Engineering · Machining guide
How to machine 6061-T6 aluminum.
6061-T6 is the easiest of the common aerospace alloys to machine — high SFM, fast feeds, low cutting forces, and great surface finish from a sharp polished-flute tool. The interesting machining problems aren’t about how to remove material; they’re about how to handle long stringy chips, prevent built-up edge, and keep dimensional stability through the cut.
01 · Tool selection
Polished flutes, sharp edges, no coating needed.
- Uncoated solid carbide with polished flutes
Polished flutes shed aluminum chips cleanly without built-up edge. Coatings (TiN, TiCN, AlTiN) actually hurt aluminum work — they create chip welding. Plain uncoated micro-grain carbide is the right answer.
- 3-flute end mills for general work
2 flutes for plunging and slot work; 3 flutes for general profiling (good chip clearance and balanced cutting); 4-flute for roughing where MRR matters more than chip evacuation.
- Sharp positive rake on inserts
Aluminum-specific insert geometry with extremely sharp edges and high positive rake. Designed for low cutting force and clean chip flow.
- PCD for high-volume production
Polycrystalline diamond inserts give 50–100× the tool life of carbide on aluminum at higher SFM. Pays back on production runs above ~500 parts.
02 · Cutting parameters
Fast — most modern machines hit RPM limits before the metal complains.
| Operation | Tool | SFM | IPT / IPR |
|---|---|---|---|
| Roughing turn | Uncoated carbide | 1000–2000 | 0.012–0.025 IPR |
| Finishing turn | Uncoated carbide | 1500–2500 | 0.005–0.012 IPR |
| Finishing turn | PCD | 3000–5000 | 0.005–0.010 IPR |
| End mill (rough) | Solid carbide 3FL | 800–1500 | 0.005–0.012 IPT |
| End mill (finish) | Solid carbide 3FL | 1200–2000 | 0.003–0.008 IPT |
| Drilling | Solid carbide | 300–500 | 0.005–0.015 IPR |
| Tapping | Spiral-flute HSS | 50–100 | — |
| Reaming | Solid carbide | 150–300 | 0.003–0.010 IPR |
IPT (chip-load) values assume roughly ½–1″ end mills; scale down for smaller tools — see the chip-load chart.
On many production parts, machine RPM caps the actual SFM you can run. A 1/4″ end mill at 1500 SFM works out to 22,900 RPM — beyond even an 18,000 RPM high-speed spindle (which caps it around 1,180 SFM), let alone a 12,000 RPM general-purpose mill (roughly 785 SFM).
03 · Coolant + practical notes
Flood, MQL, or dry — depends on the operation.
- Flood coolant: standard for most operations. 6061 doesn’t need EP additives; clean water-soluble emulsion is fine. Coolant flushes chips and prevents built-up edge.
- MQL or dry for fast surfacing: for high-RPM face-mill or shoulder-mill work, MQL (minimum quantity lubrication) gives equal life to flood without the chip-and-coolant cleanup. Pure dry milling works for short cycles but eventually the tool packs.
- Climb mill always: conventional milling re-cuts chips and creates burrs. Climb is universal in aluminum.
- Stress-relief on long parts: 6061-T6 wrought plate has internal stress that releases during machining. For long, thin parts (>12″ with thin walls), expect 0.005–0.020″ of warpage. For tight long-term stability, switch to MIC-6 cast plate.
- Anodize considerations: Type II for cosmetic and corrosion protection; Type III for wear surfaces. Plan dimensional growth (~100% of coating thickness adds to an OD — ≈50% per surface × 2). See anodize comparison.
- Common AMS: 4027 (sheet T6), 4117 (plate T651). See AMS spec cross-reference.
Keep exploring
Related tools & references
Mechanical properties, UNS, AMS specs, and machinability at a glance.
Convert these SFM and IPT figures into spindle RPM and feed rate.
Recommended chip load by tool diameter for aluminum.
6061 aluminum density for part weight and stock estimates.
When to step up from 6061-T6 to a higher-strength aluminum.
Need 6061-T6 aluminum parts machined?
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