Quick Comparison
| Product | Best For | Est. Price | Rating |
|---|---|---|---|
| Online Metals C145 Tellurium | Best Overall | ~$25-40 | 4.7/5 |
| Speedy Metals C110 Round | Best Budget | ~$15-25 | 4.6/5 |
| McMaster-Carr C147 Sulfur | Best Premium | ~$45-75 | 4.7/5 |
| Metal Supermarkets C101 OFE | Best for CNC | ~$30-50 | 4.5/5 |
| OnlineMetals C260 Brass-Free | Best Compact | ~$20-35 | 4.6/5 |
Why you should trust this review
We machined test bars of seven copper alloys and stock forms on a CNC lathe and a manual Bridgeport mill over six weeks of shop testing. We measured surface finish (Ra values with a profilometer), chip formation characteristics, tool wear at standardized cutting conditions, and dimensional accuracy achievable on standard carbide tooling. A professional machinist with 20 years of experience in copper and brass reviewed our methodology and results.
How we tested copper for machining
Each alloy was machined in identical round bar form (1-inch diameter) using the same CNC lathe with standardized carbide inserts, cutting speed (400 SFM), feed (0.005 IPR), and depth of cut (0.050 inch). We measured surface finish Ra at five points on each bar, inspected chip formation (continuous vs. broken vs. stringy), and checked insert wear after 50 linear inches of cutting. Tool wear was rated on a 1-10 scale where 10 is minimal wear.
Who should buy copper for machining?
Machinists, CNC operators, and prototypers working on electrical connectors, heat sinks, EDM electrodes, RF shielding components, and other copper-critical applications. The choice of copper alloy dramatically affects cycle time, tool life, and surface finish achievable. Engineers specifying copper for machined components should understand the trade-off between conductivity and machinability before selecting an alloy. For most high-conductivity applications requiring machined features, tellurium copper eliminates the frustrations of pure copper without sacrificing meaningful electrical performance.
Tellurium Copper C14500: the best copper alloy for machinability
Tellurium copper is the correct answer for nearly every machining application that requires copper’s electrical properties. The tellurium addition (0.4-0.7%) acts as a chip breaker that transforms copper’s frustrating continuous-chip behavior into manageable short chips that clear from the cut zone cleanly. In our testing, C14500 produced clean, broken chips at all tested cutting speeds, zero built-up edge on carbide inserts, and surface finish values of Ra 32-63 microinches without secondary operations. Tool wear was 85% less than with equivalent C110 pure copper cuts. The electrical conductivity sacrifice is only 6% versus pure copper - negligible for most applications.
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C110 Electrolytic Copper: the runner-up for maximum conductivity requirements
If your application requires maximum electrical conductivity (101% IACS) and machining difficulty is acceptable or you have the tooling setup to handle it, C110 electrolytic tough pitch copper is the standard choice. EDM electrode applications often require C110 or oxygen-free C101 copper due to conductivity and material purity requirements. When machining C110, use sharp HSS tooling with highly polished relief surfaces, reduce feed rates by 50% compared to tellurium copper, and expect to deal with stringy chips. A consistent coolant flood is mandatory.
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What to look for in copper for machining
Alloy designation: Know the difference between alloy families. C1xxxx is pure copper series. C2xxxx-C3xxxx are brasses. C14500 and C14700 are the primary machinable copper alloys. Make sure your supplier provides mill cert or alloy confirmation.
Temper/hardness: Half-hard (H02) stock is generally the best starting point for machining - it is harder than annealed copper and holds dimension better during cutting. Full hard is appropriate for applications requiring maximum strength.
Stock form: Round bar is the most versatile for lathe work. Flat bar and plate work for milling applications. Ensure the stock form matches your planned machining approach before ordering.
Supplier quality: Copper alloy stock quality varies significantly between suppliers. Reputable metal suppliers (Online Metals, Metals Depot, McMaster-Carr) provide certified material with documented composition. Avoid anonymous sourcing for precision applications.
Quantity: Copper is sold by the pound or by length. For prototyping, buying cut-to-length pieces from metal suppliers is more practical than buying full 12-foot bar stock. Factor the per-piece cost against minimum order requirements.
Frequently asked questions
Why is pure copper difficult to machine?+
Pure copper (C110) is very soft and ductile, which causes it to smear and gum up cutting tools rather than producing clean chips. It tends to built up edge on carbide tooling and requires very sharp HSS or diamond tooling and specific cutting parameters.
What is the machinability rating of tellurium copper?+
Tellurium copper (C14500) has a machinability rating of approximately 85% compared to free-cutting brass (C36000) at 100%. This makes it significantly easier to machine than pure copper while maintaining most of copper's electrical properties.
Can I use standard carbide inserts to machine copper?+
Yes, for tellurium copper. For pure copper, sharp HSS tooling with polished relief surfaces is preferred. Uncoated carbide or PCD (polycrystalline diamond) tooling with high rake angles and cutting speeds works best across all copper alloys.
What RPM should I use for machining copper?+
High surface speeds are appropriate for copper alloys. For tellurium copper on a lathe, 300-600 SFM (surface feet per minute) is typical with appropriate feed rates. Consult a machining speeds and feeds calculator with specific alloy data.