Copper 110 (C110) CNC Machining

What the 101% means

The IACS scale sets annealed pure copper at 100% conductivity. Copper 110 is specified at around 101% IACS — marginally above the reference, which is possible because the reference itself is a nominal figure and modern ETP copper measurably exceeds it.

What matters commercially is not the percentage point but the gap to everything else. Nothing in the copper family comes close: the brasses sit at roughly 28% IACS, and the bearing bronzes lower still. So when conductivity is the reason the part exists, the material decision is effectively already made, and the remaining questions are about which copper and how to machine it.

	Copper 110	Copper 101	Brass 360
Copper content	99.90% min	99.99% min	~60–63%
Oxygen	0.02–0.04% (as oxide)	Below ~5 ppm	—
Conductivity	~101% IACS	~101% IACS	~28% IACS
Chosen for	Standard electrical and thermal duty	Vacuum, RF and reducing-atmosphere service	Machinability
Machining	Poor, but slightly easier than 101	Poor — no oxide to break the chip	100% reference

Copper 110 is the working grade: cheaper than the oxygen-free material, adequate for almost every conductor and thermal application, and marginally easier to cut because the oxide particles interrupt the chip.

Where 101 takes over

The difference between copper 101 and 110 is oxygen, and it is worth understanding because it is not a subtle metallurgical curiosity — it is a failure mechanism.

Electrolytic tough pitch copper contains a small controlled amount of oxygen, present as copper oxide particles at the grain boundaries. That is normally harmless. But if the metal is heated in a reducing atmosphere — as happens in some brazing and welding processes — hydrogen diffuses into the copper, reaches the oxide particles, and reacts with the oxygen to form steam.

Steam cannot escape from inside a solid. The pressure builds at the grain boundaries, and they crack. That is hydrogen embrittlement, and it is the reason oxygen-free copper 101 exists.

So the rule is:

• Cut, formed, or used at ambient temperature — copper 110 is the sensible choice
• Brazed or welded in a reducing atmosphere, or used in vacuum or RF service — copper 101, and say so at the enquiry

The other difference is conductivity specification: 101 is held to a marginally higher minimum, which matters in high-reliability electrical and microwave work where every fraction of a percent is designed in.

Machining copper: the specific problems

Copper is one of the more awkward materials in the shop, and it is awkward for reasons that are the exact opposite of steel’s.

The chip will not break. Copper is soft and extremely ductile, so it produces long continuous chips that tangle the tool, wrap the workpiece and are a handling hazard. On a finishing pass the chip drags across the surface that was just produced.

The edge builds up. Copper welds to the cutting edge readily. The built-up material rounds the edge geometry, degrades the finish, and then breaks away unpredictably, often taking part of the edge with it. This is the single largest cause of poor finish on copper work.

It work-hardens. Like the austenitic stainless grades, copper hardens as it is deformed, so a light spring pass rubs and hardens the surface rather than removing it. The answer is the same: a decisive depth of cut.

It conducts heat into the workpiece. Copper’s thermal conductivity is extremely high, so the heat generated by cutting moves into the part rather than concentrating at the edge. Two consequences: tool life is generally good, and the part gets warm and expands. A dimension measured on a hot copper part can read correct and then come in undersized when it cools. Critical dimensions belong on a cooled part, with coolant used to keep the workpiece temperature stable.

What works on copper:

• Sharp, high-rake, polished-flute tooling. Rake angle matters more here than on any other material we run — copper will not tolerate a blunt edge
• Generous feed per tooth, so the edge shears under the deformed layer instead of burnishing
• Higher surface speeds than feel right. Running slowly is what lets built-up edge take hold
• Flood coolant, primarily to control workpiece temperature and to flush chips clear
• Rigid workholding, because copper is soft enough to be marked by the clamp as well as by the tool

Copper is generally supplied annealed or in a hard temper, and the temper changes how it cuts. Where the drawing specifies a temper rather than “copper”, that is worth noting at the enquiry.

Precision features are held to ±0.01 mm with ISO 2768-m as the general tolerance block — see tolerances we hold.

Corrosion: it does not corrode away

Copper’s corrosion behaviour is unusual and worth knowing for anyone specifying a part that will be visible.

It oxidises to a brown surface and then, over time and with moisture exposure, develops a green patina — verdigris — that adheres to the metal and protects it. Copper roofing and flashing last for generations on this basis. Unlike the rust on a steel part, the patina is not a failure; it is a stable, self-limiting layer.

The practical implications:

• A part left bare will change colour, from bright copper through brown to green depending on atmosphere and time. That is either the design intent or a problem, and it should be decided rather than discovered.
• Where a part must stay bright, it needs a lacquer or a plating — nickel or tin are the usual choices for electrical work, silver where contact resistance matters.
• In aggressive environments, copper still performs well, but it can be attacked by ammonia and by some sulphur compounds. Say what the part touches.

Where copper 110 is the right choice

• Busbars and current-carrying conductors of all kinds
• Terminals, lugs and electrical contacts
• Heat-exchanger and thermal-management components, where the high thermal conductivity is doing the work
• Gaskets and sealing rings in copper
• Waveguides, RF cavities and antenna components, where 101 is not required
• Electrodes and electrical discharge machining electrodes, though electrode work has its own trade-offs
• Architectural roofing, flashing and cladding, where the patina is part of the design
• Any part where conductivity is the design driver and the electrical duty is not in the high-reliability category

Where copper 110 is the wrong choice

The part will be brazed or welded in a reducing atmosphere, or used in vacuum. The oxygen content is a hydrogen-embrittlement risk. Specify copper 101 and say so.

The part is a turned item produced in volume. Copper is one of the slowest materials we cut. Where the conductivity requirement is modest, brass 360 cuts several times faster at roughly a quarter of the conductivity — and where a bushing or bearing is needed, bronze is the family.

The part is a bearing or a wear surface. Pure copper is soft and has poor bearing properties. The bearing bronzes exist for exactly this duty.

A tight tolerance without temperature control. Copper’s expansion under cutting heat will move a dimension. Where a part is close-tolerance and the machine cannot hold a stable workpiece temperature, that has to be planned rather than assumed away.

Cost is the binding constraint and conductivity is not. Copper is expensive and slow. Verifying that the electrical requirement genuinely needs 101% IACS is worth doing before the drawing is released.

Finishing copper 110

Copper is usually finished for one of three reasons: to hold a bright appearance, to control contact resistance, or to make a surface solderable.

• Nickel plating — a hard barrier layer that also stops the surface tarnishing, and the standard under-layer for gold on electrical contacts
• Tin plating — a common, solderable, corrosion-resistant finish on busbars and terminals
• Silver plating — the lowest contact resistance for electrical joints, at a cost
• Polishing and brushing — copper takes a high polish, and on decorative work this is the specification
• Lacquering — the way to hold a bright copper finish on a visible part
• Tumbling and deburring — the standard route on small parts

A note specific to copper and plating: because copper is so soft, deburring has to be controlled carefully — an aggressive tumble or brush will round the edges of a part that was machined to a sharp corner on purpose. Where a sharp edge is functional, say so.

All finishing runs through our vetted partner network, managed under one quality process. The grades we run across every process are listed on the materials page.

What to put on the drawing

Instead of	Write
Copper	Copper 110 (C110), or 101 if it will be heated in a reducing atmosphere
Copper 110, will be vacuum-brazed	Wrong grade — the oxygen content causes hydrogen embrittlement
Copper 110, tight tolerance	Say which dimensions matter — copper expands under cutting heat
Copper 110, turned part in volume	Expect a slow cut — brass 360 is far faster if conductivity allows
Copper 110, bearing or wear surface	Wrong grade — copper is soft. Use a bearing bronze
Copper 110, must stay bright	State the finish — bare copper patinates
Copper 110, sharp edges functional	Say so — deburring has to be controlled on soft copper
Copper 110, high-reliability or RF duty	Copper 101 carries the higher conductivity specification

The two lines that decide most copper 110 specifications are whether the part will be exposed to a reducing atmosphere and how much conductivity the design actually needs. The first picks between 110 and 101 and is a genuine failure risk if it is missed. The second decides whether a copper alloy is needed at all.

Material is bought against your drawing for your job, and every batch ships with a material certificate (MTR) tracing the grade to its mill heat plus pre-shipment photos of the actual parts. Orders start at 50 pieces per style and material, samples from a single piece in 5–10 days, and production runs in 25–35 days after sample approval. Send the drawing through the request a quote form and the reply comes back within 24 hours with DFM feedback — including a note on the temper, the joining route and the deburring where either applies.