The Copper Drawing Mistakes Shops See Every Week
September 25, 2026
These are the gaps that turn up in copper RFQs over and over. None of them are the buyer being careless. They are things that do not matter in aluminum and matter a great deal in copper, so nobody learned to write them down.
1. The word “copper” instead of a grade
What it costs. C11000 and C14500 differ by roughly four times in machinability. Quoting one and supplying the other is a margin event in either direction.
The fix. A full callout: material name, UNS number, ASTM specification for the product form, temper. Send the customer how to specify copper on a drawing and the problem stops recurring.
2. No temper
What it costs. Temper decides bend radius, machining behaviour and, on age hardening alloys, conductivity. A tight bend radius with no temper means either cracked parts or a phone call.
The fix. ASTM B601 code alongside the grade. H02 for most machined plate and busbar, H04 for drawn free-machining rod.
3. “Deburred” with no dimension
What it costs. The single largest source of scatter between quotes for the same copper part. One shop prices a 0.3 mm edge break, another prices hand inspection of every edge.
The fix. “Break all edges 0.2 to 0.4 mm”, plus named exceptions where a stricter condition is genuinely required.
4. A blanket surface finish
What it costs. Ra 0.8 on the whole part when one face needs it adds a finishing pass to every surface. On copper, where smearing rather than roughness is the usual failure, it also chases the wrong problem.
The fix. Ra values per face, with the function of each face named: contact, sealing, plated, cosmetic. Everything else as machined.
5. An incomplete plating spec
What it costs. Plating is an outside process with a minimum charge, a queue and its own inspection. “Tin plated” leaves thickness, area, masking and pre or post plate dimensions all open, and every shop assumes differently.
The fix. Finish and underlayer, thickness for contact and non-contact areas, plated and masked areas marked on the drawing, and whether dimensions apply before or after plating.
6. Tolerances applied everywhere
What it costs. Tight general tolerances on a soft metal that moves with heat and clamping pressure add inspection and finishing time to features that never needed it, and they hide the two or three dimensions that actually matter.
The fix. A sensible general block, with specific tolerances on the features that mate, locate or seal. The realistic bands are in copper machining tolerances.
7. No clamping guidance
What it costs. Copper marks under pressure that would not touch steel. A jaw print on a contact face is a real defect, and finding out at first article means rework on the whole batch.
The fix. A note naming which faces may carry clamping marks and which may not, and ideally a sacrificial area to grip.
8. Cross holes with no burr instruction
What it costs. The burr inside a cross hole intersection is the hardest one on any copper part to reach. It may need a specific tool, a changed operation order or a secondary process, and none of that is in a default price.
The fix. State explicitly whether internal intersections must be clean, and how it will be judged.
How to raise these without sounding difficult
Ask three questions rather than eight. Grade, edge condition and plating scope decide most of the price, and a short specific list reads as competence.
A useful framing: “I can quote this two ways. As drawn in C11000, or in C14500 if your conductivity requirement has headroom, which would be meaningfully cheaper. Which do you want?” That is a question a buyer enjoys receiving.
What to send them
Rather than writing the explanation again, point at it:
- How to specify copper on a drawing for the material callout
- The copper grade reference for the grade decision
- The RFQ builder, which writes the specification lines from a few answers
Buyers generally want to get this right. They have not been given the vocabulary, and a shop that hands it over is the shop they come back to.
The pricing side
How to price a copper RFQ covers what to do with the answers once you have them, including how to carry deburring and metal price exposure without eating them.
Frequently asked questions
Why do quotes for the same copper part vary so much between shops?
Usually the edge condition. A drawing that says burr free without a dimension is priced as a light edge break by one shop and as hand inspection of every edge by another. That single line can be a large fraction of the part cost.
Is it worth going back to the customer before quoting?
Yes on grade, edge condition and plating scope. Those three decide most of the price. A short list of specific questions reads as competence and usually shortens the whole cycle.
Can I just quote my assumptions and move on?
You can, provided the assumptions are written on the quote. Unstated assumptions become disputes at first article, and the shop usually loses those.
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