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What Copper Temper Codes Change About Your Part

September 25, 2026

A grade without a temper is half a specification. Temper decides whether the bar you receive bends or cracks, whether the wall you machined stays where you put it and, on some alloys, what the part conducts. This is what the codes mean in practice.

Where the codes come from

Temper designations for copper follow ASTM B601, which classifies them by the process used to produce the condition. Three families cover machined work.

O tempers are annealed, produced by heating and controlled cooling. H tempers are cold worked, produced by rolling or drawing. T tempers are heat treated, used on the age hardening alloys.

The annealed tempers

O60, soft anneal. O61, annealed.

Fully softened material. It bends around tight radii without cracking, which is why busbar that gets formed is usually supplied annealed.

What it costs you at the machine: annealed copper is the gummiest condition there is. It smears rather than shears, burrs heavily and marks in the vise under pressure that would not touch half hard material. If your part is machined rather than formed, annealed is rarely the right order.

The cold worked tempers

H01, quarter hard. A compromise for parts that are both bent and machined. Some formability left, some stiffness gained.

H02, half hard. The working default for busbar stock and machined plate. Stiff enough to hold shape under clamping, machines noticeably better than annealed, still bends at a sensible radius. If you do not have a reason to choose otherwise, this is usually it.

H04, hard. Standard for drawn free-machining rod, which is why C14500 and C14700 turned parts are normally H04. Best surface finish of the three and the least formable. Bending hard temper copper at a tight radius cracks the outer fibre.

The trade across these three is consistent: more cold work means better machining and worse forming. Pick from whichever of those two your part actually does.

The heat treated tempers

These apply to the age hardening alloys: beryllium copper, chromium copper, chromium zirconium copper, zirconium copper and nickel beryllium copper.

TB00, solution heat treated. The soft condition. The alloy has been heated and quenched so the hardening elements are in solution but have not yet precipitated. This is the condition to machine in when you want an easier cut.

TD04, solution treated and cold worked to hard. Strength from cold work, before ageing.

TF00, precipitation hardened. Fully aged. Final strength, final hardness, final conductivity.

TH04, cold worked and precipitation hardened. The usual delivery condition for resistance welding electrode alloys, because it combines both strengthening routes.

The decision that matters on age hardening alloys

Machine soft then age, or machine in the hardened temper.

Machine at TB00, then age to TF00. Easier cutting, longer tool life, but the ageing treatment moves dimensions slightly. Predictable, but it is a movement, so tight features may need finishing afterwards.

Machine at TF00 or TH04. Dimensions are final off the machine. Slower cycle, harder on tooling, more cost.

Neither is universally right. Put the critical dimensions on the drawing and say which ones have to survive heat treatment, then let the shop plan the sequence. Dictating the route without telling the shop what matters is how parts come back correct on paper and wrong in the assembly.

Beryllium copper C17200 goes through this in detail for the alloy where it matters most.

Temper and conductivity

On pure copper this is a non-issue. Cold work changes conductivity by a fraction of a percent and no design notices.

On the age hardening alloys it is central. Nickel beryllium copper ranges from roughly 45 to 60 percent IACS depending on temper, which is a wide enough band that quoting the grade without the temper does not specify a conductor at all. Chromium copper reaches its useful 80 percent IACS only after ageing.

If your part has an electrical requirement and an age hardening alloy, the temper is part of the electrical specification. Write both.

What to put on the drawing

For pure and free-machining coppers, one line:

UNS C11000, ASTM B187, temper H02

For age hardening alloys, two pieces of information:

UNS C18200, RWMA Class 2,
supply TB00, age harden to TH04 after machining.
Dimensions marked * are final after heat treatment.

That second version tells the shop what it needs: what to buy, what the finished condition is, and which dimensions the heat treatment is not allowed to disturb.

Common mistakes

Specifying annealed because it sounds safe. It is the worst machining condition and it marks easily. Choose it only if the part is formed.

Leaving temper off a bent part. Bend radius depends on temper. A drawing that gives a tight radius and no temper is asking for cracked parts or a phone call.

Ordering hard temper and then asking for a bend. Hard copper cracks. Either the temper or the radius has to give.

Quoting an age hardening alloy without a temper. You have not specified the strength or the conductivity, which are the only two reasons to use those alloys.

The full list of grades with their usual tempers is in the copper grade reference, and the RFQ builder will write the callout for you.

Frequently asked questions

Keep reading

• C18150 vs C18200: Which Chromium Copper to Put on the Drawing
• C14700 Sulfur Copper: What It Gains Over C110 and Where It Stops