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 CRES Bolts
A286 CRES bolts — where CRES stands for Corrosion-Resistant Steel, the US aerospace industry shorthand for stainless steels including A286 — are the dominant non-magnetic precipitation-hardening fasteners on US-spec aircraft engine and airframe drawings. TorqBolt manufactures CRES A286 bolts to NAS 1351 / NAS 1352 / NAS 6203 (socket head), NAS 6603-6620 (12-point), MS90725 / MS90726 (mil-spec), and BACB30NW / BACB30LE (Boeing) standards. Forged from AMS 5731 / 5732 / 5737 bar, solution-treated and precipitation-aged to ASTM A453 grade 660 Class A for 130 ksi tensile, 95 ksi yield, retained preload to 700 °C. CRES classification confirms the alloy retains corrosion resistance against jet-engine combustion gas, salt-fog, and marine atmospheres. See parent A286 bolts, sister variants A286 hex bolts, NAS bolts, socket head cap screws, and the canonical chemical composition + mechanical properties + heat treatment.
About A286 CRES Bolts
TorqBolt manufactures CRES A286 bolts for the US-spec aerospace and defence supply chain. CRES (Corrosion-Resistant Steel) is the legacy US designation that distinguishes austenitic-stainless-steel and precipitation-hardening-stainless-steel fasteners from the carbon-steel alloy bolts (typically marked PHCS or LAS). A286 falls in the CRES category: it is non-magnetic, austenitic, age-hardenable, oxidation-resistant to 982 °C, and remains corrosion-resistant in jet-engine, salt-fog and marine atmospheres. Each CRES A286 bolt is forged from A286 bar, thread-rolled, solution-treated and precipitation-aged to ASTM A453 grade 660 Class A. Lot traceability runs from VIM-VAR melt to finished bolt; AS9102 first-article inspection on every drawing/revision per AS9100D AQMS.
A286 CRES Bolt Head Patterns & Aerospace Standards
TorqBolt produces CRES A286 bolts in every aerospace head pattern and dimensional standard:
- NAS 1351 / 1352 (Socket Head Cap) — Aerospace SHCS — internal hex drive, MIL-S-8879 thread tolerance, magnetic permeability < 1.005. The most common CRES A286 fastener.
- NAS 6203 / 6204 (Reduced-shank SHCS) — Lighter-weight aerospace SHCS — reduced-diameter shank for fatigue performance. Specified on engine accessory and structural attachment bolts.
- NAS 6603-6620 (12-point bi-hex) — Bi-hex external drive for high-torque jet-engine compressor and turbine bolting. Lower head profile than hex for weight reduction.
- MS 90725 / 90726 (Hex bolt) — MIL-spec equivalent of ISO 4014 hex bolt — used on US military aerospace structure where MS-spec is invoked over commercial DIN/ISO.
- BACB30NW / BACB30LE (Boeing) — Boeing internal-spec CRES bolt patterns — manufactured to MIL-S-8879 thread tolerance with traceability per BAC 5004.
- AS3239 / IFI-115 (12-point flange) — Aerospace 12-point flange bolt — high-torque transmission with reduced under-head height for tight-clearance applications.
A286 CRES Bolt Sizes & Aerospace Spec Reference
| Size | Pitch | Standard | Drive | Min. tensile (lbf) | Marking |
|---|---|---|---|---|---|
| #10 (5 mm) | 32 UNF | NAS 1351N3 | Hex socket | 1,800 | A286 + lot |
| 1/4 (6 mm) | 28 UNF | NAS 1351N4 | Hex socket | 3,200 | A286 + lot |
| 5/16 (8 mm) | 24 UNF | NAS 1351N5 | Hex socket | 5,300 | A286 + lot |
| 3/8 (10 mm) | 24 UNF | NAS 1351N6 | Hex socket | 8,000 | A286 + lot |
| 7/16 (11 mm) | 20 UNF | NAS 1351N7 | Hex socket | 11,000 | A286 + lot |
| 1/2 (13 mm) | 20 UNF | NAS 1351N8 | Hex socket | 14,500 | A286 + lot |
| 5/8 (16 mm) | 18 UNF | NAS 6610 | 12-point | 23,500 | A286 + lot |
| 3/4 (19 mm) | 16 UNF | NAS 6612 | 12-point | 34,000 | A286 + lot |
A286 CRES Bolts Manufacturing Process
Every a286 cres bolts 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: AMS 5731 / 5732 chemistry from approved aerospace mills (ATI, Carpenter, Special Metals). All ingot heats traceable per AS9100D AQMS.
