Copper Machining and Fabrication Suppliers in Eau Claire, WI: C101, C110, and Tellurium Copper

C101 (Oxygen-Free Electronic copper, OFE) achieves minimum 99.99% copper purity and a conductivity rating of 101% IACS. The absence of oxygen prevents hydrogen embrittlement in high-temperature or reducing-atmosphere applications, making C101 the preferred grade when copper components will be brazed, welded, or operated at elevated temperatures in hydrogen-containing environments. Vacuum electron devices, waveguide components, and high-reliability electrical feedthroughs specify C101 when purity and conductivity at the absolute maximum matter. Eau Claire suppliers sourcing C101 for medical or defense applications should confirm that material certifications trace to ASTM B170 and that the oxygen content is documented in the mill test report. C110 (Electrolytic Tough Pitch copper, ETP) is the standard commercial copper grade, with minimum 99.9% purity and 100% IACS conductivity. It is the most widely available copper product in bar, plate, sheet, tube, and rod forms at metal service centers across western Wisconsin. Bus bars, grounding straps, electrical terminals, heat sinks, and formed sheet metal components for electrical equipment all default to C110 when the application does not require the extreme purity of C101 or the machining characteristics of a tellurium copper. C110 is softer than tellurium copper and presents machining challenges: its gumminess causes built-up edge on cutting tools and torn rather than sheared chip formation if tooling geometry and speeds are not optimized. Tellurium copper (C145) adds approximately 0.4 to 0.7% tellurium to the base copper, which dramatically improves machinability without materially reducing conductivity (minimum 93% IACS). C145 is the machine shop's copper: it chips freely, produces tight turnings rather than the long stringy chips that plague C110 machining, and holds tighter tolerances because it does not smear. Precision electrical contacts, connector pins, valve stems, and turned components with multiple intersecting bores are produced in C145 by Eau Claire shops that run high-volume copper work on CNC Swiss or multi-spindle lathes.

Copper's machining behavior is counterintuitive to machinists accustomed to steel. Despite being a soft metal, pure copper grades (C101 and C110) are notoriously difficult to machine cleanly because they are highly ductile and sticky. Instead of forming clean chips, they tend to smear onto tool faces, produce built-up edge on insert geometry, and generate poor surface finishes even with aggressive cutting parameters. The solution is sharp tooling with high positive rake angles — polished high-speed steel (HSS) tools with 15 to 20 degree positive rake, or uncoated or diamond-coated carbide with similar geometry. Coatings designed for steel or aluminum (TiN, TiAlN) are generally counterproductive on copper because the adhesion chemistry worsens smearing. Cutting speeds for C110 copper with sharp carbide tooling run 800 to 1,500 sfm on turning operations, using a dry cutting approach or light mist coolant rather than flood coolant for most operations. Flood coolant can actually worsen copper machining by washing chips back into the cut rather than clearing them. The key is chip control: C110 produces long stringy chips at slow speeds and feeds, which must be broken by geometry or interrupted cutting cycles to prevent chip wrap around the workpiece. Tellurium copper C145, by contrast, machines more like free-cutting brass at similar parameters, producing short chips and clean surfaces with significantly less tool management complexity. For CNC turning of copper bus bar components — hexagonal or rectangular cross sections being turned to precise diameters, undercuts, and threaded features — Eau Claire shops running Swiss-type lathes achieve excellent results on C145 at part tolerances of plus or minus 0.001 inch on diameters and 0.003 inch on length. High-volume connector pin production from C145 bar stock is well within the capability of Chippewa Valley shops serving the electrical equipment assembly market.