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 Flat Washers
A286 flat washers distribute the bearing load from A286 hex bolts and A286 hex nuts across a wider footprint, prevent scoring of mating surfaces, and provide an axial spacer / shim function. TorqBolt manufactures A286 flat washers to DIN 125 (standard), DIN 9021 (oversize / fender), ISO 7089 (Form A standard) and ISO 7093 (Form B large), plus aerospace AN-960, NAS-620 and MS-15795 standards. Stamped or laser-cut from A286 sheet (AMS 5895) or plate (AMS 5525), then solution-treated and aged to ASTM A453 grade 660. The non-magnetic austenitic matrix and high-temperature retention to 700 °C make A286 flat washers the natural mate to A286 fasteners. See parent A286 washers overview, sister lock washers, and the canonical A286 chemical composition + mechanical properties pages.
About A286 Flat Washers
A286 flat washers are produced in three primary forms: Form A standard (ISO 7089 / DIN 125), Form B large / fender (ISO 7093 / DIN 9021), and Aerospace AN-960 / NAS-620 (per MIL-W-19140). Each washer is blanked from solution-treated A286 sheet, deburred, and aged at 1325 °F for 16 hours per AMS 5895 / 5525 condition. Thickness ranges from 0.4 mm (M3) to 4 mm (M64). Outer diameter follows the corresponding standard — 200 % bolt nominal for DIN 125, 300 % for DIN 9021. The non-magnetic, oxidation-resistant, age-hardenable austenitic matrix retains compressive stiffness to 700 °C, so A286 flat washers do not relax the bolt preload at gas-turbine, jet-engine and exhaust-system operating temperatures.
A286 Flat Washer Types & Dimensional Standards
Five canonical A286 flat washer forms:
- Form A standard (ISO 7089 / DIN 125) — Outer ⌀ ≈ 2× bolt nominal. Default flat washer for general A286 bolted-joint pairing. M3 to M64.
- Form B large / fender (ISO 7093 / DIN 9021) — Outer ⌀ ≈ 3× nominal. Spreads load over softer mating material (cast iron, aluminium, fibre composite) — used under M5-M30 fasteners on aerospace tank-flange and pressure-vessel hardware.
- Aerospace AN-960 / NAS-620 / MS-15795 — Inch series #4 to 2". AMS 5525 sheet substrate, AS9102 first-article inspection. Used on US-spec aerospace structural and engine assemblies.
- Oversize / square / spherical washer — Custom-drawing parts: square (DIN 436) for timber-to-metal connections, spherical-faced (DIN 6319) for self-aligning with offset bolts, conical-faced for V-flange joints.
- PTFE / electrical-insulating washer (composite, not pure A286) — Note: where electrical insulation is required between the bolt and the joint, a separate PTFE or phenolic insulating washer is needed in addition to the A286 flat washer — A286 itself is electrically conductive.
A286 Flat Washer Sizes & Dimensions
| For bolt size | Form A inner ⌀ | Form A outer ⌀ | Thickness | Form B outer ⌀ | Form B thickness |
|---|---|---|---|---|---|
| M3 | 3.2 mm | 7 mm | 0.5 mm | 9 mm | 0.8 mm |
| M4 | 4.3 mm | 9 mm | 0.8 mm | 12 mm | 1.0 mm |
| M5 | 5.3 mm | 10 mm | 1.0 mm | 15 mm | 1.2 mm |
| M6 | 6.4 mm | 12 mm | 1.6 mm | 18 mm | 1.6 mm |
| M8 | 8.4 mm | 16 mm | 1.6 mm | 24 mm | 2.0 mm |
| M10 | 10.5 mm | 20 mm | 2.0 mm | 30 mm | 2.5 mm |
| M12 | 13 mm | 24 mm | 2.5 mm | 37 mm | 3.0 mm |
| M16 | 17 mm | 30 mm | 3.0 mm | 50 mm | 3.0 mm |
| M20 | 21 mm | 37 mm | 3.0 mm | 60 mm | 4.0 mm |
| M24 | 25 mm | 44 mm | 4.0 mm | 72 mm | 4.0 mm |
A286 Flat Washers Manufacturing Process
Every a286 flat washers 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:
- A286 sheet input: A286 sheet (AMS 5895 aged) or plate (AMS 5525 sol-treated) sourced VIM-VAR with surface finish No. 2D (matte) or No. 4 (brushed). Thickness selected from washer-thickness table per DIN / ISO.
