A lathe machine is used to shape and cut wood and metal by rotating the workpiece and getting rid of unwanted material. CNC lathe machines, however, have completely changed and revolutionized the game by increasing efficiency and bringing greater precision to the cutting operations.
Speaking of cutting tools, they are the core element of the CNC lathe machine as they define and shape the final product. Hence, selecting the right cutting tool is of immense importance for producing high quality parts, extending the tool life, and optimizing efficiency.
This guide will look into the different cutting tools for CNC lathe machines, their features, their properties, when and how they should be used. Not just that, by the end of the article you will also know how to maintain these tools and why exactly should be the criteria for the selections. Let’s dive in.
With the upgradation of manual lathe cutting machines to CNC lathe machines, they are taking over every manufacturing industry like anything. CNC machines are fully automated and run by a data drive program that controls the cutting tools and operations to ensure precision and efficiency. More and more industries and making the most out of CNC lathe machines; automotive, electronics, furniture manufacturing industry to name a few.
Looking at the increasing reliance on and importance of CNC lathe machines, it should be known that their key element is the cutting tools attached to them. These are the tools that actually do the work, for instance, cutting, drilling, boring, threading, and anything that is the need of the workpiece.
The wide variety of cutting tools can be further divided into categories, that eventually helps in determining what exactly is the need. The classification is based on the basis of material, or the purpose, or the cutting edges required.
The material the CNC lathe machine is dealing with will impact the cutting tool that is selected. This is because different materials respond differently to various types and hence it should be taken into consideration which material will go in contact with the cutting tool to ensure greater efficiency. Cutting tools have a major role on its performance, including wear resistance, the cutting ability and the resistance to heat.
1. High speed steel (HSS)
HSS tools are known for their rigidness and their durability. They are used where the high-speed machining is not required and where cost is rather more of a concern. Although, they cost less than the other materials they are also less resistance to heat and wear which means they wear out more quickly.
2. Ceramic
Ceramic cutting tools are highly resistant to heat which means they are perfect for high-speed machining of toughened material. They can also bear high cutting speeds without the need for any coolants, but they can crack under high mechanical stress.
3. Carbide
This is the most commonly used cutting tool in CNC lathe machines, made out of tungsten carbide and are heavily relied on for their hardness, wear resistance and to provide with the sharpness during high cutting speeds. This cutting tool material is ideal for metal workpieces. However, this can also chip under heavy impact.
4. Cermet
This cutting tool is an amalgamation of ceramic and metallic materials which ultimately make it ideal for dealing with toughness. Cermet cutting tool gives good finishing operations.
Another criteria for CNC lathe tools is on the basis of the machining operation. Hence the operations should be a factor while considering the tools.
1. Turning tools
This tool is used in turning operations where a specific shape or dimension of the workpiece is achieved by removing the material from the outer diameter of a cylindrical workpiece. Turning is the most common operation and it can be further in divided based on the material removal rate over surface finish.
For instance, roughing turning tools are made to deal with bulk material removal as they have larger nose radius. They also have stronger cutting edges which enables easy handling of heavy cutting forces.
Next up is Finishing turning tools which have smaller nose radius and they provide with smooth surface after roughing. However, they provide with lower raters of material removal in comparison to roughing.
The last one is profile turning tool which is used for complex external profiles and requires precise geometry to follow the specified profile and maintain accuracy.
2. Boring tools
Boring tools are necessary for internal machining because they expand or finish pre-drilled holes in a workpiece, resulting in exact internal diameters and high-quality surface finishes.
Rough boring tools are intended to remove huge volumes of material in the early phases, resulting in the basic interior shape.
After rough boring, finishing boring tools are used to increase precision and surface quality, ensuring that the final dimensions match the exact specifications.
Precision boring bars are used for high-precision internal machining because they provide delicate control and tight tolerances, which are critical in applications that require extreme precision. These tools are essential for creating smooth, accurate interior surfaces.
3. Parting and grooving tools
Parting and grooving tools have unique tasks, yet they are frequently used interchangeably in CNC lathes. Parting tools, also known as cutoff tools, are narrow, sharp-edged tools used to separate components from a larger workpiece by cutting along a single axis.
Grooving tools, on the other hand, are meant to cut grooves or channels into the surface of a workpiece. These can be internal, such as holes or bores, or external, along the workpiece's diameter or face, with profiles adapted to varied groove geometries.
4. Drilling tools
Drilling tools are used to create round holes in the workpiece and are often the initial operation in CNC lathe machining, laying the foundation for further processes like boring or threading. The twist drill is the most common type, featuring a helical shape that aids in chip removal as it cuts through the material. Twist drills are versatile and used for a variety of materials in initial hole-making. Center drills, on the other hand, create small pilot holes that guide larger twist drills, ensuring the drill remains centered and preventing deflection during machining.
5. Threading tools
Threading tools are used to cut screw-like threads on the external or internal surfaces of a workpiece, with specific geometries to ensure accurate and uniform thread profiles. External threading tools are designed to cut threads on the outer diameter of cylindrical workpieces. Their cutting edges are shaped according to the required thread profile, with CNC programming ensuring precise pitch and depth. Internal threading tools perform the same function inside bores or holes, creating internal threads that must match the external thread profile precisely for proper fitting, making them critical in applications requiring threaded components.
