
| M12 | 1.75 | 10 mm | 18.0 mm | 12.0 mm | 42,800 |
| M16 | 2.0 | 14 mm | 24.0 mm | 16.0 mm | 79,800 |
| M20 | 2.5 | 17 mm | 30.0 mm | 20.0 mm | 124,500 |
A286 Socket Head Cap Screws Manufacturing Process
Every a286 socket head 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 is variant-specific:
- VIM-VAR melt + bar: A286 bar (AMS 5731 / 5732) sourced VIM-VAR with controlled grain size ASTM 5-7. Diameter selection: bar OD = head ⌀ × 1.05 to allow head-trim flash.
- Cold heading (sizes ≤ M16): Multi-station cold heading press: extrusion (shank ⌀) → cone form → cylindrical head trim → hex socket forming punch in a single press cycle. Hex socket depth ≈ 0.5 × head height.
- Machining (sizes > M16): Bar turned on 5-axis CNC: shank turned to thread blank diameter, head OD turned to ISO 4762 spec, hex socket milled or broached. Used for M20-M48 and aerospace precision NAS 6203.
- Thread rolling: Threads rolled post-heading using cylindrical or flat dies. Class 6g metric / 3A inch, MIL-S-8879 thread tolerance for aerospace NAS 6203 lots. Rolled threads provide 30-40 % higher fatigue strength vs cut.
- Solution treatment: Vacuum heat-treat 1650 °F (899 °C, AMS 5737 / Cl. A) or 1800 °F (982 °C, AMS 5732 / Cl. B) for 1 h per inch, oil-quench.
- Precipitation aging: Re-heat 1325 °F (718 °C) for 16 hours, air-cool. Develops gamma-prime Ni₃(Ti,Al) precipitates. Hex socket dimension verified post-aging, aging causes 0.05 % linear shrinkage.
- Hex socket dimension check: 100 % go/no-go gauge of hex socket per ISO 2936, checks both across-flats and corner depth. Critical: mis-sized socket fails Allen-key engagement at field assembly.
- Surface finish: Pickle / passivate per ASTM A967 type II. Optional silver or nickel anti-galling coat for above-540 °C service per AS5272.
- Aerospace marking: Aerospace SHCS head-stamp 'A286' + lot + manufacturer 'TB' per NAS 1351 / 6203. Permanent ink marking for non-aerospace lots.
A286 Socket Head Cap Screws Inspection & Certification
Each lot ships with a signed inspection certificate. Aerospace orders default to AS9100D first-article reporting per AS9102 on the first part of any new drawing or revision. Industrial orders default to EN 10204 type 3.1; sour-service and offshore orders step up to type 3.2 with third-party witness present at heat-treat release and tensile testing. Variant-specific inspection scope:
- 100 % hex socket gauge per ISO 2936, both across-flats and corner-to-corner.
- 100 % thread-gauge GO/NO-GO per ANSI/ASME B1.1 (inch) or ISO 1502 (metric).
- Hardness traverse on each heat-treat lot, 4-point Vickers HV per ASTM E384.
- Magnetic permeability < 1.005 per ASTM A342 on every aerospace lot.
- LPI per ASTM E1417 Class 1 on aerospace lots, surface defect detection ≥ 0.10 mm.
- Tensile coupon from each heat, yield, tensile, elongation per ASTM E8.
- AS9102 first-article inspection on the first SHCS of any new drawing or revision for AS9100D AQMS lots.
- Salt-spray testing per ASTM B117 for passivated lots (96 h pass per A967).
TorqBolt’s quality file maintains the audited NORSOK M-650 QTR for A286 fastener manufacture, renewed every 5 years. Customer-witnessed source surveillance is welcomed.
A286 Socket Head Cap Screws Torque & Assembly Practice
Socket head cap screws torque per the same A286 grade-660 limits as hex bolts (75 % of yield for room-temperature applications, 60 % for cycling joints). Hex-socket drive limits applied torque vs hex external, Allen key shear strength is the typical failure mode at sizes ≤ M5. Use a calibrated torque wrench with hex-socket bit; never use a ball-end Allen driver for final torque (causes localised stress in socket corner). Torque values: M6 = 8 N·m oil / 6 N·m anti-seize; M10 = 35 N·m oil / 25 N·m anti-seize; M16 = 180 N·m oil / 130 N·m anti-seize. Above 540 °C apply nickel anti-seize to the threads and to the head-bearing face under the SHCS head.
A286 SHCS Applications by Industry
Socket head cap screws are the high-strength choice when wrench access is limited. Primary uses:
- Aerospace engine mounts: NAS 1351 / 6203 SHCS attach engine accessories (gearboxes, sensors, fuel manifolds) where standard hex wrench cannot reach. A286 jet engine fasteners overview.
- Industrial gas turbines: Combustor liner attachment, nozzle ring retention, exhaust diffuser bolting. The compact head profile clears adjacent ductwork.
- Aerospace structural: Wing-spar internal bolting, fuselage frame attachment where flush or recessed mounting is required. Thread tolerance MIL-S-8879 standard.
- Precision instrumentation: Non-magnetic A286 SHCS used in MRI scanners, mass spectrometers, particle accelerators, magnetometers. Permeability < 1.005.
- Cryogenic equipment: LNG valve actuators, cryogenic pump flanges, hydrogen storage vessel internals. Retains 85 % of RT toughness at -196 °C.
- Semiconductor / vacuum: UHV chamber internal bolting where corrosion + non-magnetic + low outgassing all required.
