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Product Details
Copper Washers and Copper Plain Washers
Copper Washers and Copper Plain Washers
Copper washers are precision-blanked flat copper rings used under bolt heads and nuts in electrical busbar connections, grounding assemblies, switchgear hardware, plumbing fittings, and mechanical joints. Also known as copper plain washers, copper flat washers, copper fender washers, copper DIN 125 washers, copper finishing washers, copper contact washers, copper earthing washers, and copper penny washers, these components are manufactured from Cu-ETP (C11000) and Cu-DHP (C12200) copper strip by Electrical Accessories India. Supplied in all standard metric and imperial sizes to electrical OEMs, panel builders, EPC contractors, and distributors across 30+ countries.
Product Overview
Copper Plain Washers for Electrical Applications
Copper plain washers, copper DIN 125A washers, copper ISO 7089 washers, copper flat washers, and copper contact washers are used under bolt heads and nuts in busbar assemblies to distribute clamping load, prevent galling of soft copper busbars, maintain electrical continuity between bolt and busbar, and prevent bimetallic corrosion where stainless steel or zinc-plated steel bolts are used. Standard inner diameters: M4, M5, M6, M8, M10, M12, M16, M20. Outer diameters per DIN 125A, DIN 9021, ISO 7089, and ISO 7093. Material Cu-ETP for highest conductivity; Cu-DHP for plumbing applications.
Copper Busbar Washers and Earthing Washers
Copper busbar washers, copper earthing washers, copper bonding washers, copper grounding washers, and copper equipotential washers are used at bolted joints in busbar systems and grounding installations. They ensure electrical continuity is maintained across the joint interface, reduce the risk of paint or coating insulating the joint, and provide a conductive contact face regardless of surface preparation. Toothed (serrated) variants bite through surface oxide layers on first assembly. Available in plain, external-tooth, internal-tooth, and split-ring forms from Cu-ETP copper.
Copper Fender Washers and Large-OD Washers
Copper fender washers, copper mudguard washers, copper large-diameter washers, and copper penny washers have an oversized outer diameter relative to the bolt hole, providing a large bearing surface on soft materials such as plastic enclosures, rubber grommets, and wood. These are blanked from Cu-ETP sheet in thicknesses from 0.5 to 3.0 mm. Custom OD/ID ratios are available. Applications include panel fixings, cable entry sealing plates, grounding plates on enclosure walls, and decorative architectural applications requiring copper finish.
Copper Spring and Disc Spring Washers
Copper spring washers (split ring), copper Belleville washers (disc springs), copper wave washers, and copper conical washers are formed copper components that maintain bolt tension under vibration and thermal cycling. Used in electrical panel hardware subject to vibration (generator sets, motor-mounted panels, rail vehicles), these washers prevent bolt loosening and maintain joint clamping force. Spring washers are formed from half-hard Cu-ETP; Belleville washers require harder copper alloy or phosphor bronze depending on spring force requirement. Custom spring rates and load specifications on request.
Copper Reducing Washers and Speedo Washers
Copper reducing washers, copper conduit reducing washers, copper concentric reducing washers, and copper eccentric reducing washers are used to adapt larger cable gland or conduit knockout entries to smaller cable gland sizes. Blanked from Cu-ETP sheet, these are used in metal enclosures and switchgear where the knockout diameter is larger than the cable gland metric thread. Standard DIN and BS reducing washer dimensions. Custom profiles for non-standard conduit knockouts are blanked to drawing.
Key Features
- Cu-ETP (≥100% IACS) and Cu-DHP copper grades — standard in-stock
- Standard metric sizes: M4 through M30 inner diameter
- DIN 125A, DIN 9021, ISO 7089, ISO 7093 dimensional standards
- Thickness range: 0.5 mm to 6.0 mm
- Plain, toothed (serrated), split, wave, and Belleville forms
- Tin-plated, bare copper, and nickel-plated finishes
- Custom OD/ID and thickness to drawing
- Full material test reports and REACH/RoHS compliance
Standard Dimensional Compliance
Copper plain washers are manufactured to DIN 125A (normal washer), DIN 125B (chamfered washer), DIN 9021 (large washer), ISO 7089 (plain washer normal), and ISO 7093 (plain washer large) dimensional standards. Inner diameter tolerance: +0.1/+0.3 mm for M4–M12; +0.2/+0.5 mm for M16–M30. Outer diameter tolerance: ±0.3 mm for M4–M12; ±0.5 mm for M16–M30. Thickness tolerance: ±0.1 mm for standard washers; ±0.05 mm for precision washers. Flatness within 0.2 mm per 25 mm diameter.