6. Knurling tools
Knurling tools are used to create textured or patterned surfaces on cylindrical workpieces, primarily for aesthetic or functional purposes, such as enhancing grip on handles or fasteners. Straight knurling tools create parallel ridges along the surface, providing a simple linear pattern. Diamond knurling tools, on the other hand, produce a crisscross or diamond-shaped pattern on the workpiece's surface, which is commonly used for better grip, making it ideal for applications where handling or friction is important. These patterns can be applied to both metal and plastic workpieces for various functional or decorative uses.
1. Single-Point Cutting Tools
Single point cutting tools have a single cutting edge that interacts with the workpiece, making them suitable for tasks including turning, boring, threading, and chamfering. These tools are ideals simple machining applications that demand precision in a single direction. They are straightforward to make because to their basic geometry and are ideal for precision machining where great accuracy is required.
2. Multi-Point Cutting Tools
Multi-point cutting tools, as the name implies, have many cutting edges, which engage with the workpiece concurrently, resulting in higher material removal rates and lower tool wear. They are commonly used in operations that need great productivity, such as drilling, milling, and reaming.
The many cutting edges also improve heat dissipation, increasing tool longevity and performance. It should also be known that while they are more efficient than single-point cutting tools, they have got more complicated geometry as well.
Speaking of geometry, then it is very important while talking about the CNC lathe machines and its cutting tools because it determines how it interacts with the workpiece and impacts various machining results.
The rake angle, or the angle between the cutting tool's face and the workpiece surface, is an important geometric aspect. The rake angle has a considerable influence on cutting force, chip formation, and overall tool wear. A positive rake angle is commonly utilised when machining softer materials because it minimises cutting resistance and facilitates chip production. For tougher materials, a negative rake angle is desirable because it increases tool strength and chip resistance.
Another essential element is the relief angle, which is the angle formed between the cutting edge and the workpiece surface. This angle prevents the tool from rubbing against the workpiece, minimizing friction and wear. However, choosing the appropriate relief angle is critical. If the relief angle is too large, the tool will be weaker and more likely to shatter. On the other hand, a tiny relief angle might produce excessive friction, resulting in overheating and premature tool wear.
The cutting-edge radius also affects the ultimate finish of the machined surface. A greater radius produces a better surface finish but requires more cutting force. In contrast, a smaller cutting-edge radius produces sharper, more aggressive cuts but may not deliver as fine a surface quality. Finally, the nose radius (the rounded tip of the cutting tool) strengthens the tool and improves surface smoothness. However, if not properly handled, a wider nose radius can increase cutting pressures and create tool chatter, reducing tool life and workpiece quality.
Cutting tools are frequently mounted on tool holders in CNC lathe machines, which are essential for stability and accurate machining processes. Tool holders are made to hold the cutting tool firmly in place while maintaining the ideal cutting angle for efficient results. Indexable tool holders are one of the most often used varieties of tool holders. These holders employ indexable inserts, which are changeable cutting tips composed of ceramic or carbide.
They are rather a more cost efficient way of changing the nibs when they give up instead of replacing the whole machine.
When performing single-point cutting tasks like turning or boring, rigidity and accuracy are crucial. Quick-change tool holders are commonly used in high-volume CNC machining to minimize tool change downtime. These holders are extremely useful for applications where frequent tool changes are required to maintain efficiency since they enable quick tool shifting without the need for recalibration.
The actual indexable inserts are available in three different shapes: round, square, and triangle, each of which is appropriate for a certain machining activity. Additionally, various coatings like diamond-like carbon (DLC) and titanium nitride (TiN) are available for them, which increase wear resistance, lower friction, and lengthen tool life.
To get the best results from CNC lathe operations, the correct cutting tool must be chosen. The workpiece material is one of the most important variables since different materials call for distinct tool qualities. While softer materials like plastic or aluminum can be machined using high-speed steel (HSS) tools, which are less expensive but less wear-resistant, harder materials like titanium or stainless steel require robust tool materials like carbide or ceramic to endure high heat and wear.
Furthermore, feed rate and cutting speed are critical since greater speeds result in increased wear and heat. HSS is better suited for slower operations, while carbide tools perform better in high-speed machining. Lastly, the cost and tool life are important factors. Although high-performance tools, such as inserts made of polycrystalline diamond (PCD) or cubic boron nitride (CBN), are more costly, they last longer and minimize tool changes and downtime, which lowers overall production costs.
Tool Maintenance and HandlingTo ensure precision in machining and prolong the life of tools, proper maintenance is essential. It's crucial to regularly check for wear, chipping, or breaking. It's best to repair damaged tools right away to prevent machining quality issues. Indexable inserts should be stored in their original packaging to prevent damage, and rust and corrosion can be avoided by storing them in dry, clean settings. Re-sharpenable tools, such as HSS, can last longer with regrinding; worn carbide and ceramic inserts need to be changed. Applying the proper quantity of coolant also minimizes tool wear, lowers heat, and enhances surface finish.
ConclusionIn order to maximize CNC machining productivity and efficiency while lowering costs and tool wear, it is essential to understand the right selection and maintenance of lathe cutting tools. But it also comes down to the quality of the cutting tools for CNC lathe machine you are using in your industry. One best stop for all of your CNC lathe machine related stuff is CNC Yangsen. With more than 20 years of experience and highly strict quality control measures in place, we ensure that your needs are fulfilled just the way you want.
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