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 comparison, 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.
Check price on Amazon →We evaluated 7 copper alloys and stock forms for machinability, surface finish quality, and value. Here is what experienced machinists should be buying.
Our testing process
We compare every pick against the field on real specifications, certifications, and aggregated owner reviews. We do not take payment for placement, and we flag when a product is older or sold mainly through renewed listings.
Quick comparison
| Pick | Best for | Score | |
|---|---|---|---|
| Tellurium Copper C14500: the best copper alloy for machinability | Check price | ||
| C110 Electrolytic Copper: the runner-up for maximum conductivity requirements | Check price |
Reviewed in detail
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 comparison, 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.
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.
How to choose
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.
Common questions
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.
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.
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.
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.