Copper Machining Glossary

A heat treatment that strengthens certain copper alloys by precipitating a second phase from solution after a solution treatment and quench.

Beryllium, chromium and zirconium coppers get their strength this way. The temper code tells you whether it has been done.

Copper temper codes explained

Copper that has been softened by heating and controlled cooling, designated O60 or O61 under ASTM B601.

Bends easily, machines gummily, marks in the vise. Order it for forming, not for machining.

The ASTM specification for copper sheet, strip, plate and rolled bar, covering C10100, C10200, C11000, C12200 and others.

Name it on a drawing when the part is cut from plate.

The ASTM specification for copper bus bar, rod and shapes, and general purpose rod, bar and shapes.

The usual callout for busbar and for machined parts from bar.

The ASTM specification for free-cutting copper rod, bar, wire and shapes, covering C14500, C14700 and C18700.

If you are specifying tellurium or sulphur copper, this is the standard.

The ASTM classification of temper designations for wrought and cast copper and copper alloys.

Every O, H and T temper code on a copper drawing comes from this document.

Workpiece material that welds itself to the cutting edge under pressure and heat, changing the effective tool geometry.

The main cause of smeared finish and heavy burrs on copper. Cured with sharp high rake tooling and a real feed rate, not by slowing down.

Why copper is difficult to machine

A raised lip of material left at an edge where the tool exits the workpiece.

Copper burrs on almost every exit edge because it stretches instead of fracturing. On thin parts deburring can take longer than cutting.

Deburring copper parts

A solid conductor, usually a flat copper bar, that distributes current inside switchgear, panels, battery packs and equipment.

Mostly metal with a little machining. Price is set by cross section, holes, bends and plating.

Copper busbar machining

Oxygen free electronic copper, 99.99 percent copper, about 101 percent IACS.

Specified for vacuum, hydrogen brazing and EDM electrodes. About one point more conductive than C110.

C10100 reference page

Electrolytic tough pitch copper, the default electrical copper at about 100 percent IACS.

Contains a little oxygen as copper oxide, so it embrittles in hydrogen and is not used for ultra high vacuum.

C11000 reference page

Tellurium copper, a free-machining copper at about 93 percent IACS with a machinability rating near 85.

The largest single cost lever in copper machining when the conductivity requirement has headroom.

C14500 reference page

Chromium copper, an age hardened alloy at about 80 percent IACS, RWMA Class 2.

The general purpose resistance welding electrode material.

C18200 reference page

A machined plate with internal channels through which coolant flows to remove heat from components mounted on it.

In copper, usually a two piece brazed design or a drilled and plugged block. State the joining method and leak test in the RFQ.

Copper heat sink and cold plate machining

The ability of a material to carry electric current, expressed for copper alloys as a percentage of the IACS reference.

Copper grades run from about 22 percent IACS for beryllium copper to 101 percent for oxygen free copper.

Phosphorus deoxidized copper, high residual phosphorus, UNS C12200, about 85 percent IACS.

The brazing and tube grade. The phosphorus costs conductivity.

C12200 reference page

The material specification line on an engineering drawing: name, UNS number, ASTM specification for the product form and temper.

Four elements. Anything missing is a decision handed to the shop.

How to specify copper on a drawing

A process that erodes conductive material with controlled electrical sparks between an electrode and the workpiece.

Sinker EDM electrodes are commonly machined from C10100 copper or graphite.

Copper EDM electrodes

An electrochemical process that removes a thin surface layer, leaving a bright smooth surface and rounding micro burrs.

Common on vacuum parts. It removes material, so the tolerance has to allow for it.

Electrolytic tough pitch copper, UNS C11000. See C110.

C11000 reference page

Fin height divided by the gap between fins, on a heat sink.

Past roughly 10 to 1 the cutter deflects, the shop slows down and the price rises faster than the geometry.

Designing a machined copper heat sink

A full dimensional and documentary inspection of the first part produced against the drawing, before the batch continues.

Real hours after the part exists. Ask for it in the RFQ, not after shipment.

A copper with a small addition of tellurium, sulphur or lead that breaks the chip, raising machinability from about 20 to about 85.

C14500, C14700 and C18700. Not for ultra high vacuum.

A cold worked temper under ASTM B601, the usual default for busbar stock and machined plate.

Stiff enough to hold under clamping, machines better than annealed, still bends at a sensible radius.

A cold worked temper under ASTM B601, standard for drawn free-machining rod.

Best surface finish, least formable. Hard copper cracks at a tight bend radius.

The identifier of the melt a piece of material came from, linking it to its material certificate.

Without a heat number traceable to the delivered bar, a certificate is a statement of intent.

How to read a copper material certificate

Internal cracking that occurs when oxygen bearing copper is heated in hydrogen, as the hydrogen reacts with copper oxide to form steam inside the metal.

