With the continuous development of CNC precision machining technology, high-speed dry cutting has gradually become a prominent trend that combines efficiency with environmental sustainability. In this context, diamond milling cutters—particularly PCD tools and CVD diamond-coated milling cutters—demonstrate excellent wear resistance, high thermal conductivity, and superior surface finishing capabilities. These tools are widely recognized for their high value in machining graphite electrodes, carbon fiber composites, ceramics, and high-silicon aluminum alloys.
What Is a Diamond Milling Cutter?
Definition and Characteristics of Diamond Milling Cutters
Diamond milling cutters are superhard tools that use synthetic or natural diamond as the cutting edge material. They are designed for high-efficiency machining of hard and abrasive materials. With extreme hardness and outstanding wear resistance, these tools also feature a lower friction coefficient than conventional carbide cutters. In real-world applications, diamond tools significantly improve both tool life and surface finish.
Depending on machining needs, diamond milling cutters are applied extensively in CNC high-speed machining, dry cutting, and precision manufacturing. They are particularly suited for processing difficult materials like graphite, carbon fiber, ceramics, and high-silicon aluminum alloys. Their superior thermal conductivity enables stable performance in coolant-free environments, making them essential tools in modern high-end manufacturing.
Differences Between PCD and CVD Diamond Milling Cutters
The two primary types of diamond milling cutters in the market today are PCD diamond cutters and CVD diamond-coated cutters. Each has unique strengths and application scenarios.
PCD cutters are sintered from polycrystalline diamond and offer exceptional wear resistance and chip control. These tools are ideal for machining aluminum alloys, carbon fiber, and graphite materials where surface quality is critical. PCD cutters are mainly used for semi-finishing and finishing operations but are somewhat limited when it comes to extremely hard materials or intricate profiles.
CVD diamond-coated cutters are created by depositing an ultra-fine diamond film onto a carbide substrate via chemical vapor deposition. These tools are optimized for high-speed dry cutting of graphite and extended use on other highly abrasive materials. They are particularly suited for electrode fabrication and micro-precision machining.
Understanding the structural and performance differences helps engineers select the most suitable diamond milling cutter based on specific machining requirements, ensuring an optimal balance between efficiency and durability.
Primary Materials Suitable for Diamond Milling Cutters
Diamond milling cutters are especially valuable for materials that are challenging for traditional tools. Below are some common application materials:
- Graphite: Its porous structure and abrasiveness cause rapid wear in carbide tools. Diamond milling cutters for graphite significantly improve tool life and electrode machining precision.
- Carbon Fiber Composites (CFRP): These materials are prone to delamination. PCD tools enable dry machining while minimizing heat damage and burrs.
- High-Silicon Aluminum Alloys: Common in automotive and aerospace parts, their high silicon content accelerates tool wear. Diamond tools provide more stable performance.
- Ceramics and Glass: These brittle materials demand high cutting precision and minimal tool wear. CVD diamond milling cutters excel in these scenarios.
These characteristics make diamond milling cutters indispensable in modern CNC machining, especially in high-speed, dry-cutting environments that prioritize surface quality and extended tool life.
Basic Concepts of Dry Cutting and High-Speed Cutting
Advantages and Challenges of Dry Cutting
Dry cutting eliminates the use of coolant or lubricants during machining. As environmental regulations tighten and manufacturers seek cost-effective processes, dry cutting is gaining traction—especially when using diamond end mill cutters.
Advantages of dry cutting include:
- Lower cost and reduced complexity from eliminating coolants.
- Improved workplace cleanliness and environmental compliance.
- Reduced thermal distortion and cleaner part finishes.
Challenges include:
- Concentrated heat at the cutting zone.
- Accelerated tool wear if inadequate tool materials are used.
- Greater demands on machine tool rigidity and thermal stability.
Only tools with exceptional thermal conductivity and wear resistance—such as PCD and CVD diamond milling cutters—can meet the rigorous demands of dry machining.
Principles and Key Parameters of High-Speed Cutting
High-speed cutting involves machining at speeds significantly higher than conventional methods. It is enabled by high-precision CNC equipment and advanced tooling, and is widely used in aerospace, mold manufacturing, and electronics.
Key parameters include:
- Spindle speeds between 20,000–60,000 rpm.
