Copper Bolts, Copper Hex Set Screws

Copper Bolts and Copper Hex Set Screws

Electrical Accessories India manufactures precision copper bolts and copper hex set screws from high-conductivity copper alloys for critical electrical and power industry applications. These fasteners combine the mechanical holding strength of a bolted joint with the high electrical conductivity of copper, making them indispensable in busbar systems, transformer terminations, switchgear assemblies, earthing installations, and power distribution panels. With a conductivity of 98–101% IACS (International Annealed Copper Standard), copper fasteners are specified wherever standard steel or brass fasteners would introduce resistive losses or create galvanic incompatibility with copper conductors.

Product Overview

High-Conductivity Copper Bolts for Electrical Applications

Our copper bolts are precision-machined or cold-headed from ETP copper (C11000), oxygen-free copper (C10100), and phosphorus deoxidised copper (C12200). They are used extensively in busbars, cable lug connections, battery terminal assemblies, HV/LV transformer terminations, cable gland plates, motor terminal boxes, earth clamps, copper earthing conductors, and switchboard bus connections. The high conductivity ensures minimal contact resistance at bolted joints, which is critical for power quality in high-amperage circuits.

Copper Hex Set Screws – Full Thread and Partial Thread

Copper hex set screws (also known as hex head cap screws with full-thread or hex bolts with partial thread) are available in fully threaded and partially threaded configurations. Applications include transformer core clamping bolts, reactor mounting hardware, panel earth studs, cable tray earthing screws, grounding bus connectors, HV equipment mounting bolts, surge arrester hardware, and copper-to-copper joint fasteners. The hex head geometry allows torque application with standard tooling, ensuring repeatable clamp load without deforming soft copper thread inserts.

Threaded Forms and Dimensional Standards

All copper bolts and hex set screws are manufactured to DIN 933 (full thread), DIN 931 (partial thread), ISO 4017, ISO 4014, ASME B18.2.1, and IS 1363/1364 specifications. Thread forms available: ISO Metric Coarse (MC), ISO Metric Fine (MF), UNC (Unified National Coarse), UNF (Unified National Fine), and BSW (Whitworth). Dimensions conform to tolerance class 6g for external threads. Head-across-flat (AF) and head height dimensions comply with the respective DIN/ISO standards for interchangeability.

Material Grades and Alloy Composition

Three principal copper grades are stocked: C11000 (ETP – Electrolytic Tough Pitch copper, 99.9% Cu min., 100% IACS), C10100 (OFE – Oxygen-Free Electronic copper, 99.99% Cu min., 101% IACS), and C12200 (DHP – Phosphorus Deoxidised High Phosphorus copper, 99.9% Cu min., 85% IACS, superior weldability). C11000 is the standard grade for most electrical fastener applications; C10100 is specified for semiconductor, aerospace, and ultra-low oxygen environments; C12200 is preferred where post-fabrication brazing or welding of the fastener is required.

Surface Finish and Protective Treatments

Standard supply is bright bare copper. Optional surface treatments include: tin plating (EN/IEC 60068 compliant, 3–15 µm), nickel plating (5–25 µm electroless or electrolytic), silver plating (for high-frequency and low-contact-resistance applications), chrome passivation, and oxidation inhibitor coating. Tin-plated copper bolts are widely specified in tropical and coastal electrical installations to prevent oxidation-induced resistance increase at bolted joints. Silver-plated versions are used in high-temperature busbar joints above 105°C.

Size Range and Custom Manufacturing

Standard production range: M3 to M36 (metric) and 1/4″ to 1-1/2″ (inch series). Lengths from 6 mm to 300 mm (longer lengths by order). Custom thread pitches, non-standard AF dimensions, T-head bolts, eye bolts, J-bolts, foundation bolts, and special-purpose copper fasteners are manufactured to buyer drawings or samples. Minimum order: 10 kg per size/grade combination. Lead time: 2–4 weeks for standard; 4–6 weeks for custom.

