Aerospace Aluminum High-Speed Milling: Sandvik CoroMill and Korloy End Mill Selection Guide

Aerospace aluminum alloys, including 7075-T6, 6061-T6, and 2024-T3, represent one of the most challenging material groups in modern CNC machining. Classified under ISO Group N (non-ferrous metals), these materials exhibit high thermal conductivity, low hardness, and a strong tendency toward built-up edge (BUE) formation when machined at suboptimal parameters. Selecting the correct milling tool is not merely a matter of convenience; it directly determines surface integrity, dimensional accuracy, tool life, and overall productivity.

In this comprehensive guide, we compare two industry-leading solutions for aerospace aluminum high-speed milling: Sandvik CoroMill platforms and Korloy KFMA/KMG series. We examine cutter geometries, carbide grades, coating strategies, and provide detailed cutting parameter recommendations for roughing, semi-finishing, and finishing operations.

Why Aerospace Aluminum Demands Purpose-Built Tooling

Aluminum alloys used in aerospace applications possess distinct metallurgical characteristics that influence cutting performance:

• High thermal conductivity (121–209 W/m·K): Heat dissipates rapidly into the workpiece rather than the chip, requiring aggressive cutting speeds to concentrate thermal energy at the shear zone.
• Low hardness (HRB 40–90): While this reduces abrasive wear, it promotes adhesion between the chip and rake face, leading to built-up edge and poor surface finish.
• Silicon content variations: 7xxx series (Zn-dominated) behave differently from 2xxx series (Cu-dominated) or 6xxx series (Mg-Si). Silicon-rich alloys (e.g., 4047 cladding) increase abrasiveness.
• Thin-wall structures: Aerospace components often feature webs and ribs as thin as 0.8 mm, requiring low cutting forces and excellent chip evacuation.

Consequently, tool selection must prioritize high positive rake angles, sharp cutting edges, polished flutes, and large chip pockets to prevent re-cutting and ensure efficient chip evacuation.

Sandvik CoroMill Platform for ISO N Materials

Sandvik Coromant offers a mature ecosystem of indexable and solid carbide milling tools specifically optimized for non-ferrous materials. Two product families dominate aerospace aluminum machining: the CoroMill 390 indexable shoulder milling system and the CoroMill Plura solid carbide end mill range.

CoroMill 390 Long-Edge Milling Cutter

The CoroMill 390 is a versatile shoulder milling cutter available in diameters from 16 mm to 160 mm. For aluminum applications, Sandvik provides specialized insert geometries and grades:

• Insert geometry: -L (light cutting) and -AL (aluminum-optimized) chipbreakers feature highly positive rake angles (15°–20°) and sharp edges to minimize cutting forces.
• Carbide grade: H13A is an uncoated fine-grain cemented carbide (WC-Co) grade specifically developed for ISO N materials. Its high cobalt content (typically 10–12%) provides excellent edge toughness, while the absence of coating eliminates any risk of aluminum adhesion to the tool surface.
• Polished rake face: Mirror-polished insert surfaces reduce friction coefficient and prevent material buildup.

CoroMill Plura Solid Carbide End Mills

For intricate 3D profiling, pocketing, and high-speed finishing of aerospace components, the CoroMill Plura HFS (High Feed/Speed) range provides optimized flute designs:

• Flute count: 2-flute and 3-flute designs are standard for aluminum. Two-flute cutters offer maximum chip space, while three-flute variants balance productivity and finish quality.
• Helix angle: 30°–45° helix angles smooth cutting forces and reduce vibration in thin-wall applications.
• Edge preparation: Sharp edges with minimal hone (5–10 μm) reduce ploughing forces and improve surface finish.
• Coating: Most Plura aluminum tools remain uncoated or feature a minimal PVD TiB₂ coating for extreme cases. The base material is typically micro-grain carbide (0.5–0.8 μm grain size).

Korloy High-Speed Aluminum Milling Solutions

Korloy has established a strong presence in the aerospace sector with the KFMA indexable high-feed milling series and the KMG solid carbide end mill family. These platforms emphasize aggressive metal removal rates and stable machining dynamics.

