Copper & Brass
Copper alloys are niche but critical — electrical connectors need conductivity, valve stems need beryllium copper's strength. The surprise for most people: brass is the easiest metal to machine, period. This page covers when to use which copper alloy.
Which Copper Alloy?
| Your Situation | Use This | Why |
|---|---|---|
| High-volume machined parts, fittings, valves | C36000 brass | Best machinability of any metal. 100% machinability rating. Cuts like butter. |
| Electrical connectors, bus bars | C11000 copper | Highest conductivity (101% IACS). But gummy to machine. |
| Need spring properties + conductivity | C17200 beryllium copper | BeCu can reach HRC 40 with conductivity. Valve seats, relay contacts, spring contacts. |
| Decorative / architectural hardware | C26000 (cartridge brass) | Good formability + gold-like appearance. Doorknobs, hinges. |
| Marine hardware | C46400 naval brass | Good corrosion resistance. Propeller shafts, marine fittings. |
Alloy Data at a Glance
| Property | C36000 Brass | C11000 Copper | C17200 BeCu |
|---|---|---|---|
| Type | Free-machining brass | ETP copper | Beryllium copper |
| Tensile (MPa) | 360 | 220 | 1200 (aged) |
| Yield (MPa) | 250 | 70 | 1100 (aged) |
| Density (g/cm³) | 8.50 | 8.96 | 8.25 |
| Conductivity (%IACS) | 26% | 101% | 20–30% (aged) |
| Machinability | 100% (best) | 20% (gummy) | 50% (before age) |
| Hardness | 78 HB | 45 HB | 38 HRC (aged) |
| Relative cost | 1.0x | 1.2–1.5x | 5–8x |
C36000 Brass — The Machining Dream
If you need to machine thousands of parts fast, C36000 brass is your material. It has the highest machinability rating of any metal (100% on the scale where free-machining steel is ~70%). Chip breaking is excellent, tool life is measured in thousands of parts, and surface finish is naturally smooth.
The lead content (2.5–3.5%) creates the free-machining characteristics. This also means it cannot be welded or used in potable water systems.
Beryllium copper warning
C17200 contains beryllium (1.8–2.0%). Machining produces fine dust that is toxic if inhaled. Most machine shops handle it with standard coolant and chip collection, but if you're machining large quantities, ensure proper ventilation. Do NOT dry machine beryllium copper.
Common Mistakes
| Mistake | What happens | Correct approach |
|---|---|---|
| Using C11000 for machined fittings | Terrible machinability, gummy chips, tool wear is 5x brass | For machined parts use C36000 brass |
| Using C36000 for electrical bus bars | Only 26% IACS conductivity — huge resistance | Use C11000 for electrical applications |
| Not age-hardening C17200 | Only 50% of its potential strength | Machine in solution-treated state, then age at 320°C for 2-3 hours |
| High cutting speed on brass | Buildup on tool, poor finish | Brass needs moderate speed (100-200 m/min) with high feed |