Electrical Conductivity and Joint Performance
Cu-ETP copper washers provide ≥100% IACS conductivity, ensuring that washer resistance is negligible in a bolted joint. At a bolted busbar joint, the total joint resistance is dominated by the contact interface resistance rather than the washer. Using copper washers ensures galvanic compatibility with copper busbars, avoiding copper-to-steel or copper-to-aluminium bimetallic contact. Tin-plated copper washers are specified where long-term interface resistance stability is required — tin plating prevents oxidation and maintains low contact resistance over the installation lifetime.
Corrosion Resistance and Surface Finish
Bare Cu-ETP copper washers are suitable for indoor, protected installations where immediate assembly is confirmed. For outdoor, coastal, and marine installations, tin-plated copper washers (5–15 μm electroplated tin) or hot-dip tinned washers are specified. Nickel plating (3–10 μm) is used for high-temperature applications up to 200°C. Bare copper washers will form a protective green patina (cupric carbonate) over time in outdoor environments, providing corrosion protection without loss of structural integrity.
Material Selection by Application
Cu-ETP (C11000) is standard for electrical applications — highest conductivity, lowest cost. Cu-DHP (C12200, CW024A) is preferred for plumbing and hydraulic applications where hydrogen atmosphere exposure or welding is involved — phosphorus deoxidization prevents embrittlement. Cu-OF (C10200) is used for vacuum brazing and hydrogen-atmosphere applications. Phosphor bronze (C51000, CuSn5) washers are available where spring properties or higher strength are needed. Custom alloy selection is available on request.
Size Range and Customisation
Standard inner diameters: M4 (4.5 mm) through M30 (33 mm). Outer diameters: per DIN/ISO standard or custom. Thickness: 0.5 mm to 6.0 mm standard; 0.1 mm to 10 mm on request. Custom OD/ID ratios for non-standard applications. Maximum blank size: 200 mm OD. Profile tolerances: ±0.1–0.3 mm depending on size. Custom profiles with tabs, sectors, and non-circular forms are blanked to drawing.
Technical Specifications
| Parameter | Specification |
|---|---|
| Base Material | Cu-ETP C11000, Cu-DHP C12200, Cu-OF C10200 |
| Purity | ≥99.90% copper |
| Conductivity | ≥100% IACS (Cu-ETP) |
| Thickness Range | 0.5 mm to 6.0 mm standard |
| Inner Diameter | M4 (4.5 mm) to M30 (33 mm) + custom |
| Outer Diameter | Per DIN 125A/ISO 7089 or custom |
| Dimensional Standard | DIN 125A, DIN 9021, ISO 7089, ISO 7093 |
| Surface Finish | Bare copper, Tin-plated (5–15 μm), Nickel-plated (3–10 μm) |
| Tensile Strength | 200–250 MPa (annealed Cu-ETP) |
Material Grades and International Equivalents
| India IS | USA ASTM/UNS | UK BS EN | Germany DIN | Europe EN | ISO | Common Name |
|---|---|---|---|---|---|---|
| IS 191 Grade 1 | C11000 / ASTM B187 | CW004A / BS EN 13601 | E-Cu57 / DIN 1787 | EN CW004A | ISO 1337 | Cu-ETP, Electrolytic Tough Pitch Copper |
| IS 191 Grade 3 | C12200 / ASTM B280 | CW024A / BS EN 1057 | SW-Cu / DIN 1787 | EN CW024A | ISO 1337 | Cu-DHP, Phosphorus Deoxidized Copper |
Product Types and Variants
Plain flat washers (DIN 125A, ISO 7089); large plain washers (DIN 9021, ISO 7093); toothed/serrated washers (external, internal, both); split ring spring washers; Belleville disc spring washers; wave washers; fender/mudguard washers; reducing/adaptor washers; custom OD/ID profiled washers; copper penny washers; copper contact washers (toothed).
Applications in Industry
Busbar bolt connections in LV/MV switchgear; earthing and bonding bolt connections; cable lug-to-busbar interfaces; conduit and cable gland reducing adapters; plumbing fittings (Cu-DHP); hydraulic connections; panel fixing hardware; transformer terminal connections; cable tray grounding; generator terminal connections; solar PV mounting rail earth connections.
