How to Specify Copper on a Drawing So It Quotes Right
Updated September 26, 2026
A copper drawing that says “copper” has not specified anything. The word covers alloys whose conductivity runs from 22 to 101 percent IACS and whose machinability runs from 20 to 85 against free-cutting brass. Those are different materials doing different jobs, and the shop is the one left choosing between them.
Here is the callout that removes the ambiguity, in four parts.
1. Material name
Write it out in words. Not because the machine needs it, but because a human will read this drawing under time pressure, and “electrolytic tough pitch copper” catches an error that “C11000” alone does not.
2. UNS number
Five characters that fix the alloy exactly. Copper alloys run from C1xxxx to C7xxxx and machined work sits almost entirely in two blocks:
- C1xxxx coppers, at least 99.3 percent copper. This includes the pure grades, the free-machining grades and the age hardening grades.
- C3xxxx leaded brasses, where the machinability reference point sits.
The copper grade reference lists every grade that gets machined, with conductivity, machinability and what each one is for.
3. ASTM specification, for your product form
This is the part most drawings miss. The same alloy is covered by different standards depending on whether you are buying bar, sheet or tube, and the standard is what fixes the chemistry limits, the mechanical properties and the testing.
| Grade | Bar, rod and shapes | Sheet, strip and plate |
|---|---|---|
| C10100 oxygen free | ASTM B187 | ASTM B152 |
| C11000 ETP | ASTM B187 | ASTM B152 |
| C12200 DHP | confirm with supplier | ASTM B152, ASTM B75 for tube |
| C14500 tellurium | ASTM B301 | confirm with supplier |
| C14700 sulphur | ASTM B301 | confirm with supplier |
| C17200 beryllium | ASTM B196 | ASTM B194 |
| C36000 free-cutting brass | ASTM B16 | confirm with supplier |
For the chromium and zirconium coppers, the ASTM specification depends on form and supplier, and the RWMA class does more useful work on a drawing. See RWMA classes for copper welding electrodes.
Where we are not certain of a specification we say so rather than printing one that might be wrong. Our sourcing rules are on the editorial standards page.
4. Temper, per ASTM B601
Temper is a specification, not a detail. It changes strength, bend radius, how the material machines and, on the age hardening alloys, the conductivity itself.
The codes you will use in practice:
| Code | Meaning |
|---|---|
| O60, O61 | Annealed. Bends easily, machines gummily. |
| H01 | Quarter hard. |
| H02 | Half hard. The default for busbar and machined plate. |
| H04 | Hard. Standard for drawn free-machining rod. |
| TB00 | Solution treated, for machining before age hardening. |
| TF00 | Precipitation hardened. |
| TH04 | Cold worked and precipitation hardened. |
Copper temper codes explained covers what each one does to a part.
Putting it together
Electrolytic tough pitch copper,
UNS C11000,
ASTM B187 (bus bar, rod, bar and shapes),
temper H02That is a specification. A shop can buy against it, quote against it and be held to it.
The fifth line: substitution
Decide this deliberately and write it down.
“No substitution.” Use it when a substitution would break the part. Vacuum components, hydrogen brazed assemblies and anything with a certified conductivity requirement belong here.
“Substitution accepted if minimum 90 percent IACS is met.” Use it when you care about the property rather than the label. This is the line that saves the most money in copper, because it lets a shop offer C14500 in place of C11000 and cut the machining time several times over.
Silence is the worst option. It gets you either the expensive grade you did not need, or a substitution you were not told about.
What else belongs on a copper drawing
The material callout is necessary and not sufficient. Four more lines decide whether quotes are comparable:
- Edge condition as a dimension. “Break all edges 0.2 to 0.4 mm”, not the word deburred. See deburring copper parts.
- Surface finish per face, with what each face does: contact, sealing, plated, cosmetic.
- Plating spec with finish, thickness for contact and non-contact areas, plated and masked areas, and whether dimensions apply before or after plating.
- Inspection requirements, stated before the quote rather than after the shipment.
The RFQ builder writes all of these for you from a few answers, including the right UNS and ASTM lines for the grade you pick.
The one minute version
Write the material name, the UNS number, the ASTM specification for your form and the temper. Then decide out loud whether a substitution is allowed and on what condition. Everything else about a copper quote gets easier after that.
Frequently asked questions
Is writing C110 on the drawing enough?
It is most of the way there. Add the ASTM specification for your product form and the temper, because bar, rod, sheet and tube are different standards for the same alloy and temper changes strength, bend radius and machining behaviour.
What happens if I just write copper?
The shop buys whatever it can get. Copper covers alloys from 22 to 101 percent IACS and from 20 to 85 on the machinability scale, so the part you receive can perform nothing like the one you designed and still match the drawing.
Should I allow substitutions?
Only with a stated requirement. Write the conductivity, current or thermal figure next to the grade and mark substitution as acceptable if it is met. That lets a shop offer a cheaper alloy honestly instead of guessing.
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