Machining in CNC machines is a constant element of the production process in many industrial sectors. With its help, companies can create precise tools and machine parts, used in the automotive, aviation, agricultural, or medical industry. An integral part of the metalworking process remains milling, which is cutting out pieces of metal using specialized tools with multiple blades. Milling cutters must reflect the considerable diversity of tasks undertaken in professional technology parks. Therefore, it is not surprising that multi-blade tools have seen dozens of configurations, differentiating them in terms of shape, material, geometry of cutting edges, or intended use under specific conditions. In today's article, we will present the most important types of milling cutters, without which many tasks would be impossible to perform. The choice of the optimal tool affects the efficiency of the production line and determines the quality of the later product. Therefore, it is worth familiarizing yourself with the most commonly used variants of milling cutters, adjusting the technology to your own needs.
What are the specific uses of different types of milling tools?
Milling in CNC machines is a complex process influenced by logistical, material, and IT issues. It is impossible to properly perform tasks related to CNC machining without creating an extensive set of milling cutters, ensuring precision of operation and design flexibility. The choice of a particular type of milling cutter is dictated by the requirements presented by the client and the analysis of the most efficient way to implement the assumptions. There are two basic types of milling cutters available on the market: standardized milling cutters and specialized milling cutters. In the case of the former, there is no problem with access to tools. Thanks to legal standardization, these milling cutters are available from manufacturers. The only challenge remains the selection of the appropriate shape of the milling cutter in relation to its purpose. Special milling cutters, also known as form cutters, are custom-made tools. They are used for strictly defined production purposes. Special milling cutters are mainly used for mass production of complex-shaped products.
Within the aforementioned types of milling cutters, we can distinguish many subcategories. We will present them in the following paragraphs, explaining the application of each of them. The huge diversity of milling tools results from the specifics of the CNC machine's work, which has to cope with the precise reproduction of the shape, size, and surface structure of the object, in accordance with the design in CAD software.
What is a milling cutter made of?
Since milling cutters are designed to remove portions of material and give it a target shape, they themselves must withstand enormous mechanical loads and guarantee material stability throughout the entire production process. Therefore, the manufacture of a milling cutter cannot leave a margin for error. For the production of small milling tools, high-hardness high-speed steel HSS, which has appropriate physicochemical properties, is primarily used. HSS steel milling cutters perform excellently when cutting at a low linear speed Vc.
Milling cutters made of hard sintered materials achieve another level of hardness and wear resistance, which results from the tool production process itself. Sintered milling cutters are obtained in the process of pressing and sintering metal powders, which gives the product certain quality parameters, such as purity and the desired chemical structure. Milling cutters can also be made from stainless steel covered with a diamond bulk. This type of tool performs well during CNC machining at high speed, while providing resistance to wear.
Classification of Milling Tools
Let's now move on to the description of the most important categories, according to which the divisions of milling cutters used for metal machining in CNC machines are made. When choosing tools to achieve your own goals, you should primarily be guided by the specifics of the work performed and only on this basis make a selection of the appropriate tool. Milling cutter manufacturers make the task a little easier by adding standardized markings to their products. Based on them, we will know for which materials a given product was created. Normal steel uses milling cutters marked with the letter N. An N-type shank mill has several degrees of mechanical strength. A characteristic feature of this type of milling cutters is the spiral angle of the blade, which should not exceed 30 degrees. N-type shank milling cutters work great during finishing work on structural steel.
Another type of milling cutters in CNC machining are H-type milling cutters, created for working with various materials as part of precise leveling machining. With H-type milling cutters, you can remove a welding seam or chamfer surfaces. On the other hand, NR or NF type milling cutters are intended for working with materials of the highest degree of hardness. They allow work on materials with a strength of up to 1400 N/mm2.
Classification of milling tools based on shape criterion
The placement of the blade on milling cutters determines the method of cutting in a CNC machine. Depending on the shape, we distinguish, among others, an end mill (shaft) with a screw cutting blade, a cylindrical mill (cutting blade located on the side of the tool) or a face mill (in this case, the blade is placed on the front surface). A specific combination of the tools mentioned here is a cylindrical-face mill. It is a cylindrical mill with a characteristic face driver. The design of the mill predestines it for work with hardened steel and for performing high-speed machining.
The next shape of mills available on the market is the disc mill. Disc mills are probably the most common tool for home cutting methods. However, there are specialized versions of these devices designed for work in CNC machines. An extension of the offer of disc-shaped mills is the angle mill. Its distinguishing feature is the presence of cutting blades on two cone-shaped surfaces, narrowing towards each other in the middle of the disc thickness.
The module mill (otherwise: disc mill) is perfect for giving the desired shape to gears in the automotive industry. Module mills have large sizes and enormous rigidity, which makes them an excellent choice for rough and finishing machining.
A separate version of module mills is the worm mill, used for milling splines and gears. Mounted worm mills come in numerous size versions, but all of them have a common characteristic feature - a spiral arrangement of blades surrounding the mill (hence the name: worm mill).
Classification of milling cutters based on blade geometry criterion
Milling tools can also be divided according to the geometry of the cutting blades. In this category, we find a cylindrical mill with a universal character or an angle mill designed for cutting grooves in the base material. A ball mill, which has a disc with several single-sided blades, is used for cutting raw material. Ball mills are used, among others, in carpentry companies and metal processing plants. Their small blades and high rotation speed allow for work with many materials, making ball mills tools with a high degree of universality. Cutting the base material with ball mills is fast and with high precision, which translates into a reduction of material losses.
A specialized type of equipment for CNC machine tools is a profile mill, created, among others, for creating counter profiles in frame doors. Profile mills are used wherever there is a need to finish the surface of an object with a specific profile. Like a cone mill, profile mills are used to finish an object according to the project specification. However, the use of profile mills guarantees a far-reaching autonomy of the production process, which translates into a higher work pace in the production of complex elements.
Classification by blade type criterion
It is worth mentioning the possibility of differentiating milling tools also in terms of the type of the blade itself. Within this classification, we can distinguish milling cutters with a straight blade, working in drilling mode. This is the largest group of milling tools, which has countless variants of shapes, sizes, and hardness of the construction material. Shank milling cutters with a straight blade are designed for precision machining and work in drilling mode. Other types of blades for milling cutters come in the form of a helical or alternating bevel. Small alternating bevel blades can be found in disc milling cutters.
How to choose milling cutters for a CNC machine? Outsourcing CNC machining to an external company.
Based on what we have said above, it is clear how diverse the features of CNC machine milling cutters are. The types of milling tools described here have strictly defined applications, and CNC machine operators must match the tools to the specifics of a given production line. CNC metal machining involves comprehensive knowledge of materials, milling tools, CAD software, or CNC machine calibration. In addition, there is a need to invest in a modern machine park that meets diverse production requirements. Therefore, it is not surprising that there is an increasingly popular trend among small and large industrial companies to outsource machining to specialized entities, such as Sacher CNC, which will take over the entire machining process and carry out this task with the highest precision. The choice of milling cutters for the CNC machine should be left to specialists, who are well versed in the conditions of a proper and efficient production process. Only then will we gain a guarantee of correct implementation of any project - regardless of whether it concerns a prototype or involves the launch of mass production of industrial parts.