CU · copper alloy
Cartridge Brass C26000 (70/30)
The 70/30 brass: excellent cold-forming and good machining, though without the lead it does not break a chip as cleanly as C360.
Quoting this material
- Typical lead time
- 7–14 working days
- Condition
- Annealed (soft) through to hard cold worked
- Achievable finish
- Ra 0.8 µm typical · Ra 0.2 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
The 70/30 brass: excellent cold-forming and good machining, though without the lead it does not break a chip as cleanly as C360.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 300–450 | MPa |
| Yield strength (0.2%) | 95–400 | MPa |
| Elongation | 50 (annealed) | % |
| Hardness | 110 | HV |
| Thermal conductivity | 120 | W/m·K |
| Modulus of elasticity | 110 | GPa |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
Annealed (soft) through to hard cold worked
Heat treatment
Not heat hardenable; it is a cold-working alloy, and it takes a lot of cold work before it needs annealing. Stress-relief annealing avoids season cracking in ammonia-bearing environments.
Achievable surface finish
Ra 0.8 µm
Ra 0.2 µm
Takes a very bright finish and polishes or plates well - the traditional reason it is used for visible hardware.
Tooling and cutting parameters
Cutting speed
- 150–300 m/min (carbide)
Feed
- 0.10–0.30 mm/rev turning · 0.08–0.20 mm/tooth milling
Tooling
- Uncoated carbide, high positive rake
Coolant
- Mist or flood
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Formed and drawn components
- Radiator and heat exchanger parts
- Plumbing hardware (lead-free grades)
- Electrical stampings and contacts
- Decorative architectural hardware
DFM notes for this grade
- Stress-corrosion cracking in an ammonia or amine environment is the classic failure: a cold-worked and machined part needs a stress relief if it will see those chemicals
- It is a lead-free alternative to C360 where a potable-water or restricted-material specification applies, at some cost in chip control
- The formability is the reason to use it - if the part is only machined, C360 or a lead-free free-cutting brass machines better
Questions buyers ask
- What does “season cracking” mean?
- Stress-corrosion cracking of cold-worked brass in an ammonia-bearing environment - historically brass cartridge cases cracking in storage in stables. The lesson applies today: a heavily cold-worked and machined brass part in ammonia or amine service needs a stress-relief anneal.
- Is C260 a drop-in for C360?
- Mechanically similar, but it machines less cleanly because it has no lead to break the chip. On a high-volume turned part the cycle time difference is real; on a part that is formed and then lightly machined, C260 is often the better material.
Grades we would quote instead
C36000 Free-Cutting Brass
10/10The reference point for the whole scale: free-cutting brass is 100% machinability in every published table and a 10 here.
C11000 ETP Copper
6/10Pure copper: gummy, prone to built-up edge and famous for long stringy chips.
C51000 Phosphor Bronze
6/10The spring bronze: good machinability with enough tin to give real strength and fatigue resistance.