Engineering · Machining guide
How to machine MIC-6 cast aluminum plate.
MIC-6 is poured cast aluminum plate, slow-cooled and double-sided machined at the mill — internal stresses are essentially zero. Machinability is similar to 6061 (close to 90/100), but the cast structure brings two unique considerations: occasional porosity and lower yield strength. The use case is dimensional stability, not load-bearing.
01 · Why MIC-6 vs 6061
Stability over strength.
6061 plate normally ships as T651 — solution-treated, quenched and stress-relieved by stretching — but the stretch only reduces the rolling and quench stresses. Heavily machined parts, especially thin or asymmetric ones, can still move as the remaining stress is released.
MIC-6 is fundamentally different. The molten aluminum is poured into a mold, slow-cooled in place, stress-relieved, and both faces are precision-milled at the mill. As a cast and stress-relieved product it has no rolling stresses, and internal stress is essentially zero from the casting process forward. The part stays where you put it. The trade-off: lower strength (~165 MPa UTS vs ~310 for 6061-T6) and slightly more porosity due to the cast structure. For optical mounts, metrology fixtures, and vacuum hardware, that’s a deal you happily make.
See our MIC-6 vs ATP-5 vs 6061 comparison for the broader trade-offs.
02 · Cutting parameters
Treat it like 6061.
| Operation | Tool | SFM | IPT / IPR |
|---|---|---|---|
| Roughing mill | Uncoated carbide 3FL | 1000–1800 | 0.005–0.012 IPT |
| Finishing mill | Uncoated carbide 3FL | 1500–2200 | 0.003–0.008 IPT |
| Roughing turn | Uncoated carbide | 1000–2000 | 0.012–0.025 IPR |
| Finishing turn | Uncoated carbide | 1500–2500 | 0.005–0.012 IPR |
| Drilling | Solid carbide | 300–500 | 0.005–0.015 IPR |
| Tapping | HSS | 50–100 | — |
IPT (chip-load) values assume roughly ½–1″ end mills; scale down for smaller tools — see the chip-load chart.
03 · Practical notes
Porosity is the unique consideration.
- Tooling: uncoated polished carbide — same as 6061. Sharp edges with positive rake.
- Coolant: water-soluble flood, MQL, or dry. MIC-6 generates clean chips like 6061.
- Porosity: occasional small voids are inherent to cast plate. For optical, sealing, or vacuum-tight applications, plan around it — leave finish stock to clean up minor porosity, or specify ATP-5 (premium grade) for tighter porosity control.
- Don’t machine deeper than the spec sheet allows: some MIC-6 grades have only ~0.060″–0.125″ of as-cast surface that’s machined off at the mill. Going deeper than that exposes raw cast structure that may have more porosity.
- Anodize quality: generally good but not as clean as wrought 6061. For cosmetic-critical work, finish-machine to remove surface imperfections, then Type II anodize.
- Don’t use MIC-6 for load-bearing parts: 165 MPa UTS is half of 6061. Optical mounts, fixtures, plates — yes. Brackets carrying real load — no, use 6061 or 7075.
Keep exploring
Related tools & references
Stress-free precision cast plate properties.
MIC-6 vs ATP-5 vs 6061 trade-offs.
Run MIC-6 at 6061-class speeds and feeds.
Per-tooth chip loads for cast aluminum plate.
2.80 g/cc — fixture and tooling-plate weights.
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