KFMA Series Indexable Milling Cutter

The KFMA line is designed for high-efficiency face and shoulder milling in non-ferrous materials. Key technical characteristics include:

• Double-sided insert design: KFMA inserts offer four cutting edges, delivering low cost per edge without compromising edge sharpness.
• High-positive geometry: 18°–22° axial rake angles reduce cutting forces by approximately 15–20% compared to neutral geometries, critical for thin-wall aerospace structures.
• Grade recommendation: PCD (Polycrystalline Diamond) tipped inserts are available for KFMA holders when machining high-silicon aluminum or when extended tool life is required. For general aerospace alloys, uncoated fine-grain carbide (equivalent to K10–K20 classification) is recommended.
• Chip evacuation: Large flute spacing and through-coolant capability (when equipped) enhance chip flow in deep cavity operations.

KMG Series Solid Carbide End Mills

Korloy’s KMG end mills are engineered for high-speed finishing and semi-roughing of aluminum components:

• Flute profile: Deep, polished flute gullets with a large core diameter provide rigidity while maintaining efficient chip evacuation.
• Corner radius options: Standard offerings include sharp corner, 0.5 mm, 1.0 mm, and 2.0 mm radii, accommodating various aerospace feature requirements.
• Coating: KMG tools for aluminum typically feature a diamond-like carbon (DLC) or minimal TiAlN coating variant optimized for low-friction cutting. However, uncoated versions remain the first choice for pure aluminum and low-silicon alloys.
• Runout tolerance: ≤ 5 μm on the cutting edge ensures consistent surface finish in high-speed applications (spindle speeds > 20,000 rpm).

Side-by-Side Technical Comparison

The following table provides a direct comparison of Sandvik and Korloy platforms across critical technical dimensions:

Application-Specific Selection Guidelines

Beyond raw parameters, successful aerospace aluminum machining depends on matching the tool to the specific manufacturing scenario.

Wing Rib and Spar Machining

These components feature long, thin walls (1–3 mm thickness) and extensive pocketing. Sandvik CoroMill 390 with -AL geometry is the preferred choice due to its low cutting force profile and excellent wall accuracy. For 3D curved surfaces, CoroMill Plura 3-flute cutters at ae = 0.05 × Dc and Vc = 2,000 m/min deliver superior surface finishes (Ra 0.4–0.8 μm).

Structural Frame Components

Heavier sections with thicker stock removal favor the Korloy KFMA platform. Its double-sided inserts and aggressive feed capabilities (fz up to 0.22 mm) maximize material removal rates. PCD-tipped KFMA inserts extend tool life by 300–500% when machining silicon-enriched cladding layers common on 7075 aerospace plate.

High-Speed Finishing of Mold Cavities and Dies

For mold applications requiring mirror-like finishes, uncoated solid carbide end mills from either manufacturer are suitable. Key is to maintain high spindle speeds (18,000–30,000 rpm) with minimal radial engagement to generate thin, manageable chips. DLC-coated KMG tools offer a slight advantage in lubricity when cutting 6xxx series alloys with higher magnesium content.

Coolant and Machine Tool Considerations

Aerospace aluminum machining benefits significantly from optimized coolant delivery:

• Volume flow rate: Minimum 10–15 L/min per cutting edge for flood coolant; higher for through-spindle systems.
• Concentration: 5–8% soluble oil emulsion or synthetic coolant with EP additives.
• Spindle requirements: High-speed spindles (HSK 63A or HSK 100A) with ceramic bearings and active cooling are essential for sustained operation above 15,000 rpm.
• Machine rigidity: Despite low cutting forces, high-speed milling generates dynamic vibrations. Machines with polymer concrete bases or active damping systems produce measurably better surface finishes.

Conclusion

Both Sandvik and Korloy offer technically mature solutions for aerospace aluminum high-speed milling, but their strengths align with different application profiles. Sandvik CoroMill 390 and Plura excel in precision shoulder milling, thin-wall machining, and complex 3D contouring where cutting force minimization and surface finish are paramount. Korloy KFMA and KMG platforms deliver superior economy and productivity in general roughing, face milling, and high-feed applications where material removal rate takes priority.

Ultimately, the optimal selection depends on the specific alloy grade, component geometry, machine tool capability, and production volume. By leveraging the cutting parameters and technical comparisons presented in this guide, manufacturing engineers can make data-driven tooling decisions that reduce cycle time, extend tool life, and maintain the stringent quality standards demanded by the aerospace industry.