- Blanking / stamping (sizes ≤ M30): High-tonnage punch press blanks washers from sheet — circular punch + die set with 5 % clearance. Single-stroke for thicknesses ≤ 2 mm, double-stroke for 2-4 mm to control burr.
- Laser / waterjet cutting (sizes > M30): Larger washers and oversize fender forms cut by fibre laser or abrasive waterjet from plate — preserves heat-affected zone < 0.2 mm and avoids stamping-induced cold work.
- Tumbling / deburring: All washers vibratory-tumbled with ceramic media to break edges and remove blanking burr. Aerospace lots add hand-deburr inspection per AS5272 surface condition.
- Solution treatment (if required): Sheet typically supplied solution-treated (AMS 5895 condition). If full age-hardening is required, post-blanking solution + age cycle: 1650 °F sol → oil quench → 1325 °F aging × 16 h.
- Precipitation aging: Aerospace washers age-hardened post-blanking to develop full strength matching A286 fastener mating. Standard washers may ship sol-treated only — aging optional per drawing.
- Passivation: Dipped in HNO₃ + HF pickle, water-rinsed, passivated per ASTM A967 type II. Optional silver or nickel anti-galling coat on bearing face for above-540 °C service.
- Inspection: Thickness gauge (calliper or micrometer) on every washer; OD/ID dimensional check by ring gauge; flatness check on stack of 10 (max deviation 0.05 mm); 100 % visual for burr / crack.
- Marking & packing: Lot-marked container (washers themselves not marked due to surface area). Heat traceability label, vacuum-bagged for corrosion protection. 1000-piece bulk pack standard.
A286 Flat Washers 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:
- Thickness 100 % gauged with calibrated calliper or micrometer — tolerance ±0.10 mm per DIN 125, ±0.15 mm per AN-960.
- OD / ID dimensional check by ring gauge — typical tolerance ±0.30 mm at M16 OD.
- Flatness check by stacking 10 washers — total stack deviation max 0.05 mm × N pieces.
- 100 % visual inspection for blanking burr (≤ 0.05 mm per AN-960), surface scratch, and edge crack.
- Hardness on heat-treat-aged lots — Vickers HV per ASTM E384, sampling 1 per 500 washers.
- Magnetic permeability < 1.005 per ASTM A342 on every aerospace lot.
- Surface finish per ASTM A480 — No. 2D matte or No. 4 brushed depending on application.
- Salt-spray ASTM B117 for passivated lots — 96-hour pass per A967 acceptance criterion.
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 Flat Washers Torque & Assembly Practice
Flat washers do not transmit torque — they distribute the bolt-head or nut bearing pressure across a wider footprint. Selection of flat washer determines the bolt-head clamping pressure on the joint substrate. Use Form A standard (DIN 125) when the substrate is steel of the same hardness as the fastener; switch to Form B oversize (DIN 9021) when the substrate is softer (aluminium, cast iron, fibre composite) and the larger bearing area prevents joint embedment. For temperatures above 540 °C, the washer bearing surface gall-loads against the nut face — apply silver or nickel anti-galling coat to the washer top surface. Stack-up of two flat washers under a single nut is acceptable; three or more cause spring-rate compression and unreliable preload.
A286 Flat Washer Applications by Industry
Flat washers complete the A286 fastener stack. Industrial applications:
- Aerospace engine assemblies: AN-960 and NAS-620 flat washers under jet-engine compressor and turbine fasteners — distributes preload across thin-wall casing flanges. A286 jet engine fasteners.
- Industrial gas turbines: DIN 125 standard washers on casing-split bolting; DIN 9021 oversize on combustor liner attachment to ceramic-coated panels. A286 gas turbine applications.
- Turbocharger / exhaust: DIN 9021 oversize washers under hex flange nuts on cast-iron exhaust manifolds — protects manifold face from nut bearing damage at 700 °C.
- Cryogenic LNG / hydrogen: A286 flat washers under valve-bonnet and pump-flange bolting at -196 °C. Retains 85 % of RT compressive stiffness.
- Nuclear pressure vessel: ASME III heavy flat washers on pressuriser, steam-generator and reactor-vessel bolting per A453 grade 660.
