ASME / ASTM Standards
- ASME B18.22.1 (Type A & B)
- ASTM F436 / F436M (Structural)
- ASTM F844 (Un-hardened Steel)
- ASME B18.21.1 (Helical/Spring)
- ASTM A193 / A194 Matching Systems
ISO 9001:2015Certified quality management
PED 2014/68/EUApproved by TUV Rheinland
EN 10204 3.1 / 3.2Full heat-number traceability
Global DeliveryExporting to over 60 countries
Metric RangeM3 – M100
Imperial Range#4 – 4" Diameter
Tolerancesh13 / H13 per ISO 286-2
Sour ServiceNACE MR0175 Compliant
Engineering & Manufacturing Overview
Precision Engineered Industrial Flat Washers
Flat washers are indispensable components in high-pressure bolted joints, heat exchangers, subsea equipment, and critical structural connections. Engineered to distribute tightening preload evenly over a larger bearing surface, they protect flange faces from galling, bridge oversized or slotted clearance holes, and maintain joint stiffness under extreme thermal and mechanical loads.
At TorqBolt Inc., we manufacture standard and custom flat washers using precision stamping, fine blanking, laser cutting, and CNC machining. Every washer is produced to stringent geometrical tolerances with verified flatness and parallelism, ensuring uniform load distribution without localized stress concentrations.
Load Distribution
Spreads tightening forces uniformly to prevent surface crushing and maintain preload across wide operating temperature envelopes.
Galling Prevention
Hardness-balanced design prevents contact surface brinelling and galling against softer flange faces and mating components.
Total Traceability
Heat-number stamped and accompanied by comprehensive EN 10204 3.1 or 3.2 inspection certifications.
Core Standard Configurations
Washers are manufactured in compliance with international dimensional standards to match bolts and nuts in petrochemical, offshore, and nuclear service:
- Form A (Standard Plain): DIN 125-A / ISO 7089 — standard outside diameter for general industrial bolting assemblies.
- Form B (Large OD / Fender): DIN 9021 / ISO 7093 — expanded bearing area specifically designed for softer mating alloys and thin-sheet assemblies.
- Form C / Structural (Thick Section): DIN 7349 / ISO 7094 / ASTM F436 — heavy-gauge washers engineered for high-strength bolting and slotted holes.
- Custom Formats: Square plate washers (DIN 436), tab/lock-tang washers (DIN 462/463), and spherical seating washers for misaligned flanges.
Technical Parameters
Flat Washer Dimensional & Metallurgical Specifications
TorqBolt controls hardness, surface finish, and edge break profiles according to project requirements and international bolting standards.
| Parameter | Standard / Range | Engineering Specification Notes |
|---|---|---|
| Dimensional Standards | ASME B18.22.1, ASTM F436, DIN 125, DIN 9021, ISO 7089, ISO 7093, BS 4320 | Manufactured in both Narrow, Regular, and Wide series |
| Diameter Range | Metric: M3 to M100 | Imperial: #4 to 4.00" | Custom thicknesses up to 25 mm produced via CNC turning |
| Dimensional Tolerances | ISO 286-2 (OD: h13 | ID: H13) | Precision flatness ≤ 0.05 mm per 100 mm; deburred edges standard |
| Hardness Control | Plain: 140–200 HV | Hardened (ASTM F436): 38–45 HRC | Controlled through vacuum heat treatment, solution annealing, or age hardening |
| Surface Finish | Ra 1.6 µm standard (Ra 0.8 µm for high-integrity seal rings) | Clean, bright, passivated finish free from stamping burrs and cracks |
| Quality Certification | EN 10204 3.1 MTR standard; EN 10204 3.2 available | Traceable melt heat number with chemical, mechanical, and hardness validation |
Dimensional Standards
International Bolting & Washer Specifications Supported
TorqBolt produces washers directly complementary to global fastener standards, ensuring complete mating compatibility across assemblies.