- Aerospace bar prep: Bar drawn or rolled to NAS 1351 / 6603 starting blank diameter. Surface inspected for laps, seams, and cracks per ASTM E45 inclusion rating.
- Cold heading (≤ M16): Multi-station cold-heading press: head trim, cone form, pilot, hex socket forming for SHCS or 12-point milling for NAS 6603. Aerospace lots use vacuum-degassed bar.
- Aerospace machining (M20+): 5-axis CNC machined for NAS 6603 12-point geometry — bi-hex drive cannot be cold-headed at large sizes.
- Thread rolling MIL-S-8879: Threads rolled to MIL-S-8879 Class 3 tolerance (tighter than commercial Class 2A). Roll-formed threads provide 30-40 % higher fatigue strength.
- Solution treatment: Vacuum heat-treat 1650 °F (899 °C, AMS 5737 / Cl. A) — aerospace standard. Vacuum environment prevents IGA / oxide contamination.
- Precipitation aging: 1325 °F (718 °C) for 16 hours, air-cool. Develops gamma-prime Ni₃(Ti,Al). Hardness 277-302 HBW (29-32 HRC).
- Passivation per ASTM A967: Pickle in HNO₃ / HF, water rinse, passivate per ASTM A967 Type II. Confirms removal of free iron and residual oxide.
- AS9102 first-article + lot serialization: First article on every new drawing or revision; lot serialized 1-N for full traceability per BAC 5004 / NAS 100. Head-stamped 'A286' + lot + 'TB'.
A286 CRES Bolts Inspection & Certification
Each lot ships with a signed inspection certificate. AS9100D-compliant aerospace lots include AS9102 first-article reporting on every new drawing or revision. Industrial orders default to EN 10204 type 3.1; sour-service and offshore step up to type 3.2 with third-party witness.
- 100 % thread-gauge GO/NO-GO per MIL-S-8879 Class 3 (tighter than commercial 2A).
- Hardness traverse 4-point Vickers per heat-treat batch per ASTM E384.
- Magnetic permeability < 1.005 per ASTM A342 — verified on every aerospace coil.
- LPI per ASTM E1417 Class 1 sensitivity on every aerospace lot.
- Tensile coupon from each heat — yield, tensile, elongation, RA per ASTM E8.
- AS9102 first-article inspection on first part of every new drawing/revision per AS9100D.
- Salt-spray ASTM B117 96-hour pass per ASTM A967 acceptance criterion.
- Lot serialization 1-N for traceability per BAC 5004 / NAS 100 (Boeing / Spirit).
A286 CRES Bolts Torque & Assembly Practice
CRES A286 bolts torque to 75 % of room-temperature 0.2 % yield (~71 ksi residual stress on grade 660 Class A) for static aerospace joints; 60 % of yield for cycling joints. Aerospace torque values from MIL-HDBK-60 or specific airframe assembly manual; never use commercial DIN / SAE J429 tables on CRES aerospace bolts. Above 540 °C apply nickel anti-seize per AS5272 to avoid austenitic-stainless thread galling. Aerospace OEMs (Boeing, Airbus, GE, P&W) typically mandate replacement of CRES bolts after one assembly cycle for primary-structure joints — re-use only on secondary structure with documented torque history.
A286 CRES Bolt Applications by Industry
CRES A286 bolts are the workhorse of US-spec aerospace and defence assemblies. Major applications:
- Jet-engine compressor & turbine: NAS 6603-6620 12-point CRES bolts hold compressor disc-to-disc and turbine wheel-to-shaft. The recurring choice for A286 jet engine fasteners.
- Aerospace structure: BACB30NW and BACB30LE CRES bolts on Boeing fuselage frame attach, wing-spar internal bolting, engine-mount lugs.
- Industrial gas turbines: CRES A286 NAS 1351 SHCS on combustor liner attachment, exhaust diffuser bolting, transition-piece retention. A286 gas turbine applications.
- Defence airframe: MS90725 / MS90726 CRES bolts on F-15, F-16, F-18 and F-35 structural and engine attach drawings.
- Space launch: CRES A286 bolts qualified for SpaceX, Blue Origin, Rocket Lab and ULA upper-stage and engine assemblies — non-magnetic + cryogenic + 700 °C ceiling.
- Naval / marine: CRES A286 bolts on naval gas-turbine LM2500 and LM6000 hot-section bolting, where salt-fog corrosion + high-temperature combine.
