In the competitive world of CNC machining and mold manufacturing, the roughing and semi-finishing stages on pre-hardened materials like P20, 718H, and NAK80 demand tools that can withstand high cutting forces while delivering superior surface quality. These materials, widely used in plastic injection molds and die-casting dies, are typically supplied in a pre-hardened state (HRC 30–43) to eliminate the need for post-machining heat treatment-11. This pre-hardened condition, however, places significant demands on cutting tools—requiring a balance of wear resistance, toughness, and vibration damping. The GREWIN GRS Mold-Specific End Mill is engineered specifically for this application window. Designed for HRC 40°–50°, the GRS Mold-Specific End Mill combines a premium GW12 carbide substrate (0.4μm grain size, HRA 92.2) with an advanced CA02 CrAlN coating (3200 HV, 1100°C oxidation temperature), delivering exceptional wear resistance, anti-vibration performance, and surface finish quality in slot milling and contouring operations on P20, 718H, and NAK80.
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The Substrate and Coating Technology Behind GRS Mold-Specific End Mill
The performance of the GREWIN GRS Mold-Specific End Mill is built upon two critical elements: a premium carbide substrate and a coating specifically developed for pre-hardened steel machining applications.
GW12 Substrate: High Cobalt, Fine Grain, Exceptional Bending Strength
The GW12 substrate used in the GRS Mold-Specific End Mill represents a carefully balanced carbide grade optimized for roughing and semi-finishing of pre-hardened mold steels. With a cobalt content of 12%, a fine grain size of 0.4 μm, and a hardness of HRA 92.2, the GW12 substrate delivers an excellent combination of toughness and wear resistance. The bending strength of ≥4000 N/mm² ensures the tool can withstand the high cutting forces typical of slot milling and heavy roughing operations without chipping or catastrophic failure. This substrate formulation makes the GREWIN GRS Mold-Specific End Mill especially effective for P20, 718H, and NAK80—materials that combine moderate hardness with challenging chip formation characteristics-1-5.
CA02 CrAlN Coating: Heat Resistance and Low Friction
The CA02 coating on the GREWIN GRS Mold-Specific End Mill is a Chromium Aluminum Nitride (CrAlN) PVD coating engineered for demanding machining conditions. The coating’s key properties—3200 HV hardness, 1100°C oxidation temperature, and 0.35 coefficient of friction—deliver three core benefits:
- Extended Wear Resistance: High hardness protects the cutting edge from abrasive wear, delivering longer tool life in production runs.
- Thermal Stability: The elevated oxidation temperature allows sustained performance at higher cutting speeds, enabling increased productivity.
- Reduced Friction: Low friction minimizes heat generation and improves workpiece surface finish.
CrAlN-coated carbide end mills are particularly recognized as suitable for dry, high-speed machining applications, offering better resistance to cracking and oxidization than TiAlN coatings.
Optimized Helix Angles for Specific Geometries
The GREWIN GRS Mold-Specific End Mill series features differentiated helix angle design based on tool geometry:
- Flat End Mills: 45° Helix Angle — optimized for slot milling and general roughing, providing a balance of cutting force reduction and edge strength.
- Ball-Nose End Mills: 35° Helix Angle — optimized for contouring and finishing on curved surfaces, offering stability in radial engagement.
Industry best practices confirm that larger helix angles (35°–45°) enable smoother chip evacuation and reduce cutting heat accumulation, particularly beneficial when machining pre-hardened steels like NAK80 and P20-2-10. The GRS series applies these principles with geometry-specific optimizations.
Real-World Performance: GRS Slot Milling on P20
To validate the performance of the GREWIN GRS Mold-Specific End Mill, comprehensive slot milling tests were conducted on P20 steel at 35 HRC using a vertical machining center.
Test Parameters and Setup
| Parameter | Value |
|---|---|
| Tool Model | D12.03075L*4F-RS |
| Workpiece Material | P20 (35 HRC) |
| Machining Type | Slot Milling |
| Cutting Speed | 150 m/min |
| Feed per Tooth | 0.06 mm/z |
| Depth of Cut | 6 mm |
| Cooling Method | Air Cooling |
Anti-Vibration Performance and Surface Quality
Under identical conditions, the GREWIN GRS Mold-Specific End Mill demonstrated superior anti-vibration performance compared to competitor products. The optimized cutting edge design, combined with the 45° helix angle and strengthened edge geometry, effectively suppressed chatter during slot milling—a common challenge when machining pre-hardened steels-4-12.