Corrosion Resistance and Galvanic Compatibility

Copper has excellent atmospheric corrosion resistance and is galvanically compatible with copper conductors, tin-plated copper busbars, bronze connectors, and brass terminals. It is, however, galvanically dissimilar to aluminium and zinc, so insulating washers (nylon or PTFE) must be used in aluminium busbar assemblies with copper bolts. Copper fasteners exhibit excellent resistance to industrial atmospheres, seawater, steam, and most organic acids—making them suitable for chemical plants, coastal substations, offshore platforms, and marine electrical installations.

Key Features

• Electrical conductivity 98–101% IACS – negligible resistance contribution at joints
• Available in C11000, C10100, C12200 copper grades
• Threads to DIN 933, DIN 931, ISO 4017, ISO 4014, IS 1363, ASME B18.2.1
• M3–M36 / 1/4″–1-1/2″ standard range; custom sizes available
• Surface options: bare, tin-plated, silver-plated, nickel-plated
• Manufactured under ISO 9001:2015 QMS
• Full material test reports (MTR), dimensional inspection certificates available
• Non-magnetic, non-sparking, corrosion-resistant

Non-Magnetic and Non-Sparking Properties

Copper bolts are fully non-magnetic (permeability ≈ 1.0), making them essential in CT (current transformer) brackets, magnetic shielding enclosures, MRI-adjacent panels, and explosive-atmosphere (ATEX Zone 1/2) electrical installations where sparking fasteners create ignition risk. Non-sparking copper fasteners are specified in mining, petrochemical, grain handling, and munitions facilities per ATEX Directive 2014/34/EU and IS 8198.

Mechanical Properties

C11000 copper bolts: Tensile strength 200–250 MPa, Yield strength 60–180 MPa (depending on temper: annealed, half-hard, hard). Cold-headed bolts achieve higher yield through work hardening without alloying additions that reduce conductivity. For higher strength with conductivity, chromium-copper (C18200, ~80% IACS, ~450 MPa UTS) and cadmium-copper (C16200) fasteners are available on request for overhead line fittings and high-tension earthing applications.

Suitability for Transformer and Switchgear OEMs

Power transformer manufacturers (OEMs) specify copper bolts for core clamping, HV/LV winding terminal connections, tank earth studs, buchholz relay mounting, cooling radiator manifolds, bushing clamps, and tap-changer stud connections. In switchgear, copper set screws are used in isolator jaw assemblies, bus-riser connections, earth bus joints, cable termination lugs, surge arrester bases, and outdoor CT/PT mounting hardware. Dimensional interchangeability with standard hex bolts ensures fit-for-purpose replacement in maintenance applications.

Compliance with International Quality Standards

All copper fasteners are supplied with EN 10204 3.1 material test certificates, dimensional inspection reports per ISO 3269, hardness test reports (Vickers HV), and surface coating thickness records. Lot traceability from raw material to finished product is maintained. Export documentation (NABL-accredited lab reports, Certificate of Origin, packing lists) is provided for international shipments to the USA, UK, Germany, UAE, South Africa, Australia, and Southeast Asia.

Pricing and Commercial Terms

Copper bolts and hex set screws are priced at USD 16.80 per kilogram (EXW Jamnagar, India). Pricing is subject to LME copper price variation. Volume discounts apply for orders above 100 kg. MOQ: 10 kg per size. Payment: T/T 30% advance, balance against B/L copy.

Technical Specifications

Raw Material Grades and International Equivalents

Product Variants

Applications in Industry

Manufacturing Process

Copper bolts and hex set screws are manufactured using two primary processes: cold heading (for smaller sizes M3–M16) and hot forging + CNC machining (for larger sizes M16–M36). Cold heading uses drawn copper rod fed through multi-stage heading dies to form the hex head without material removal, achieving tight dimensional tolerances and work-hardened mechanical properties. For hot-forged copper bolts, round bar is cut to billet, heated to 700–850°C, pressed in closed dies, trimmed, then thread-rolled or thread-cut. CNC thread rolling produces stronger threads with work-hardened flanks compared to cut threads. Heat treatment (annealing at 400–600°C) is applied when softened (high-conductivity) temper is required. All fasteners are 100% dimensionally inspected, with periodic tensile and hardness testing per ASTM F606 / IS 6623.

Quality Standards and Certifications

Why Choose Electrical Accessories India

• Dedicated copper fastener manufacturing with in-house cold heading, machining and thread rolling
• Three copper grades stocked (C11000, C10100, C12200) for immediate order fulfilment
• Full traceability – heat number, chemical analysis, mechanical test data per lot
• Export experience to 40+ countries including USA, UK, UAE, Germany, Australia, South Africa
• Competitive pricing at USD 16.80/kg with volume discount structure
• Customisation – special lengths, non-standard threads, plating options, custom head styles
• Fast lead times – 2–4 weeks standard, expedited available for critical projects

Frequently Asked Questions (FAQ)

1. What is the difference between C11000 and C12200 copper bolts?

C11000 (ETP) has higher conductivity (100% IACS) and is standard for electrical applications. C12200 (DHP) has slightly lower conductivity (~85% IACS) but is phosphorus deoxidised, making it weldable and brazeable – preferred when the bolt assembly requires subsequent brazing or welding.

2. Can copper bolts replace stainless steel bolts in transformer terminals?

Yes. Copper bolts are preferred over stainless steel at transformer terminals because they eliminate the galvanic couple between dissimilar metals (copper conductor + stainless steel bolt), reduce joint resistance, and avoid potential stress corrosion cracking in stainless steel in the presence of chlorides or sulphur compounds.

3. What surface finish is recommended for coastal substation installations?

Tin-plated copper bolts (3–8 µm tin, electrodeposited per IEC 60068-2-52) are recommended for coastal, tropical, and salt-fog environments. The tin layer prevents copper surface oxidation while maintaining excellent contact conductivity.

4. Are copper hex set screws available in left-hand thread?

Yes, left-hand thread versions can be manufactured for specific applications (meter couplings, turnbuckles, specific motor terminal connections). Please specify thread direction in your enquiry.

5. What torque values apply to M12 copper hex bolts?

Recommended tightening torque for M12 copper hex bolts (C11000, bare): approximately 25–35 Nm for busbar joint applications, depending on contact material and surface preparation. Always verify with your joint design engineer; copper’s lower yield strength compared to Grade 8.8 steel requires careful torque management to avoid thread stripping.

6. Do you supply copper bolts with washers and nuts as a kit?

Yes. Copper fastener kits including hex bolt + flat washer + spring washer + nut can be supplied in matched sets. Kit pricing available on request.

7. What is the maximum temperature rating for copper fasteners?

Bare copper fasteners can operate continuously up to 105°C (standard electrical insulation class E). Tin-plated copper bolts are rated to 150°C; silver-plated to 250°C. At higher temperatures, chromium-copper (C18200) fasteners are recommended.

8. Are your copper bolts RoHS and REACH compliant?

Yes. C11000, C10100, and C12200 copper alloys contain no restricted hazardous substances under RoHS Directive 2011/65/EU or REACH Regulation (EC) 1907/2006. Compliance declarations available on request.

9. What is the minimum order quantity?

Minimum order is 10 kg per size/grade combination. For trial/sample orders below 10 kg, a small-order surcharge applies. Contact our sales team for MOQ flexibility on specific projects.

10. Can you provide UL-listed or CE-marked copper fasteners?

Our copper fasteners are manufactured to the dimensional and material standards required for UL and CE compliance. We provide EN 10204 3.1 material test certificates and dimensional inspection reports to support your component compliance documentation. Product-level UL listing is not held but can be pursued for large OEM supply programmes.

Equivalent Terms and Multilingual Reference

Related Products and Linked Terms

• Brass Machine Screws
• Brass Panel Nuts
• Silicon Bronze Hex Nuts
• Silicon Bronze Bolts
• Brass DIN 934 Hex Nuts
• Brass Standoffs
• Brass Spacers
• Brass Thumb Screws
• Copper flat washers, copper spring washers, copper hex nuts, copper stud bolts, copper earthing bolts, copper terminal screws

Request a Quote

Electrical Accessories India supplies copper bolts and hex set screws to electrical OEMs, EPC contractors, power utilities, and distributors worldwide. Pricing: USD 16.80 per kilogram (EXW Jamnagar, India). For bulk pricing, custom specifications, and technical support, contact our engineering sales team.

Email: info@elecaccs.com | Location: Jamnagar, Gujarat, India | Export Markets: USA, UK, UAE, Germany, Australia, South Africa, Brazil, Southeast Asia

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