Manufacturing Process
- Copper strip procurement — Cu-ETP/Cu-DHP ASTM B187/B280 with MTC
- Incoming inspection — composition (XRF), thickness, hardness, conductivity
- Blanking and punching — progressive die or single-hit; outer and inner diameter simultaneously
- Deburring — barrel deburring; burr <0.05 mm
- Toothing (if applicable) — external or internal tooth forming
- Cleaning — alkaline degreasing, acid pickling, rinse
- Plating — barrel electroplating (tin, nickel)
- Dimensional inspection — 100% visual; sampling OD, ID, thickness measurement
- Packing — bulk box or poly-bagged packs; export carton with documentation
Quality Standards and Certifications
Material: ASTM B187, BS EN 13601. Dimensions: DIN 125A, DIN 9021, ISO 7089, ISO 7093. Plating: IEC 60068-2-20 (tin). ISO 9001:2015 QMS. REACH and RoHS compliance. EN 10204 Type 3.1 material test certificates on request.
Why Choose Electrical Accessories India
Electrical Accessories India manufactures copper washers from 0.5 mm to 6.0 mm thickness in all standard metric sizes at its Jamnagar facility. In-house blanking tools cover the full range of DIN and ISO washer standards. We maintain copper strip inventory for immediate production. Custom OD/ID ratios, non-standard sizes, and special finishes are available. Full material documentation, REACH, and RoHS compliance certificates are standard. We export to 30+ countries.
Frequently Asked Questions (FAQ)
What is the difference between DIN 125A and DIN 9021 copper washers?
DIN 125A is the standard washer with normal OD (approximately 2× the bolt diameter). DIN 9021 is the large (wide) washer with OD approximately 3× the bolt diameter, providing greater load distribution on soft materials or where large bearing areas are needed.
What copper grade should be used for plumbing washers?
Cu-DHP (C12200, CW024A) is the recommended grade for plumbing and hydraulic applications. It is phosphorus-deoxidized, suitable for welding and brazing, and resistant to hydrogen embrittlement. Cu-ETP is not recommended for welded or hydrogen-atmosphere applications.
Are copper washers available with tin plating?
Yes. Electrolytic tin plating (5–15 μm) is available as a standard option. Tin-plated copper washers are recommended for long-term outdoor and coastal installations to prevent oxidation and maintain electrical contact resistance.
What is the minimum order quantity?
Standard DIN/ISO sizes: 200 pieces minimum. Custom sizes: 500 pieces. Small samples of 25–50 pieces available for qualification.
Can copper washers be supplied with an outside tooth for grounding?
Yes. External-tooth serrated copper washers (toothed lock washers) are available. The teeth bite through surface oxide films and coatings to ensure a reliable electrical grounding contact.
Are copper washers RoHS and REACH compliant?
Yes. Cu-ETP and Cu-DHP copper are inherently RoHS and REACH compliant. Tin plating is also compliant. Compliance certificates are included with each shipment.
What is the maximum size of copper washer you can manufacture?
Standard blanking: up to 200 mm OD. Larger diameter washers (copper rings) up to 500 mm OD are available by waterjet or laser cutting from copper plate.
Do you supply reducing washers for cable glands?
Yes. Copper reducing washers for conduit knockouts are manufactured in standard DIN and BS dimensions and custom sizes to accommodate non-standard enclosure knockout diameters.
Equivalent Terms – Multilingual Reference
| Language | Term 1 | Term 2 | Term 3 |
|---|---|---|---|
| Spanish | Arandela de cobre | Arandela plana de cobre | Arandela de cobre lisa |
| Russian | Медная шайба | Медная плоская шайба | Шайба из меди |
| French | Rondelle en cuivre | Rondelle plate en cuivre | Rondelle cuivre DIN |
| Portuguese | Arruela de cobre | Arruela plana de cobre | Arruela lisa de cobre |
| Italian | Rondella in rame | Rondella piatta in rame | Rosetta in rame |
Related Products and Linked Terms
- Copper Pressing and Copper Pressed Parts
- Copper Busbar Links – Flexible Busbar Connectors
- Copper Grounding Terminals – Earth Terminals
- Copper Earthing Tags – Earth Tags and Grounding Labels
- Copper Switch Contacts – Electrical Contact Tips
- Copper Fuse Clips – Pressed Copper Fuse Clips
- Copper Shims and Copper Shim Washers
- Copper Washers and Copper Plain Washers
- Copper Sealing Washers – Crush Washers
- Copper Pipe Brackets and Copper Pipe Clamps
- Copper Deep Drawn Sheet Metal Parts
- Copper Machined Parts
Indicative Pricing
Copper Items: US$ 15.80 per kilogram, CIF USA Port
Prices are indicative and subject to change based on quantity, specification, alloy grade, and market conditions. Contact us with your RFQ for a firm quotation.
Request a Quote
Supply your drawing or specification and receive a detailed technical and commercial proposal within 24 hours. Electrical Accessories India engineers are available to advise on washer standard, material, size, and finish.
Contact us: Send your RFQ with quantity, inner diameter, outer diameter, thickness, material, and surface finish requirements. We respond within 24 business hours.