Copper Machining and Fabrication in Decatur, IL: C101, C110, and Tellurium Copper

C110 (electrolytic tough pitch copper) is the workhorse grade for electrical applications. Its minimum 99.9% copper content delivers electrical conductivity at 100% IACS — the benchmark to which all other conductive materials are compared. In Decatur's industrial context, C110 is specified for busbars in large electrical distribution panels, transformer leads, motor connection hardware, and any application where conductivity is the primary design driver. Its thermal conductivity of 226 BTU/hr·ft·°F makes it equally attractive for heat exchanger plates, heat sink blocks, and cooling components in industrial processing equipment. C110 is soft and machines easily at high surface speeds, but its ductility requires sharp tooling with positive rake geometry to prevent built-up edge and produce clean surface finishes. At cutting speeds of 500 to 800 SFM with proper tooling, C110 machines quickly and produces good surface finish. The challenge is workholding: copper's low yield strength (approximately 10,000 psi annealed) means soft jaws, collets, or dedicated fixtures are needed to avoid distorting the part during clamping. For thin-wall or close-tolerance C110 work, fixturing design is as important as cutting parameters. C110 plate, sheet, bus bar, and round bar are available from regional metals distributors with relatively short lead times — typically 1 to 2 weeks for standard sizes. Copper pricing is tied directly to the COMEX copper price, which fluctuates; lock your material cost at quote stage if the project timeline extends more than a few weeks.

C101 (oxygen-free high-conductivity copper, OFHC) takes electrical copper one step further by eliminating the trace oxygen content present in C110 ETP. The absence of oxygen prevents hydrogen embrittlement during welding or brazing operations and makes C101 suitable for high-vacuum applications, semiconductor processing equipment, and precision electrical contacts where the absolute highest conductivity (101% IACS) and purity are required. For most industrial applications in Decatur, C110 is sufficient; C101 is specified when the application involves vacuum brazing, high-frequency power conditioning, or precision electronic contact components where even trace oxygen is problematic. C101 machines identically to C110 and requires the same positive-rake tooling approach. The material premium over C110 is modest — typically 10 to 20% more per pound — but availability is more limited. Standard stock sizes may need 2 to 4 weeks from specialty distributors rather than the 1 to 2 weeks typical for C110. For busbars and heavy conductors in Decatur industrial facilities, C110 is nearly always the correct choice; C101 is reserved for electronic and vacuum applications where the oxygen-free specification is technically required. Brazing and soldering copper is common in heat exchanger and electrical assembly work. C101's oxygen-free character makes it particularly clean for torch or furnace brazing with silver brazes (BAg alloys), as there is no risk of outgassing during the brazing cycle. For food-processing-adjacent copper components — rare in Decatur but possible in water-system work — NSF 61 certified braze alloys are required for potable water contact.

Tellurium copper (C145, UNS C14500) is the answer to a specific problem: standard C110 copper machines poorly at tight tolerances because of its gummy, ductile character. The addition of 0.4 to 0.7% tellurium transforms copper's machinability dramatically — chip breaking improves, surface finish improves, and achievable tolerance tightens. C145 retains approximately 93% of C110's electrical conductivity while machining at nearly the efficiency of free-machining brass. For precision-turned electrical components — connector bodies, contact pins, terminal blocks, heat sink components with fine features, and threaded electrical fittings — C145 is the correct specification. Decatur's CNC turning shops that handle non-ferrous work encounter C145 in production runs of electrical and thermal components for industrial equipment. Bar-fed turning operations in C145 run at 600 to 900 SFM with carbide tooling, produce excellent chip control, and hold dimensional tolerances of ±0.001" on turned diameters without the galling and size deviation problems that pure copper presents. For components requiring tight bore fits or threads, C145 delivers results that are simply not achievable in C110 without specialized and slow processing. C145 is available in round bar from 1/4" through 4" diameter from copper specialty distributors, with lead times similar to C110 for standard sizes. It is not typically stocked in plate or sheet form; flat components requiring tellurium copper are usually machined from bar or purchased as custom extrusions. Confirm stock availability at time of quote for less common diameters.