Non-Ferrous Metals
Non-ferrous metals (no iron) include aluminum, copper, brass, bronze, and magnesium. They are generally soft, conduct heat well, and machine at high speeds — but they have their own quirks, especially built-up edge and chip control.
Aluminum
Aluminum is the most machined non-ferrous metal. It is soft (HB 70–150), conducts heat well, and cuts at high speeds. But it is gummy and can weld to the cutting edge (built-up edge) if the tool is not sharp or the speed is too low.
Common aluminum grades
| Alloy | Condition | Properties | Machinability |
|---|---|---|---|
| 6061 | T6 | General purpose, medium strength | Good — the "default" aluminum |
| 7075 | T6 | High strength, aerospace | Good — slightly gummy |
| 2024 | T3/T4 | High strength, aerospace | Fair — more chip control needed |
| A380 / ADC12 | As cast | High silicon, die casting | Abrasive — use polished PCD or carbide |
| 1100 / 3003 | Soft | Pure / low alloy, very ductile | Gummy — long chips, needs high speed |
Machining aluminum — the rules
- Run fast: Vc = 300–600 m/min with polished carbide or PCD. The faster you go, the cleaner the cut — low speed causes built-up edge.
- Sharp, polished tool: use polished 2–3 flute end mills with high helix (35–45°). A rough or coated tool (TiN) encourages aluminum to weld to it.
- Generous chip clearance: 2–3 flutes (not 4–6) so chips don't pack in the flutes.
- Coolant: flood coolant or air blast. Air blast works well for chips; flood coolant helps with finish and built-up edge.
- Don't run too slow: the #1 aluminum machining mistake is running at steel-like speeds. At low RPM, the edge rubs, aluminum welds to the tool, and you get a poor finish with a built-up edge.
Worked example: 12 mm carbide end mill in 6061-T6. Vc = 400 m/min, fz = 0.05 mm/tooth, 3 flutes. RPM = 400×1000/(π×12) = 10,610 RPM. Feed = 0.05 × 3 × 10,610 = 1,592 mm/min. Most small VMCs top out at 8,000–12,000 RPM — right in the sweet spot for aluminum.
Copper and Copper Alloys
| Material | Properties | Machining notes |
|---|---|---|
| Pure copper (C110) | Very soft, conductive, ductile | Gummy — needs sharp tools, high speed, chip breaker |
| Brass (C360 free-cutting) | Copper + zinc + lead | Excellent — machines almost like 1215 steel, chips break free |
| Bronze (C932 bearing) | Copper + tin | Abrasive, slower speeds |
Brass is the best non-ferrous: free-cutting brass (C360) has lead added that acts as an internal chip breaker. It machines beautifully at high speeds with no built-up edge. If you get to choose the material, C360 is a dream.
Magnesium
Magnesium is the lightest structural metal (2/3 the density of aluminum). It machines extremely fast — like cutting balsa wood. But it has one critical safety issue: magnesium chips are flammable. Fine magnesium swarf can ignite and burn with an intense white flame. Never machine magnesium with water-based coolant — use dry cutting or special magnesium oil. Have a Class D fire extinguisher nearby.
Magnesium fire safety: never use water on a magnesium fire — it makes it burn hotter. Keep the chips dry, don't accumulate fine swarf, and know where your Class D extinguisher is.