CNC machines are very adaptable pieces of machinery. A major part of this versatility may be attributed to the wide variety of cutting tools that can be used with these machines. There is a cutter for every operation, ranging from end mills to thread mills, which enables a CNC machine to conduct a wide range of cuts and incisions in a component.
Before entering into a contract with any CNC machine shop, you are required to complete the necessary step of gaining an understanding of the tasks performed by these tools. This article will go through eleven different kinds of milling cutters, the different kinds of materials that are used to make milling cutters, and some helpful pointers to keep in mind while selecting cutters.
Cutting Tool Basics
Whenever you need to remove material from a block of any kind, you’ll need a cutting tool. The cutting tool is mounted on the spindle of a computer numerically controlled machine, which then moves in the specified direction in response to the computer’s instructions.
Material is removed from the substrate by shear deformation by the cutting tool. This is accomplished by the sharp tool rotating at high speed, chipping away at the workpiece and sending the chips flying in the opposite direction. Only one point of contact is made by certain tools, whereas others, like end mills, create many contacts with the workpiece.
Several helical grooves, or “flutes,” run lengthwise on the outside of most cutting tools used in CNC machines. You may picture the flutes as the troughs of the blade and the teeth as peaks. As they are expelled, chips removed from the workpiece follow the path of the flutes.
A cutting tool’s optimal number of flutes must be tailored to the material of the workpiece. For softer materials, a tool with fewer flutes is desirable since the wider flute width allows for more chip ejection. More flutes mean faster cutting, which is great for harder materials, but the narrower flutes might cause chip jamming.
The feed rate and spindle speed rate, as well as the kind of cutting tool being used, will all have an impact on the final chip size.
Types of Milling Cutters
There is a wide variety of milling cutters, each of which has its own set of characteristics and applications. Watching this instructional video will familiarize you with the CNC tools:
As was pointed out in the accompanying video, some of the most common milling cutters include the following:
1. End Mills
Because of their capability to cut materials in an axial direction, end mills are among the most common types of milling cutters. They are relatively comparable to drills in terms of their functionality. The CNC machine tool comes in a few distinct flavors. They are differentiated by the number of flutes they possess and the various types of noses they may have. Some could even have more than eight flutes in their collection. Among the many kinds of noses are:
- Flat: The universal tool for removing 2D features is the flat-faced end mill.
- Ball Nose: The ball-nose end mill is useful for cutting complex shapes like 3D curves and contours.
- Bull Nose: This variation seems to have a flat end and rounded edges, making it ideal for roughing and filleting, as well as other similar tasks.
2. Face Mills
This kind of milling cutter has a wider range of applications. It features a head that is flat, and the cutting blades are made of replaceable carbide. Because these cutting edges are located on the milling cutter’s side, users can only cut in a horizontal direction rather than in an axial direction. Face mills are the tools of choice for machinists when it comes to creating flat areas on raw materials.
One of the reasons they continue to be one of the greatest kinds of milling cutters is that they include cutting inserts that can be replaced. This feature allows them to last even longer and provide a higher quality of work over an extended time. It is very simple to replace the inserts, so you won’t need to purchase a new tool.
3. Slab Mills
Machining centers of the present day often do not make use of this specific kind of mill cutter. Because they lack side teeth, machinists employ them to create flat surfaces on various materials. They have flat surfaces and are designed for use in heavy-duty applications in general.
4. Involute Gear Cutters
Hobbing machines are a specialized kind of milling machine that machinists use in the production of gear cutters. The machine that is utilized to create the gear will be different based on the number of teeth that are desired in the gear.
5. Fly Cutters
Fly cutters are a more cost-effective alternative to face mills. They are made up of the primary tool body, which may have either single or double tool bits connected to it at any one time. There are a few other names for the double tool bit fly cutter, including double-end fly cutters and fly bars. Machinists make both deep and shallow cuts with them on the product they are working on.
6. Ball Cutters
Ball cutters are easy to spot because of the hemispherical cutting tip located at the cutter’s end. This tip is used to create corner curvatures on perpendicular sides.
7. Roughing End Mills
Suppose you need to remove a significant volume of material from the product in a relatively short amount of time. In that case, the roughing end mills are the CNC machine tool you should almost always turn to. The poor finish on the piece and the cutter’s lack of accuracy are the results achieved at the expense of speed. Because of their diminutive dimensions, the shards of chopped metal that it generates are usually straightforward to remove.