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; type 3.2 third-party-witnessed inspection is available for nuclear, offshore and customer-mandated source-surveillance contracts. See the consolidated A286 AMS / ASTM specifications hub for full spec scope.
| 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, solution-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 |
| NACE | MR0175 / ISO 15156-3 | Sour-service hardness limit ≤ HRC 35 |
A286 Socket Head Cap Screws vs Alternative Materials
When selecting a fastener material engineers compare A286 against three alternatives: A286 vs Inconel 718 (top-end performance, 3× cost), A286 vs 17-4 PH (cheaper but limited to 315 °C), and A286 vs Waspaloy (sustained service > 700 °C). Across the 540-700 °C operating window, A286 delivers the lowest cost per MPa of retained preload. See the consolidated A286 equivalent grades reference for full alloy alternatives.
How to Specify A286 Socket Head Cap Screws
A complete a286 socket head cap screws callout on a drawing or purchase order should include all eight elements: material spec, heat-treatment condition, dimensional standard, size, thread tolerance class, surface finish, marking, inspection certificate. Example complete callout:
Socket head cap screw, AMS 5732, ST+A, ISO 4762, M10 × 1.5 × 50 mm, 6g, MIL-S-8879 (aerospace), passivated, head-marked ‘A286’ + lot, magnetic permeability < 1.005, EN 10204 3.1.
A286 Socket Head Cap Screws, Frequently Asked Questions
What is the difference between A286 socket head cap screw and A286 hex bolt?
Socket head cap screws have a cylindrical head with internal hex socket (Allen drive). Hex bolts have a six-flat external hex head wrenched across flats. SHCS allows recessed/flush mounting; hex bolts need wrench clearance. Both supply the same A286 mechanical strength.
What hex key fits an A286 M6 socket cap screw?
5 mm hex key (Allen wrench). Standard hex socket sizes per ISO 2936: M3=2.5mm, M4=3mm, M5=4mm, M6=5mm, M8=6mm, M10=8mm, M12=10mm, M16=14mm, M20=17mm.
What is the difference between ISO 4762 and DIN 912 A286 socket cap screws?
Functionally identical, both define metric SHCS dimensions. ISO 4762 is the current international standard; DIN 912 was the German pre-cursor. Modern drawings cite ISO 4762; older European drawings still cite DIN 912. Dimensions are identical for M3-M48.
Can A286 socket head cap screws meet aerospace spec NAS 6203?
Yes, TorqBolt manufactures A286 NAS 6203 SHCS to AMS 5732 material, MIL-S-8879 thread tolerance, magnetic permeability < 1.005, with full lot traceability and AS9102 first-article inspection per AS9100D AQMS.
What is the proof load of an M10 A286 SHCS?
29.4 kN (6,610 lbf) per ASTM A453 grade 660 Class A, calculated from 130 ksi tensile × M10 stress area (58 mm²). Yield-load 21.4 kN at 95 ksi yield. Use 75 % of yield as design preload for static joints.
Are A286 SHCS suitable for cryogenic service?
Yes, A286 SHCS retain 85 % of room-temperature toughness at -196 °C. Used in LNG valve actuators, hydrogen storage internal hardware, and aerospace cryogenic engine components. Confirm Charpy V-notch ≥ 27 J at service temperature for safety-critical joints.
Can A286 SHCS replace 18-8 stainless steel SHCS?
For high-temperature service, yes, A286 SHCS hold strength to 700 °C where 304/316 stainless drops below useful strength at 425 °C. For room-temperature service A286 is over-spec and 4-5× the cost of 18-8 stainless; use A286 only when temperature, magnetic, or strength requirements justify it.
What thread tolerance applies to aerospace A286 SHCS?
MIL-S-8879 / ASME B1.13M Class 3A for inch threads, 4g6g for metric. These are tighter than commercial 2A / 6g, required for aerospace fatigue performance and NAS 6203 / NAS 1351 acceptance.
What is the head-marking on an A286 NAS 6203 SHCS?
Head-stamp 'A286' + lot number + manufacturer ID 'TB' per NAS 6203 marking convention. 12-point flange version (NAS 6603) uses the same stamp. Stamp depth 0.05-0.10 mm, raised or recessed per drawing.
Why TorqBolt for A286 Socket Head Cap Screws
Three reasons aerospace and gas-turbine OEMs place a286 socket head cap screws orders with us:
- Vertically integrated supply, VIM-VAR melt sourcing from approved AMS-conforming mills, in-house cold heading + thread rolling + vacuum heat-treatment. No outsourced critical step.
- Aerospace AQMS, AS9100D-certified factory in Mumbai with a published quality manual covering A286 fastener-specific failure-mode analysis (preload retention, hydrogen embrittlement, thread fatigue, galling).
- Lead time discipline, 4-6 weeks for ASTM A453 grade 660 standard sizes, 8-12 weeks for custom-drawing aerospace parts. No surprises.
30+ years in fastener manufacture; no MOQ on stocked DIN / ISO patterns; ISO 9001:2015 + AS9100D + PED 2014/68/EU + NORSOK M-650 QTR all current. Lot traceability runs from VIM-VAR melt heat number through finished-part packaging.
Recent A286 Socket Head Cap Screws Order Patterns
TorqBolt's recurring SHCS order categories: gas-turbine combustor liner attachment (M6-M10), aircraft engine accessory gearbox bolting (NAS 6203), MRI scanner internal hardware (M4-M6 non-magnetic verified), and turbocharger waste-gate retention (M8).
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