The resulting workpiece surface quality was clearly superior to the competitor’s product. P20 mold steels are widely used in mid-volume production of plastic injection molds and die-casting dies, and surface finish directly impacts final component quality-11.
Real-World Performance: RS Ball-Nose End Mill on NAK80
The RS Ball-Nose End Mill (R3.01250L-RS, 2-flute, Φ6.0mm), part of the GREWIN GRS series, was tested on NAK80 at 40 HRC using a Makino F3 machining center.
Test Parameters and Setup
| Parameter | Value |
|---|---|
| Tool Model | R3.01250L-RS (Φ6.0mm ball-nose) |
| Workpiece Material | NAK80 (40 HRC) |
| Spindle Speed | 10600 r/min (200 m/min) |
| Скорость подачи | 2120 mm/min (0.2 mm/r) |
| Axial Depth of Cut (ap) | 0.2 mm |
| Radial Depth of Cut (ae) | 0.3 mm |
| Cutting Method | Unidirectional Linear Zig Milling |
| Cooling Method | Air/Water/Oil (All compatible) |
| Machine | Makino F3 |
| Tool Overhang | 20 mm |
| Measurement Equipment | TM2000 Roughness Tester |
Surface Finish and Tool Wear Comparison
The RS Ball-Nose End Mill delivered a clear, distinct cutting pattern with low roughness values and high surface quality. Under identical test conditions, the GREWIN tool exhibited slower flank wear progression with increasing cutting length compared to competitor products.
Key comparison outcomes:
- ✅ GREWIN RS Ball-Nose End Mill: Superior surface finish quality; tool wear grows slowly with cutting length.
- ❌ Competitor Tool: Inferior surface finish; wear accelerates rapidly with cutting length.
NAK80 is a premium-grade, pre-hardened steel known for its superior machinability and mirror-like finish capability, making it suitable for high-gloss optical and cosmetic molds-1-5. The RS ball-nose end mill is specifically designed to achieve the high surface quality required for these applications.
Application Summary and Selection Guide
The GREWIN GRS Mold-Specific End Mill series delivers reliable, high-performance tooling for roughing and semi-finishing on pre-hardened mold steels.
GRS Flat End Mill Summary
- Primary Application: Slot milling, general roughing
- Key Advantage: Excellent anti-vibration performance, superior surface quality
- Target Materials: P20, 718H, pre-hardened steels
H3: RS Ball-Nose End Mill Summary
- Primary Application: High-quality finishing on curved surfaces
- Key Advantage: Low wear progression, superior surface finish, extended tool life
- Target Materials: NAK80 (40 HRC), similar pre-hardened steels
Both tools have been validated through real-world cutting tests, including documented cutting parameters, surface samples, and wear curve comparisons against competitor products.
Competitive Positioning
The GREWIN GRS Mold-Specific End Mill series offers a direct alternative to:
- Mitsubishi MHS50 — comparable anti-vibration slot milling performance
- Walter MC380 — similar high-surface-finish capability
- Sandvik CoroMill 2P340 — equivalent wear resistance and cutting stability
With competitive pricing and ready stock availability, the GRS series delivers proven performance at a superior total cost value.
Заключение
The GREWIN GRS Mold-Specific End Mill series delivers a comprehensive, application-matched solution for roughing and semi-finishing on pre-hardened mold steels. By combining a robust GW12 carbide substrate (0.4μm grain, HRA 92.2) with a durable and heat-resistant CA02 CrAlN coating (3200 HV, 1100°C), the GRS series provides exceptional anti-vibration performance, superior surface finish, and extended tool life in slot milling and contouring applications on P20, 718H, and NAK80. Real-world testing confirms that GRS not only delivers superior surface quality but also exhibits slower wear progression than competitor products. For mold and die manufacturers working with pre-hardened steels in the HRC 40–50 range, the GREWIN GRS Mold-Specific End Mill represents a cost-effective solution engineered for the demands of production environments.
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About Grewin Tools
Grewin Tools is a leading manufacturer and supplier of precision CNC tooling and metalworking solutions. With over 20 years of experience and a strong R&D center, we offer a comprehensive range of carbide products including GRS Mold-Specific End Mills, solid carbide end mills, CNC inserts, and tool holding systems.
Contact Us Today
Ready to optimize your roughing and semi-finishing operations with the GREWIN GRS Mold-Specific End Mill series? Contact Grewin Tools for a catalog, technical support, or to request a quote.
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