DIN Standards
- DIN 125 (Forms A & B)
- DIN 9021 (Large Outer Diameter)
- DIN 433 (Small Outer Diameter)
- DIN 7349 (Heavy for Screws)
- DIN 436 (Square Structural Washers)
ISO Standards
- ISO 7089 (Normal series, Form A)
- ISO 7090 (Normal series with chamfer)
- ISO 7091 (Normal series, product grade C)
- ISO 7093 (Large series, Form B)
- ISO 7094 (Extra large series)
BS & UNI Standards
- BS 4320 (Sizes M1.6 – M68)
- BS 3410 (Imperial Plain Washers)
- UNI 6592 (Plain Washers)
- UNI 6593 (Large OD Washers)
- BS 4464 (Spring & Lock Washers)
Metallurgical Expertise
Available Alloys & Specialized Coatings
Our flat washers are fabricated from certified wrought bar, plate, and strip sourced from reputable mills, engineered to withstand sour wells, extreme cryogenic temperatures, and oxidizing chemicals.
Surface Treatments & Engineered Coatings
Electro Zinc Plating Hot Dip Galvanizing (ASTM A153) PTFE Fluorocarbon (Xylan) Aluminizing Ceramic Filled Fluorocarbon Electroless Nickel Plating Mechanical Zinc Plating Electro Zinc-Cobalt Electro Zinc-Nickel Phosphate & Oil Electro Cadmium Plating Dacromet 320 / 500 Pickled & Passivated Silver Plating
Material Grades & Specialty Alloys
AISI 304 / 304L / 304H AISI 316 / 316L / 316Ti AISI 317L / 321 / 347 AISI 904L (UNS N08904) 17-4 PH (UNS S17400) 15-5 PH (UNS S15500) A286 (UNS S66286) Duplex 2205 (UNS S32205 / S31803) Super Duplex 2507 (UNS S32750) Zeron 100 (UNS S32760) Inconel 600 / 601 Inconel 625 (UNS N06625) Inconel 718 (UNS N07718 / API 6A) Inconel X750 Incoloy 800 / 800H / 825 / 925 Hastelloy C276 / C22 / B2 Monel 400 / Monel K-500 Titanium Grade 2 / Grade 5 Cupronickel 70/30 & 90/10 Nitronic 50 / Nitronic 60 Waspaloy (UNS N07001) Aluminium 7075-T6 Silicon Bronze / Phosphor Bronze
Knowledge Center
Frequently Asked Questions About Flat Washers
What material grades are available for TorqBolt flat washers?
TorqBolt manufactures flat washers across austenitic stainless steels (304, 316L), duplex and super duplex steels (2205, 2507, Zeron 100), nickel superalloys (Inconel 625, Inconel 718, Hastelloy C276, Monel 400), Titanium alloys, and copper-nickel alloys. Certified mill test reports per EN 10204 3.1 or 3.2 accompany every delivery.
What dimensional standards and size ranges do you support?
We manufacture flat washers according to ASME B18.21.1, ASME B18.22.1, ASTM F436, DIN 125, DIN 9021, ISO 7089, and ISO 7093. Standard sizing spans metric M3 through M100 and imperial 1/8" up to 4" ID, with custom dimensions, thicknesses, and tolerances engineered to order.
Can flat washers be certified for sour-gas service (NACE MR0175 / ISO 15156)?
Yes. Fasteners and washers intended for sour oil and gas service can be fully certified to NACE MR0175 / ISO 15156 with verified microstructures, precise solution-annealed or aged heat treatments, and documented maximum hardness limits.
What quality inspections and third-party witness options are available?
TorqBolt provides Positive Material Identification (PMI), dimensional checks with optical profile projectors, surface roughness verification, hardness testing, and intergranular corrosion tests. Third-party witness inspections by Lloyd's Register, DNV, TUV, Bureau Veritas, or SGS are readily accommodated.