- Elevated cutting speeds (Vc), especially for non-metallic materials.
- Shallow depth of cut and high feed rates.
- Need for tools with excellent heat and wear resistance.
Because high-speed cutting generates intense localized heat, tools must conduct heat effectively and resist thermal cracking. Diamond milling cutters, with their high thermal conductivity and low friction, maintain performance even in coolant-free environments.
Significance of Combining Dry Cutting and High-Speed Cutting
The combination of dry and high-speed cutting—known as high-speed dry cutting—is a rising standard in advanced manufacturing. It promotes high productivity while minimizing environmental impact. However, it places extreme demands on cutting tools.
Conventional tools fail quickly under such conditions due to thermal softening, wear, or built-up edge formation. Diamond milling cutters specifically engineered for dry high-speed machining offer:
- Ultra-low friction coefficients (less heat generation).
- Exceptional thermal conductivity (quick heat dissipation).
- Superior hardness and wear resistance (longer tool life).
These features make PCD and CVD diamond tools especially well-suited for dry, high-speed cutting of graphite, carbon fiber, and ceramics. They are foundational to smart manufacturing and green production.
Advantages of Diamond Milling Cutters in High-Speed Dry Cutting
Exceptional Wear Resistance and Hardness
The Vickers hardness of diamond materials is as high as 8000HV or more, far exceeding cemented carbide and ceramics, and is one of the hardest tool materials known to date. PCD diamond milling cutter exhibits extremely high wear resistance by sintering polycrystalline diamond into the tool edge, and can remain sharp even in continuous dry cutting.
This super hardness means that diamond tools are not easy to wear when processing highly abrasive materials such as graphite, carbon fiber, and high-silicon aluminum alloy, thereby greatly extending the tool life. Compared with traditional cemented carbide tools, the life of diamond milling cutters under the same cutting conditions can usually be increased by more than 5 to 20 times, making them the preferred tool for high-speed dry cutting of high-hardness materials.
Superior Thermal Conductivity Reduces Cutting Temperatures
In high-speed dry cutting, it is impossible to remove heat with the help of coolant, so the thermal conductivity of the tool is particularly critical. Diamond is one of the solid materials with the highest thermal conductivity, with a thermal conductivity of 1000~2000 W/m·K, which is far superior to cemented carbide (about 90 W/m·K).
This characteristic enables CVD diamond end mill for dry cutting to quickly conduct heat away from the cutting area, reduce the tip temperature, reduce thermal cracks and thermal fatigue damage, and significantly improve tool stability. In addition, the better the tool cooling effect, the smaller the thermal deformation of the processed material, which is conducive to ensuring dimensional accuracy and product consistency.
Cost Savings and Environmental Benefits
Traditional wet cutting relies on a large amount of coolant, which not only increases procurement and processing costs, but also involves issues such as liquid pollution, emission treatment, and wet safety in the workshop. Using diamond milling cutter for dry machining, it can run stably without using any cutting fluid, truly achieving clean processing.
Enhanced Surface Finish for Precision Applications
In addition to wear resistance and thermal conductivity, diamond tools have another outstanding advantage – extremely low friction coefficient, which means less friction heat and material adhesion during cutting. Especially when finishing graphite electrodes or ceramics, using diamond milling cutter for precision machining can effectively reduce surface scratches and built-up edge, and obtain a more uniform and delicate machining surface.
In CNC high-speed finishing, surface quality is directly related to the cost of subsequent processes and even the final part performance. Diamond milling cutters can achieve mirror-grade surfaces in one pass due to their unique material properties, effectively reducing secondary processing steps such as polishing and grinding.
Ideal Applications for High-Speed Dry Cutting with Diamond Milling Cutters
Diamond milling cutters are particularly suitable for dry cutting + high-speed cutting due to their superhardness, high thermal conductivity and extremely low friction coefficient. The following four typical processing materials have characteristics such as high abrasiveness, poor thermal conductivity or easy brittle fracture, which are the key application scenarios of diamond milling cutter dry machining.
Graphite Electrode Machining
Graphite is a highly abrasive material. During its processing, it is easy to produce a large amount of fine powder, which is extremely serious for tool wear. Conventional carbide tools are very easy to be blunted under dry cutting, while diamond milling cutter for graphite electrodes performs well in graphite electrode processing due to its super wear resistance and low friction characteristics.
