Copper Alloy Sourcing and Precision Machining in Fond du Lac, WI

Commercial copper for manufactured components comes in grades differentiated primarily by purity, oxygen content, and alloying additions that modify machinability. Selecting the correct grade requires understanding how downstream processing — welding, brazing, soldering, machining, or electroplating — interacts with the copper's chemistry. C101 (oxygen-free high conductivity, OFHC) is produced with oxygen content below 0.001 percent, giving it electrical conductivity of 101 percent IACS — the highest of any commercial copper grade. The absence of oxygen prevents the embrittlement that occurs when conventional copper is heated in hydrogen-containing atmospheres, where dissolved oxygen at grain boundaries reacts with hydrogen to form steam pockets (hydrogen embrittlement). For applications that involve hydrogen furnace brazing, welding with hydrogen shield gas, or high-purity vacuum environments, C101 is the required grade. Electrical bus bars, vacuum tube components, and high-frequency waveguide components in the Fond du Lac region specify C101 for these combined conductivity and processing reasons. C110 (electrolytic tough pitch, ETP) is the workhorse commercial copper grade, with 99.9 percent copper minimum and conductivity of 100 percent IACS. It is less expensive than C101 because it is produced without the specialized deoxidation process, and its small oxygen content (0.02 to 0.04 percent) does not affect performance in normal manufacturing environments. C110 is widely available in sheet, strip, bar, rod, and tube forms from Midwest distributors serving the Fox Valley, and it is the default specification for copper bus bars, transformer windings, roofing and architectural copper, and general electrical components that will not see hydrogen atmosphere processing. Tellurium copper (C145, approximately 0.5 percent tellurium) trades a small reduction in conductivity (93 to 95 percent IACS) for dramatically improved machinability — tellurium acts as a chip-breaker, transforming copper's normally gummy, long-chip behavior into short, breaking chips that evacuate cleanly from drills, taps, and turning tools. For screw machine production of electrical connectors, terminal pins, switchgear components, and small bushings requiring tight tolerances and high production rates, tellurium copper is the standard choice. The conductivity reduction from pure copper is negligible in most connector and terminal applications. Shops running Swiss-turn machines or screw machines in the Fox Valley specify C145 as a matter of production efficiency.

Machining pure copper grades (C101 and C110) presents a distinct set of challenges compared to the structural metals that dominate most shop floors. Copper's high ductility — elongation at break of 45 percent or more — means it deforms plastically rather than fracturing cleanly during cutting, producing long, stringy chips that tangle around tooling, clog flutes, and re-cut, causing built-up edge and poor surface finish. Managing this behavior requires sharp tooling with high positive rake angles (15 to 20 degrees), high cutting speeds that generate enough shear energy to produce clean chip separation, and flood coolant that lubricates the cut and carries chips away. High-speed steel tooling remains viable for copper machining at moderate speeds because copper's relatively low hardness (Brinell 40 to 50 for annealed C110) does not require carbide hardness for tool survival. Carbide tooling with polished rake faces and sharp edges runs at higher speeds and provides better surface finish on final cuts. For CNC turning of C110 bus bar stock to ±0.001 inch diameter tolerances, consistent feed rates and sharp tooling produce Ra 32 microinch or better surface finishes on the turned OD without requiring separate polishing operations. Drilling copper is particularly prone to chip-packing and drill wandering: the gummy chip tends to pack in flutes on deep-hole drilling operations, stalling drills and overheating the workpiece. Shops use split-point drills with polished flutes, peck drilling cycles that clear chips every 1 to 2 diameter depths, and cutting oils with good lubricity to manage these tendencies. For tapped holes in copper, plug or spiral-flute taps with good flute geometry minimize the torque spikes that cause tap breakage. Tellurium copper (C145) largely eliminates these challenges — its chip-breaking behavior allows drilling and tapping at speeds and feeds closer to those used on brass, making it the preferred specification whenever conductivity requirements permit the small penalty.

Fond du Lac's manufacturing economy connects copper to a range of functional applications that reflect the city's industrial character. Mercury Marine's electrical systems and charging circuits use copper wiring harnesses and terminal hardware that must maintain low contact resistance through years of vibration, moisture, and temperature cycling. Marine-grade copper terminals are often silver-plated or tin-plated to prevent oxidation at connection points, with plating thickness of 0.0002 to 0.0005 inch for tin and 0.0001 to 0.0002 inch for silver on contact surfaces. Heavy-equipment manufacturing in the Fox Valley requires copper bus bars for control panel assemblies, inverter DC bus connections, and high-current motor drive systems. Bus bars are typically fabricated from C110 flat bar in cross-sections ranging from 0.25 by 1 inch for small panel boards to 0.5 by 4 inch for high-current inverter connections, punched or drilled for mounting hardware, with edges deburred and optionally tin-plated for connection surface protection. Shops supplying bus bar assemblies to heavy-equipment OEMs provide punching, drilling, bending, plating, and assembly in a single-source arrangement that reduces procurement complexity. Heat transfer applications in the Fox Valley's manufacturing base include copper tube sheets for shell-and-tube heat exchangers used in hydraulic oil cooling, compressed air cooling, and industrial process cooling. These components are machined from C110 plate with drilled tube holes in triangular or square pitch patterns, held to ±0.003 inch true position to ensure tube installation without distortion. Brazing copper tube-to-tube-sheet joints with phosphorus-copper or silver-copper filler alloys creates leak-tight connections with service life measured in decades. Shops with both machining and brazing capabilities in the Fond du Lac area can produce complete heat exchanger cores, reducing assembly steps and improving quality.