- Instrumentation / non-magnetic: Custom thin AN-960L or DIN 988 shim washers for MRI, particle-accelerator, magnetometer assemblies. Permeability < 1.005.
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 Flat Washers 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). A286 wins the 540-700 °C cost-per-MPa-of-retained-preload comparison cleanly. See the consolidated A286 equivalent grades reference for full alloy alternatives.
How to Specify A286 Flat Washers
A complete a286 flat washers 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:
Flat washer, ASTM A453 grade 660, AMS 5895 sheet, ST+A, DIN 125 Form A, ID 17.0, OD 30.0, thickness 3.0 mm, passivated, EN 10204 3.1.
A286 Flat Washers — Frequently Asked Questions
What is the difference between DIN 125 and DIN 9021 A286 flat washers?
DIN 125 (Form A) outer ⌀ ≈ 2× bolt nominal — the default flat washer. DIN 9021 (Form B / fender / oversize) outer ⌀ ≈ 3× nominal — spreads load over softer mating material like aluminium, cast iron or composite. Use DIN 9021 when the mating face is at risk of scoring or deformation under bolt preload.
Can A286 flat washers be re-used?
Generally yes for non-critical industrial joints, provided no thickness change > 5 % and no visible scoring on the bearing face. Aerospace and nuclear practice mandates one-time use — replace washer with each fastener replacement.
Are A286 flat washers electrically conductive?
Yes. A286 is metallic and conductive. If electrical isolation between two metal components is required (lightning bonding, anode-isolation), use a phenolic, PTFE or fibreglass insulating washer in addition to or in place of the A286 flat washer.
What thickness A286 flat washer for an M16 hex bolt?
DIN 125 standard form: 3.0 mm thickness, 30 mm outer ⌀, 17 mm inner ⌀. DIN 9021 oversize form: 3.0 mm thickness, 50 mm outer ⌀, 17 mm inner ⌀. Both per ASTM A453 grade 660 / AMS 5895 sheet substrate, solution-treated and aged.
What is AN-960 vs NAS-620 vs MS-15795 A286 flat washer?
All three are inch-series aerospace flat washer standards. AN-960 is Air Force / Navy general-purpose. NAS-620 is National Aerospace Standard, slightly tighter dimensional tolerance. MS-15795 is the current MIL Standard supersession of AN-960 — functionally equivalent. TorqBolt manufactures all three from the same A286 / AMS 5895 substrate.
Can A286 flat washers be used at -196 °C cryogenic temperature?
Yes — A286 retains 85 % of room-temperature compressive stiffness at -196 °C (liquid nitrogen). Used on LNG valve-bonnet flange bolting, cryogenic pump bolting, and hydrogen storage vessel internals. Confirm the entire fastener stack (bolt + nut + washer) is A286 for matched thermal expansion.
What is the flatness tolerance on an A286 flat washer?
Per DIN 125 / ISO 7089: max deviation 0.05 mm × N pieces stacked. So 10 washers stacked must measure within 0.5 mm of nominal total thickness. Aerospace AN-960 / NAS-620 has tighter ±0.05 mm individual tolerance.
Are A286 flat washers age-hardened?
Optional. AMS 5895 sheet substrate ships solution-treated; washer is post-aged 1325 °F × 16 hours per drawing requirement. Aerospace flat washers are typically aged to develop full A286 strength for compressive stiffness retention at temperature. Industrial flat washers may ship sol-treated only.
What is the difference between a flat washer and a lock washer?
Flat washer = simple flat ring, distributes bearing pressure. Lock washer = split-ring (Belleville) or toothed-edge (external/internal star) — provides anti-vibration locking. See A286 lock washers for the locking variants. For high-temperature service > 540 °C, lock washers lose their spring-back and become equivalent to flat washers — use jam-nut or self-locking nut instead.
Why TorqBolt for A286 Flat Washers
Three reasons aerospace and gas-turbine OEMs place a286 flat washers 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 Flat Washers Order Patterns
Active flat-washer orders span aerospace engine assembly (AN-960 #4 to 1/2 inch), gas-turbine combustor casing oversize (DIN 9021 M16 / M20), MRI peripheral hardware (non-magnetic 6 mm thin), and petrochemical heat-exchanger flange (Form B oversize M24).
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