What Are the Two General Types of CNC Milling Cutters

CNC milling is indispensable in modern manufacturing. It is a subtractive technique that produces accurate and precise parts. The cutting tools move in predetermined directions to create complex designs and patterns. You can use it for many industrial applications including aerospace engine components, surgical instruments, and automotive body panels.

The cutting tool is the heart of every CNC milling operation. The type of cutters you use will determine the success of the milling process. There are different categories of CNC milling cutters available and they fall under two broad categories; flat end mills and ball nose end mills. Read on to find out the differences between these two general types of CNC milling cutters and their applications.

What is CNC Milling

CNC milling is an advanced manufacturing technique used to create high-quality components. The cutting tool is a crucial aspect of CNC milling as it performs the required action. To use a CNC milling cutter, you mount it on a rotating spindle to selectively remove excess material from a stationary workpiece. As the tool engages, it shapes the part and gives it the intended design. 

Based on the type of CNC milling machine you are using, the spindle can rotate the cutting tool in a single or multiple directions. 3-axis CNC milling machines have a limited range of movement and the spindle is fixed in one direction. However, 5-axis CNC mills are more sophisticated. The milling cutters can move at different angles and orientations. 

What are the 2 General Types of CNC Milling Cutters

There are two main types of CNC milling cutters you can use in product development. Though they have similar modes of operation, they have different features and produce unique results. Let’s look at the two general types of CNC milling cutting tools in detail

• Flat End Mills

Flat end mills are also called square end mills. They have a cylindrical shank with multiple flutes. Flat end mills remove a large amount of material in a single pass which makes them suitable for roughing operations. The number of flutes of flat end mills varies and ranges from 2 to 8. The type you use depends on the material type and desired finish. Flat end mills with two flutes are ideal for soft materials. For hard metal like steel or when a smooth finish is desirable, use the types that have four or more flutes. 

Furthermore, flat end mills are made using different materials. The most common are cobalt, high-speed steel, and carbide. Furthermore, these milling cutters also have coatings that serve various purposes. They can be coated in titanium nitride, titanium carbonitride, or aluminum titanium nitride. They increase hardness and enhance overall performance. 

Flat end mills are used for creating slots and grooves on a workpiece. You can also employ them for facing, profile milling, plunge milling, and chamfering operations. However, this milling cutters are not ideal for curved surfaces or very complex cuts. They cause chips to build up with time.

• Ball Nose End Mills

Ball nose end mills or simply ball end mills are another important category of CNC milling cutters. They have a rounded tip that makes it possible to cut complex contours and make deep pockets. They look like ball heads with hemispherical tips. Similar to flat end mills, ball nose end mills also have different flute designs which range from two to eight. 

Furthermore, most ball nose end mills have a helix angle of 30 degrees. This length of engagement balances material removal and smoothness of the cutting edge. The shank of ball nose end mills is mainly cylindrical. However, some specialized ones may have other shapes. 

Ball nose end mills have applications in contouring and 3D profiling. You can use it to create filets, chamfers, and for engraving patterns and texts. Vibration is minimal with ball nose end mills and they produce a smooth finish. However, they come with some limitations one should be aware of. Ball nose end mills may be slow because of the slower material removal rate. Additionally, it makes majorly shallow cuts and may find it challenging to work on flat surfaces.

Flat End Mills vs Ball Nose End Mills: Differences

Flat end mills and ball nose end mills are two major CNC milling cutters you can use in product development. Knowing their differences and how they compare will help you to choose the best for your project. Let’s look at the major differences between flat end mills and ball nose end mills 

• Geometry and Shape

Flat end mills and ball nose end mills have different shapes. Flat end mills have a distinct square cutting end that is perpendicular to the axis of rotation. The end of this tool is flat which makes it useful for milling flat surfaces. Ball nose end mills, on the other hand, have a hemispherical and rounded end. This feature makes this cutter useful when creating contours or complex cuts in curved workpieces. 

• Surface Finish

You can also differentiate between flat end mills and ball nose end mills based on the surface roughness they produce. Flat end mills have a limited surface finish because the edges of the cuts can be rough. However, ball nose end mills are better and the parts have a smoother and glossy finish. Their rounded tips minimize the occurrence of tool marks and rough edges. 

• Cutting Depth

The depth of cut these milling cutters can achieve is also different. Flat end mills remove material aggressively and produce deep cuts. It mills away more material per pass and has deeper cutting depth. The cutting depth of ball nose end mills is somewhat limited. They need more passes, especially for complex contours and 3D milling. 

• Tool Life and Wear

The tool life and wear of flat end mills and ball nose end mills depend on how often you use them. However, in similar situations, a ball nose end mill will wear out faster. The cutting pressure is concentrated on the tip. You may need to frequently replace this milling cutter especially if you are using it for high fee cutting operations. 

• Tool Path Strategies

You can also differentiate between these two milling cutters based on the path they follow across the workpiece. Flat end mills are optimized for linear tool paths to create flat and straightforward features. Ball nose end mills, on the other hand, require complex and 3D tool paths. They have a curved or contoured path when milling a part. 

• Cost 

Cost is another major differentiating factor. Flat end mills are less expensive and more accessible. They have simple geometry that is easy to manufacture. For ball nose end mills, the cost may be on the high side. They are more expensive to purchase because of their complex geometry. Furthermore, the skill level needed to use a ball nose end mill is higher which adds to the overall cost. 

• Applications 

The way you use flat and ball nose end mills is different. Flat end mills have applications in machining flat surfaces and creating straightforward cuts. You can use them for face milling, plain milling, and side milling operations. Ball nose end mills, on the other hand, are suitable for applications where curves are needed. 

Table 1: Flat end mills vs ball nose end mills at a glance 

Conclusion

CNC cutters are unarguably the most important part of the milling machine. They are the ones that perform the cutting action and shape the workpiece. While there are many types of CNC milling cutters available, you can group them into flat end mills and ball nose end mills. They differ in terms of shape, geometry, and the surface roughness they produce. Before using any, you should evaluate your project requirements and the particular milling operation you want to carry out. Do you still have questions and clarifications? Reach out to a reliable CNC milling shop today.