The reason C10100 is specified for hydrogen furnace brazing and C11000 is not.

Oxygen free copper for vacuum and UHV

International Annealed Copper Standard, the reference against which electrical conductivity is expressed as a percentage.

Annealed pure copper was defined as 100 percent. Modern oxygen free copper slightly exceeds it.

A qualified request for quotation passed to a supplier, who pays for the opportunity rather than for an order.

On this site, each RFQ goes to at most three shops. A lead is not an order.

How machine shops actually find copper work

A relative score for how easily an alloy cuts, with free-cutting brass C36000 defined as 100.

Pure copper rates about 20, free-machining copper about 85. It predicts chip behaviour, not burrs or finish.

What a machinability rating actually tells you

An intermediary that reads a buyer request and passes it to a small number of suppliers who fit, without taking part in the order.

What this site is. We do not own machines and take no commission.

How we match

A document from the material supplier stating the alloy, chemistry, mechanical properties and heat number of the delivered material.

EN 10204 type 3.1 is the one most specifications mean by certified material.

Copper material certificates

Non-disclosure agreement, a contract restricting how a party may use and share confidential information such as drawings.

Ask for one on the RFQ form and files are held until the shop has signed it.

Oxygen free electronic copper, UNS C10100. See C101.

C10100 reference page

The slow release of gas from a material into a vacuum, which limits the pressure a system can reach.

Oxide inclusions and trapped contaminants outgas. Oxygen free copper and clean handling reduce it.

Electrical conductivity expressed as a percentage of the International Annealed Copper Standard.

The number to put on a drawing when you want to leave the grade open: minimum 90 percent IACS, for example.

A thin metal layer deposited on a part, on copper usually tin, nickel or silver, for corrosion protection and a stable contact surface.

Specify finish, thickness for contact and non-contact areas, plated and masked areas, and whether dimensions apply before or after.

Tin, nickel or silver plating on copper

The arithmetic mean deviation of a surface profile from its mean line, the most common surface finish measure.

Machined copper is typically Ra 1.6, Ra 0.8 with a finishing pass. Specify it per face, not per part.

Copper surface finish

Request for quotation, the package of drawing, quantity and requirements a buyer sends to get a price.

The RFQ builder writes the specification lines for a copper part.

Copper RFQ builder

The EU Restriction of Hazardous Substances directive, which limits lead and other substances in electrical and electronic equipment.

Relevant to leaded copper C18700 and to free-cutting brass C36000.

A classification of resistance welding electrode materials by the Resistance Welding Manufacturers Alliance.

Class 1 zirconium copper, Class 2 chromium copper, Class 3 nickel beryllium copper, Class 4 beryllium copper. Group B is refractory.

RWMA classes for copper welding electrodes

The tendency of alternating current to concentrate near the surface of a conductor, more so at higher frequency.

Why surface finish is an electrical property on RF copper parts, and why busbar thickness has diminishing returns on AC.

A process that peels fins from a solid block with a blade, producing a one piece fin pack with no joints.

Usually cheaper than machining a plain straight fin pack at volume.

An age hardenable alloy heated and quenched so its hardening elements are held in solution, the soft condition before ageing.

The condition to machine in when you want an easier cut, accepting a small dimensional change on ageing.

The distance between electrode and workpiece across which discharges occur, which the electrode must be undersized to allow for.

The drawing must say whether the gap offset is already applied. Most scrapped electrodes are that line missing.

The condition of a copper alloy resulting from its mechanical or thermal processing, designated under ASTM B601.

Sets strength, bend radius, machining behaviour and, on age hardening alloys, conductivity. A grade without a temper is half a specification.

Copper temper codes explained

The fully aged temper of an age hardening copper alloy, with final strength, hardness and conductivity.

Slower to cut than TB00, but dimensions hold.

A temper that is both cold worked and precipitation hardened, the usual delivery condition for welding electrode alloys.

Vacuum below roughly 10 to the minus 7 pascal, where system pressure is limited by outgassing from the walls.

Oxygen free copper, no trapped volumes, no burrs, vacuum clean handling.

Oxygen free copper vacuum components

A Unified Numbering System designation that identifies an alloy exactly, for copper alloys a C followed by five digits.

Copper is not a specification. C11000 is.

Copper grade reference

A trapped pocket of gas inside a vacuum envelope, typically under a bolt in a blind tapped hole, that bleeds out slowly and mimics a real leak.

Prevented with vent holes or vented screws. Mark the vacuum boundary on the drawing.

A hollow metal conductor that guides electromagnetic waves, usually rectangular, with internal surface finish setting the loss.

Copper RF, waveguide and cavity parts

The increase in strength and hardness of a metal as it is plastically deformed.

Why a rubbing tool on copper makes the next pass harder, and why cold worked tempers machine better than annealed.