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 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 CRES Bolts 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 CRES Bolts
A complete a286 cres bolts callout should include: material spec, heat-treatment condition, dimensional standard, size, thread tolerance class, surface finish, marking, inspection certificate. Example callout:
NAS 1351-N6, A286 (UNS S66286), ASTM A453 grade 660 Class A, ST+A, 3/8 inch × 16 UNF, 3 inch length, MIL-S-8879 thread, magnetic permeability < 1.005, passivated, head-marked ‘A286’ + lot + ‘TB’, AS9102 first-article on lot, EN 10204 3.1 with NIST-traceable mill cert.
A286 CRES Bolts — Frequently Asked Questions
What does CRES mean on an A286 bolt?
CRES stands for Corrosion-Resistant Steel — the legacy US aerospace term for stainless and precipitation-hardening-stainless fasteners including A286, 17-4 PH, 17-7 PH, AM-355, and 13-8 Mo. CRES designation appears on US-spec aerospace drawings (NAS, MS, MIL, BAC) to distinguish from carbon-steel PHCS or LAS bolts.
Are CRES A286 bolts the same as commercial A286 bolts?
Material is identical (UNS S66286, ASTM A453 grade 660). Manufacturing differs: CRES bolts are produced under AS9100D AQMS with MIL-S-8879 Class 3 thread tolerance, AS9102 first-article inspection, and lot serialization. Commercial A286 bolts use ISO 4762 / DIN 912 commercial thread Class 2A and EN 10204 3.1 mill cert only.
What is the marking on a CRES A286 bolt?
Head-stamped 'A286' + lot number + manufacturer code 'TB'. Aerospace standards may add grade 'GR 660' for ASTM A453 traceability. NAS bolts add the NAS part number (NAS 1351N6) on the head. Stamp depth 0.05-0.10 mm raised or recessed per drawing.
What aerospace standards cover CRES A286 bolts?
NAS 1351 / 1352 / 6203 (socket head), NAS 6603-6620 (12-point), MS 90725 / 90726 (hex), BACB30NW / BACB30LE (Boeing), AS3239 / IFI-115 (12-point flange), MIL-S-8879 (thread tolerance), MIL-W-19140 (washers). Each cites A286 / UNS S66286 material per AMS 5732.
Are CRES A286 bolts magnetic?
No. A286 austenitic FCC matrix has magnetic permeability < 1.005, verified per ASTM A342 on every aerospace lot. This is preserved through manufacture, aging, and cold work — making CRES A286 the standard for instrumentation, MRI, magnetometer, and electromagnetic-sensitive aerospace assemblies.
Can CRES A286 bolts replace Inconel 718 bolts?
For service ≤ 700 °C — yes. CRES A286 is one-third the cost and meets the same temperature ceiling. For room-temperature applications requiring tensile > 1240 MPa, Inconel 718 is required. See A286 vs Inconel 718.
What thread tolerance applies to CRES A286 bolts?
MIL-S-8879 / ASME B1.13M Class 3A (inch) or 4g6g (metric) — tighter than commercial 2A / 6g. This is required for aerospace fatigue performance per NAS 6203 / NAS 1351 acceptance criteria.
Do CRES A286 bolts need passivation?
Yes. Passivated per ASTM A967 Type II (HNO₃ + HF) post-aging to remove free iron and residual oxide. Aerospace acceptance: 96-hour salt-spray pass per ASTM B117. Passivation does not affect magnetic permeability or mechanical strength.
Can CRES A286 bolts be re-used after disassembly?
Aerospace primary structure (engine mount, wing spar, fuselage frame): NO — single-use only. Secondary structure with documented torque history: yes, with thread-distortion and head-stamp inspection. Industrial / commercial applications: yes, multiple cycles permitted.
Why TorqBolt for A286 CRES Bolts
Three reasons aerospace and gas-turbine OEMs place a286 cres bolts orders with us:
- Vertically integrated supply — VIM-VAR melt sourcing from approved AMS-conforming mills, in-house cold heading + thread rolling + vacuum heat-treatment.
- Aerospace AQMS — AS9100D-certified factory in Mumbai with published quality manual covering A286 fastener-specific failure-mode analysis.
- Lead time discipline — 4-6 weeks for ASTM A453 grade 660 standard sizes, 8-12 weeks for custom-drawing aerospace parts.
Over thirty years in fastener manufacture with current ISO 9001:2015, AS9100D, PED, and NORSOK M-650 quality system audits.
Recent A286 CRES Bolts Order Patterns
Active CRES A286 bolt orders span jet-engine compressor disc retention (NAS 6610-6620 12-point), aerospace accessory gearbox SHCS (NAS 1351), military airframe bolting (MS 90725 / MS 90726), and helicopter rotor-head transmission bolts (BACB30NW). All shipped with AS9102 first-article inspection and AS9100D AQMS lot serialization.
Satisfaction Survey