PCD milling cutters and CVD coated tools are particularly suitable for roughing and finishing of graphite:
- Maintain sharp cutting edges without using coolant.
- Reduce graphite dust adhesion and accumulation.
- Obtain higher dimensional accuracy and finer surface finish.
Especially suitable for high-precision molding of EDM graphite electrodes in the mold industry, it is the preferred tool solution for dry cutting of graphite.
CFRP Machining
CFRP has an extremely high strength/weight ratio, but common processing defects such as fiber pullout, delamination, and burrs are common during cutting. Conventional tools are prone to microcrack propagation and material tearing, while the use of PCD diamond milling cutter for CFRP dry machining can significantly suppress these problems.
Its main advantages include:
- Keep the cutting edge sharp and prevent fiber tearing.
- Provide a clean fracture and edge profile.
- Dry cutting avoids thermal deformation of composite materials or softening of resin.
Ceramics and Glass Machining
Ceramic and glass are typical hard and brittle materials with high hardness and low fracture toughness. Once improperly processed, they are prone to edge collapse, microcracks or fragmentation. Traditional tools often have difficulty controlling the fracture behavior when cutting such materials, while CVD diamond end mill for hard brittle material can achieve more stable processing results with its extremely high hardness and sharp cutting edge.
Its typical applications include:
- Zirconium oxide ceramic precision parts.
- Quartz glass microgroove processing.
- Sapphire or superhard material micro-milling.
High-Silicon Aluminum Alloys and Other Nonferrous Metals
High-silicon aluminum alloys (Si＞12%) are typical difficult-to-process metal materials, commonly used in lightweight parts such as engine cylinders and aviation structural parts. Its high silicon content causes severe wear on the tool, and it is easy to generate built-up edge during high-speed dry cutting. At this time, using diamond milling cutter for high-silicon aluminum can effectively improve the processing performance.
The advantages are:
- The cutting edge is wear-resistant, which significantly extends the tool life.
- Low friction, reducing cutting heat and sticking.
- The processed surface is smooth and free of vibration marks, which is conducive to subsequent assembly and airtightness control.
This type of tool is also widely used in materials with high thermal conductivity but easy adhesion, such as copper alloys, magnesium alloys, and non-ferrous metals. It is a popular choice in the field of 3C products and new energy vehicles.
Precautions When Using Diamond Milling Cutters for High-Speed Dry Cutting
Although diamond milling cutters offer many advantages, their performance in high-speed dry cutting depends largely on the stability and setup strategy of the entire machining system. To maximize the performance of diamond tools in dry, high-speed applications, users must carefully manage the machine tool, cutting parameters, and operating strategy.
Spindle Rigidity and Tool Holder Accuracy Requirements
Diamond milling cutter edges are extremely sharp but have low impact resistance. Therefore, spindle rigidity and tool holder concentricity are critical for ensuring stable cutting. In high-speed dry cutting, any spindle runout or improper clamping can easily cause blade breakage or abnormal wear.
Recommended Practices:
- Use high-precision tool holders such as HSK or BT40/BT50.
- Control spindle runout within ≤3μm.
- Use clamping systems rated G2.5@30,000rpm or higher for dynamic balance.
A high-precision clamping system not only improves overall cutting stability but also extends the service life of PCD tools. This is especially important for precision applications like dry cutting of graphite electrodes or CFRP.
Proper Cutting Parameter Settings
Dry cutting environments lack coolant to manage heat, making them particularly sensitive to cutting parameters. Incorrect speeds or depths can lead to tool thermal fatigue or burning of the workpiece surface. Conversely, overly conservative parameters waste tool potential and reduce efficiency.
Suggested Settings (adjust based on material and tool type):
- Spindle Speed (RPM): Generally 15,000–40,000 rpm.
- Feed Rate (F): Should consider material hardness and chip evacuation.
- Depth of Cut (Ap/Ae): Light and fast cuts are recommended, prioritizing surface quality.
When dry milling hard materials with diamond tools, refer to supplier-provided parameter charts and fine-tune based on the balance between efficiency, thermal control, and tool life.
Machining Path Optimization and Vibration Prevention
High-speed dry cutting requires smooth machining paths and stable feed angles to avoid tool breakage and vibration marks on the workpiece.
