Which Copper Stock Form Your Part Should Be Cut From
September 26, 2026
Two things about a copper part are decided by the stock it comes from, before any cutting happens: what it costs in metal, and how much it moves after machining. The stock form is worth a line in the RFQ.
The forms
Plate and sheet. Rolled flat product. C11000 and C10100 in ASTM B152. Standard for busbar blanks, heat sink bases, cold plates and any part that is wide and flat. Carries rolling stress, so a part that has a lot of material removed from one side can bow. Wide thickness range, widely stocked in C11000.
Flat bar and busbar stock. Rolled or drawn rectangular section, ASTM B187 for C11000 and C10100. The natural form for busbar, often to a size that needs little machining on the faces. Available in H02 half hard as standard.
Round bar and rod. Drawn or extruded round section. ASTM B187 for pure coppers, ASTM B301 for free-machining grades. Turned parts start here. Free-machining rod in H04 is straight, has a good surface and cuts cleanly, which is why C14500 turned parts are so much cheaper than the same part in C11000 from plate.
Tube and pipe. ASTM B75 tube, B42 pipe, usually C12200 for brazed and plumbing work. Rarely machined beyond ends and holes.
Shapes and extrusions. Custom profiles for volume busbar. Mill lead times and minimums apply.
How the form changes the quote
Starting weight. A turned part from round bar wastes less than the same part sawn from plate. A flat part from bar stock close to finished size wastes less than one cut from thick plate. The shop pays for all of it and so do you. See how the copper price lands inside your quote.
Stress and movement. Rolled plate carries internal stress. Remove a lot of material from one face and the part moves. Drawn rod is more predictable. On flat parts with tight flatness, the form and the operation sequence decide whether the part stays flat. See copper machining tolerances.
Availability. C11000 plate and bar in common sizes are everywhere. C10100 in a specific thickness, or C14500 rod in an unusual diameter, may not be. The stock lead time is often the long pole. See copper lead times.
Temper. Plate and bar come H02 or annealed. Free-machining rod comes H04. If you need a different temper, it is a special order or a heat treatment.
What to put in the RFQ
Usually nothing beyond the material callout with the right ASTM specification, and the shop will choose the form. Write it when it matters:
- Grain direction on a part where bending or fatigue depends on it
- “From plate” or “from bar” when you have a reason, for example matching a previous batch
- A note that the part must stay flat to a tolerance, so the shop plans the form and sequence
The full callout with the ASTM specification per form is in how to specify copper on a drawing, and each grade’s specifications by form are on the copper grade reference.
Frequently asked questions
Does the stock form change the ASTM specification?
Yes. The same alloy is covered by different standards for plate, bar, rod and tube. C11000 plate is ASTM B152 and C11000 bar is ASTM B187. Name the standard for the form you are buying.
Why does a shop ask what stock the part comes from?
Because it sets the starting weight, the drop, the internal stress and often the lead time. A part nested from plate and the same part cut from bar can differ meaningfully in cost and in how much they move after machining.
Is drawn rod better than rolled bar for turned parts?
Drawn free-machining rod in H04 temper is the standard for turned parts because it is straight, has a good surface and cuts cleanly. Rolled bar suits milled parts and busbar. The shop will usually choose correctly if it knows the part.
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