8. Hollow Mills
This mill seems like it was built upside down because of its pipe design. Shapes like full points and form radii may be machined with a hollow mill because of the mill’s cutting edge, which is located on the inside of the tool.
9. Woodruff Cutters
Woodruff or keyseat cutters are used by machinists to make key slots into components like shafts. For making slots that are just right for woodruff keys, the cutters contain teeth that run orthogonal to the outside diameter.
Reamers, which have a significantly tighter tolerance than other tools, are used by machinists to enlarge preexisting holes in the workpiece to the required finish and diameter.
11. Side-and-Face Cutters
This particular sort of cutter, as the name suggests, has teeth on both the side and the perimeter of its cutting tool. This cutter is used by machinists to shape slots and grooves in various materials. Even though they perform in a manner similar to that of end mills, the use of these tools has become less common as a result of advances in technology.
What Type of Materials Are CNC Machine Tools Made of?
To cut a solid workpiece, the cutting tool must be made of a rigid material than the workpiece material. And because CNC machining is generally used to make parts from very hard materials, this leads to the limitation of the number of cutting tool materials available.
Common materials used for cutting tools
- Carbon steel
Carbon steel is a cost-effective alloy steel composing 0.6-1.5% carbon, along with manganese and silicon.
- High-speed steel
More expensive high-speed steel is harder and more ductile than carbon steel due to a mix of molybdenum, chromium, and tungsten.
Often sintered with another metal such as titanium, carbide tools are wear and heat-resistant, offering an incredible surface finish.
Used for cast iron, cutting superalloys, and other tough materials, ceramic tools are corrosion and heat-resistant.
Coating for cutting tools
The functionality of a cutting tool depends on its shape and material, but can also be adjusted by coatings on the main material. These coatings can make the tool harder, extend its service life, or allow it to cut at a high speed without affecting the part.
Common coatings available for cutting tools include:
- Titanium Nitride (TiN)
Titanium nitride is a general-purpose coating with a high oxidation temperature helping enhance the hardness of cutting tools.
- Titanium Carbo-Nitride (TiCN)
Titanium carbo-nitride increases the surface lubricity and hardness of cutting tools.
- Ultra-Life Titanium Nitride (Al-TiN)
Al-TiN increases the heat resistance of carbide-cutting tools, especially when using minimal coolant.
Diamond coating on a cutting tool demonstrates high performance for cutting abrasive materials.
- Chromium Nitride (CrN)
Chromium nitride increases the corrosion tolerance and hardness of cutting tools.
Tips to Consider Before Selecting Milling Cutters
When you are required to use the tool at high temperatures or when you have to cut through materials that are particularly hard, selecting the appropriate cutter for your work may be a challenging endeavor. Before selecting the appropriate milling bit, there are a few things to remember, including the following:
The Material the Tool Is Made From
High-speed steel continues to be one of the greatest choices available regarding various kinds of tools. When it comes to toughness and hardness, it offers the advantages of both worlds to the user. Nevertheless, the kind of tool that you choose could be dictated by the requirements that you have. You could fare better with cutting ceramics or cemented ceramides if you require a tool that is very hard for work that will only last for a limited amount of time.
It is important to pay attention to the kind of tool coating that your CNC machining tool possesses. Using coatings such as titanium nitride extends the tool’s useful life but also drives up its cost. Additionally, there are coatings that reduce tool stickiness, minimizing the need for lubrication on the job and further lessening the cost.
Number of Flutes
Milling bits have grooves, or flutes, that allow for cutting. A milling bit’s feed rate is set by the number of flutes it has. Nonetheless, a big milling bit with a massive number of flutes implies less room for metal shavings to escape the workpiece.
A Right Choice for CNC Machining – Runsom Precision
While this article discusses the different types of cutters available for CNC machines, there are still many other factors to consider before deciding on the right one for your job. A correct choice will always be determined by material selection, the geometric complexity of your design, required tolerance, and others. Sometimes, one cutting tool is enough; other times, you may need to rely on two or more cutting tools to make your part.
Please contact us and talk about your project, so our experts can help you with a perfect selection of cutting tools, exact materials, and the proper manufacturing process ideal for your task, or you can request a fast quote for free online to get started with your CNC machining project right now.
Other Articles You May be Interested in: