The Differences And Applications of 2 3 4 And 6 Blade Milling Cutters

A comprehensive analysis of the number of milling cutter blades: the differences and applications of 2-, 3-, 4- and 6-blade milling cutters

 Core structural differences:

The choice of the number of milling cutter blades has a profound impact on processing efficiency, surface quality and tool life. Its core differences are reflected in three mutually restrictive structural characteristics:

The inverse relationship between the chip groove space and the number of blades: The increase in the number of blades directly leads to a decrease in the chip groove space allocated to each cutting edge. The 2-blade milling cutter has the largest chip groove volume and a spacious chip discharge channel, which is particularly suitable for deep groove processing and high removal rate scenarios. The 6-blade milling cutter has the most cramped chip groove space and is mainly used for finishing13.

The proportional evolution of tool rigidity and the number of blades: The increase in the number of blades means an increase in the tool core diameter. 4-blade and 6-blade milling cutters provide higher rigidity through the enhanced tool body, have strong resistance to cutting force deformation, and perform well in side milling and hard material processing. In contrast, the 2-blade milling cutter has weaker rigidity and is prone to deflection in deep groove processing38.

Continuous spectrum of blade number characteristics: Different blade numbers form a continuous spectrum of balance between chip evacuation ability and processing accuracy. 2-blade and 3-blade milling cutters tend to prioritize chip evacuation, while 4-blade and 6-blade focus on accuracy and rigidity. Users can choose the most suitable blade number in this spectrum according to their needs78.

Table: Comparison of core structural parameters of milling cutters with different blade numbers

Number of blades Chip groove space Tool rigidity Main advantages

2-blade Extremely large ✓✓✓✓ Low ✓ Deep groove processing, high chip evacuation requirements

3-blade Large ✓✓✓ Medium ✓✓ Comprehensive performance of aluminum alloys

4-blade Medium ✓✓ Good ✓✓✓ General processing of steel parts

6-blade Small ✓ Excellent ✓✓✓✓ Finishing, high surface quality

2 Detailed explanation of milling cutters with different blade numbers

2.1 2-blade milling cutter: Deep groove processing expert

Structural characteristics: The two-blade design creates a wide chip evacuation channel, and the groove depth can reach more than 1.5 times the diameter. The helix angle is usually designed to be 30°-45°, and the sharp positive rake angle (usually ≥10°) ensures that the chips quickly leave the workpiece15. This structure enables the 2-edge milling cutter to effectively avoid tool damage or breakage caused by chip blockage when processing sticky materials.

Applicable scenarios: Especially good at deep cavity milling, full-width groove processing and low-rigidity workpiece processing. For example, in mold manufacturing, the 2-edge milling cutter can easily cope with deep and narrow flow channel processing. Even if the groove depth reaches more than 5 times the tool diameter, it can still maintain relatively smooth chip removal310. Its typical application parameters are: when cutting aluminum alloy, the speed can reach 25000rpm, the feed rate is 1500mm/min, and efficient roughing is achieved6.

Performance limitations: The small number of blades leads to a decrease in cutting points per unit time, and the feed per tooth needs to be increased to maintain efficiency, which is easy to cause vibration; at the same time, the tool rigidity is insufficient, and it is easy to bend and deform during side milling, affecting the verticality of the wall19.

2.2 3-edge milling cutter: a powerful tool for aluminum alloy processing

Design balance point: The three-edge structure achieves a golden balance between 2-edge and 4-edge: it not only retains sufficient chip removal space (about 75% of the 2-edge milling cutter with the same diameter), but also adds a cutting edge to improve processing efficiency. Its unique design includes asymmetric groove arrangement, which effectively suppresses periodic vibration; at the same time, it adopts a large helix angle design (usually 45°) to improve chip removal fluency56.

Special advantages for aluminum alloys: Optimized specifically for aluminum alloy characteristics:

Use polished front cutting edge to reduce aluminum chip adhesion

Use ultra-fine grain carbide substrate to enhance cutting edge sharpness

Recommend uncoated or diamond-coated versions to avoid chemical reactions between TiAlN and aluminum56

Actual processing data shows that when a φ6mm three-edge milling cutter processes aluminum alloy, the recommended parameters are a speed of 12000rpm, a feed of 1200mm/min, and a lateral cutting depth of 0.6mm, which far exceeds the metal removal rate of 2-edge or 4-edge milling cutters with the same diameter6.

Limitation of slot processing: There is usually a process hole in the center of the end face of a three-edge milling cutter, which makes it impossible to cut vertically (it cannot be used for drilling). This limitation requires that the cutting method such as ramp milling or spiral milling must be used during processing46.

2.3 4-edge milling cutter: All-round player for steel parts

Structural reinforcement: The four-edge design expands the core diameter of the tool to more than 70% of the diameter, significantly enhances the rigidity, and can withstand greater lateral cutting forces. The double chamfered back angle design (the first back angle is about 15°, the second back angle is 9°) is adopted to reduce the friction of the back tool face while ensuring the strength of the cutting edge18. Although its chip groove is smaller than that of a 2-edge/3-edge milling cutter, the effective discharge of steel chips can still be guaranteed by optimizing the groove curve.

Advantages of steel processing: Excellent performance in processing hard materials such as steel and cast iron:

Four cutting edges achieve continuous cutting and high processing stability

High rigidity design suppresses chatter and improves surface finish

Supports higher feed rate (80-100% higher than 2-edge at the same speed)

Experimental data shows that under the same diameter, the life of 4-edge milling cutter is about 40% longer than that of 2-edge milling cutter, especially in side milling8.