Optimization Tips:
- Use spiral or arc entry to minimize sudden tool impact.
- Optimize overlap and chip flow direction to prevent heat buildup.
- Apply efficient CAM strategies to maintain consistent cutting loads.
In vibration-sensitive materials like CFRP or ceramics, path optimization is critical to ensure surface integrity and stable tool engagement.
Tool Life Management and Replacement Strategy
While diamond tools are wear-resistant, once edge wear or microcracks develop, machining accuracy and surface quality deteriorate. A systematic approach to tool life management is essential.
Best Practices:
- Use tool wear monitoring systems (e.g., spindle current or acoustic emission sensors).
- Track cumulative cutting time or area for replacement planning.
- Inspect edges under magnification to detect early wear or chipping.
- Choose PCD tools that can be resharpened for extended tool life.
Diamond Milling Cutters: Dry vs. Wet Cutting Performance
In CNC machining, both dry and wet cutting methods have their pros and cons. For diamond milling cutters, the choice of cutting mode significantly affects tool performance, machining efficiency, and finished part quality. Below is a comparison across key factors.
Machining Efficiency
One major benefit of dry cutting is the elimination of coolant, reducing setup complexity and streamlining the process. Diamond tools, with their ultra-high hardness and low friction, maintain effective cutting performance even without coolant.
Wet cutting, on the other hand, lowers the cutting temperature and extends tool life in high-heat applications. However, it adds complexity through continuous coolant supply and heat management via chip removal. Under comparable conditions, dry cutting often delivers higher production efficiency.
Surface Roughness
Dry cutting with diamond tools often yields smoother surfaces due to their wear resistance and low friction. This is particularly advantageous for graphite electrodes and carbon fiber components.
Wet cutting helps reduce heat and associated deformation, which can improve surface finish in certain hard and brittle materials. For superfinishing operations, wet cutting may produce slightly better uniformity.
Tool Wear Patterns
Dry cutting increases heat stress on the tool, potentially leading to adhesion, abrasive wear, or microcracking. Wet cutting cools the tool, reducing thermal stress but introducing chemical and adhesion wear.
For diamond cutters:
- Dry cutting wear: Primarily abrasive wear and microcracks.
- Wet cutting wear: More prone to chemical corrosion and adhesion.
Thus, dry cutting is suitable for light-duty or intermittent high-speed work, while wet cutting suits continuous, high-load machining.
Cost and Environmental Impact
Dry cutting eliminates coolant-related costs and environmental waste, aligning with green manufacturing goals. It simplifies operations and reduces hazardous disposal needs.
Wet cutting adds cost through coolant purchase, filtration, and waste management. While it can improve tool life in demanding conditions, its overall long-term cost is often higher.
The Value and Future of Diamond Milling Cutters in High-Speed Dry Cutting
Contribution to Precision Manufacturing
For ultra-precision and high-surface-quality applications, diamond milling cutters are ideal. In industries like aerospace, mold manufacturing, and medical devices, they help maintain tight tolerances and smooth finishes, improving part performance and reliability.
Diamond tools are effective on a wide range of hard and brittle materials. Their use in dry cutting improves both efficiency and sustainability, meeting modern standards for green production.
Distinct Advantages Over Coated Tools
Compared to traditional coated tools, diamond milling cutters offer superior hardness and wear resistance. In high-speed dry cutting, they maintain performance longer, particularly under high thermal loads.
While coatings enhance tool life temporarily, they’re vulnerable to thermal expansion, flaking, and wear. Diamond tools provide stable performance without coolant, reducing costs and environmental impact, and promoting clean manufacturing.
Future Trends: Nano Coatings, Multi-Axis Dry Cutting, and Smart Monitoring
The demand for high-performance tools is driving innovation in diamond cutter technology. Key trends include:
- Nano-Coatings: Next-gen diamond tools may feature nano-scale coatings to improve wear resistance, thermal shock stability, and corrosion resistance, significantly extending tool life.
- Multi-Axis Dry Cutting: Integrating diamond tools with multi-axis machines enables the efficient production of complex parts with improved precision and fewer setups—ideal for aerospace and automotive sectors.
- Smart Tool Monitoring: Industry 4.0 integration allows real-time wear detection and tool status monitoring, enabling adaptive machining, reducing downtime, and extending tool longevity.