Multi-functional application: In addition to conventional end milling, it is also good at:

Shallow groove finishing (groove depth ≤ 1 times the diameter)

Step surface milling

Thin-walled parts processing (high rigidity to reduce tool yield)

Profiling milling (with R angle design)78

2.4 6-edge milling cutter: high-speed finishing expert

Extreme rigidity design: The six-edge structure pushes the tool core diameter to the limit (about 85% of the diameter) to create ultra-high torsional rigidity. With a small helix angle design (about 30°), it ensures system stability when multiple blades are involved in cutting at the same time78. This design is particularly suitable for high-speed machining centers with high speed and fast feed conditions.

Advantages of finishing: Multiple cutting edges achieve fine surface processing:

Feed amount per tooth can be reduced to 0.02-0.05mm/z

Surface roughness can easily reach within Ra0.8μm

High-density cutting points eliminate chatter marks and improve contour accuracy2

The case shows that when the cutting speed is 150m/min and the feed per tooth is 0.05mm/z, the surface roughness of the 6-edge milling cutter can reach Ra0.8μm, while the 3-edge milling cutter is only Ra1.6μm2 at the same cutting speed and feed of 0.1mm/z.

Solution to the chip removal challenge: To address the problem of narrow chip space between blades, modern 6-blade milling cutters adopt innovative designs:

Variable lead spiral groove: break harmonic resonance

Uneven tooth spacing: suppress periodic vibration

Internal coolant channel design: high-pressure coolant directly reaches the cutting area, forcing chip removal78

3 Performance comparison analysis

The processing performance of milling cutters with different numbers of blades varies significantly, and a systematic evaluation from multiple dimensions is required:

Material removal rate comparison: At the same spindle speed, the increase in the number of blades directly increases the amount of cutting per unit time. The theoretical metal removal rate of a 4-blade milling cutter is 70-90% higher than that of a 2-blade milling cutter, and a 6-blade milling cutter can reach more than twice that of a 2-blade milling cutter. However, in actual processing, 2-blade/3-blade milling cutters often show higher efficiency in the roughing stage due to their greater cutting depth capability19. For example, in deep cavity milling, a 2-blade milling cutter can cut 3 times the diameter at a time, while a 4-blade milling cutter is usually limited to 1.5 times the diameter.

Surface quality difference: Increasing the number of blades significantly improves the machined surface:

The surface roughness of a 4-blade milling cutter is about 30% lower than that of a 2-blade milling cutter

A 6-blade milling cutter can achieve a mirror effect (Ra≤0.4μm) in finishing

Multi-blade milling cutters reduce the processing residual height and reduce the subsequent polishing workload28

Table: Performance comparison of milling cutters with different blade numbers for processing aluminum alloys (φ6mm tool)

Number of blades Recommended feed (mm/z) Cutting depth (mm) Surface roughness Ra (μm) Applicable process

2-blade 0.08-0.15 9.0 (1.5×D) 1.6-3.2 Deep groove roughing

3-blade 0.07-0.12 6.0 (1.0×D) 0.8-1.6 Comprehensive processing

4-blade 0.04-0.08 3.6 (0.6×D) 0.8-1.2 Side wall semi-finishing

6-blade 0.02-0.05 2.4 (0.4×D) 0.4-0.8 Finishing

Cutting force and vibration: The increase in the number of blades leads to an increase in the number of blades involved in cutting at the same time, and the total cutting force increases by about 30% (2 blades → 4 blades). However, multi-blade milling cutters reduce the cutting force of a single tooth by spreading the load, which is beneficial to suppress high-frequency vibration19. In actual processing, the amount of cutter reduction during side milling of a 4-blade milling cutter is only 40% of that of a 2-blade milling cutter, which greatly improves the verticality of the wall surface.

Evaluation of chip removal capacity: A 2-blade milling cutter exhibits excellent chip removal performance when processing sticky materials (such as aluminum and copper), and the chip holding capacity can reach more than twice that of a 4-blade milling cutter. When a 6-blade milling cutter is used for peripheral milling (non-full groove processing), the chips are not blocked in the groove, so it can still maintain a good chip removal effect38.

4 Differences in applicable materials

Different workpiece materials have a decisive influence on the selection of the number of milling cutter edges:

Non-ferrous metals such as aluminum alloys:

2-3 edges are preferred: large chip grooves to deal with sticky chips

Large helix angle design (≥45°): improve chip removal efficiency

Special aluminum tools: polished front face + sharp cutting edge (front angle ≥15°)

Avoid multi-edge coated tools: uncoated or diamond coated is best to prevent built-up edge56

Case: An automotive parts factory processes aluminum alloy connecting rods. After changing the 4-edge milling cutter to a 3-edge special aluminum milling cutter, the metal removal rate increased by 60%, the tool life was extended by 3 times, and the long-standing chip entanglement problem was solved6.

Steel and cast iron:

Recommended 4-edge: balance rigidity requirements and chip removal requirements

Medium helix angle (30°-35°): balance cutting stability and chip removal

Wear-resistant coating application: TiAlN/AlCrN coating improves hardness

Small diameter optional 6-edge: 6-edge milling cutter below φ10mm significantly improves finishing efficiency 810

Special scenario: When processing stainless steel, if high-pressure internal cooling is used, a 6-edge milling cutter can be used