An In-Depth Guide to Various Lathe Cutting Tools Used in CNC Turning

The world of CNC machining operates on precision and accuracy, at the heart of this intricately designed network are lathe cutting tools, the cornerstone of CNC turning. Each uniquely tailored tool caters to a specific task, playing a vital role in shaping, trimming, and altering workpieces to match the required specifications.

The significance of lathe cutting tools in the realm of CNC turning extends to the core of the manufacturing process. They not only enable the precise creation of parts but also enhance production efficiency and reduce waste. The selection of the correct tool directly impacts the quality of the end product, making it an indispensable aspect of CNC operations.

Various Lathe Cutting Tools

Type 1: Lathe Cutting Tools Made by Material

In the domain of CNC machining, the material of a lathe cutting tool significantly impacts its performance and the outcome of the operation. Understanding the various materials utilized in the manufacturing of these tools is essential in choosing the right one for your specific needs.

1. High-Speed Steel (HSS)

High-Speed Steel or HSS tools are an integral part of the CNC turning process. Known for their durability and resistance to high temperatures, they maintain a sharp edge even under strenuous use. These tools are highly suited for machining steel materials and machining stainless steel materials, rendering them indispensable for various industrial applications.

2. Carbide Cutters

When it comes to handling hard materials, Carbide Cutters come to the fore. Their excellent hardness and heat resistance make them ideal for long-term cutting processes.

3. Diamond Lathe Tools

Diamond, as the hardest known material, naturally finds use in the most demanding machining tasks. Diamond Lathe Tools offer unparalleled precision, making them essential for fine detailing and precision machining.

4. Cubic Boron Nitride Cutters

Cubic Boron Nitride Cutters sit at the pinnacle of cutting tool technology. With hardness second only to diamond and high thermal stability, they are particularly suited for machining hardened steel and other superalloys.

Type 2: Lathe Cutting Tools According to Operation

1. Turning Tools (Rough & Finish)

Turning tools are utilized to remove material from the exterior of the workpiece to alter its shape or size. There are two main types:

• Rough Turning Tools: These are employed for the initial cutting stage, removing large amounts of material quickly. They are characterized by their robust build to handle the high-stress environment of CNC turning.
• Finish Turning Tools: They come into play after the rough turning process to provide a fine finish to the workpiece. Finish turning tools are renowned for their precision and are a vital part of any CNC machining project.

2. Beveling Tools

Beveling tools, as their name suggests, are used to create angled edges or bevels on a workpiece. They play a significant role in welding preparation and in creating decorative finishes.

3. Thread Forming Tools

Threads are ubiquitous in mechanical parts. Thread Forming Tools are therefore crucial in manufacturing sectors. These tools are designed to cut accurate threads, making them indispensable for creating bolts, screws, and other threaded parts.

4. Surface Facing Tools

These tools are specifically designed to create flat surfaces on the face of a workpiece. Surface Facing Tools are used to prepare surfaces for further machining or for creating specific finished surfaces.

5. Shaping Tools

Shaping tools cut in a linear motion to shape the workpiece. These tools are used when precise shapes and forms are needed, such as in the creation of keyways or gear teeth.

6. Trenching Tools

Trenching tools are utilized to create deep cuts or grooves in a workpiece. They’re vital for a variety of applications, such as creating channels for wiring or cooling.

7. Hollowing Tools

These tools carve out material from the interior of a workpiece, hollowing it out. Hollowing Tools are used in making hollow components such as pipes or tubes.

8. Texture-Inducing Tools

Texture-inducing tools add patterns or textures to a workpiece, enhancing its aesthetic appeal or adding a functional surface, such as a grip.

Type 3: Lathe Cutting Tools According to Structure

1.Single Body Tools

These are cutting tools where the entire tool, including the cutting edge, is made from one single piece of material. This is often high-speed steel or some form of carbide. Single body tools can be re-sharpened multiple times until they become too small or break.

2.Welding Lathe Cutting Tools

These tools have a small piece of hard cutting material, such as carbide, welded onto the end of a tool made from a less expensive, softer material. The benefit of these tools is that they combine the cutting efficiency of hard cutting materials with the cost-effectiveness of softer tool bodies.

3.Clamp Lathe Cutting Tools

These cutting tools have a separate cutting insert which is clamped onto a tool holder. The tool holder is usually made from a less expensive material. The cutting insert can be easily replaced when it becomes worn or broken, which makes these tools convenient for high-volume or heavy-duty machining work. The inserts are available in a range of shapes and sizes for different applications.

Type 4: Coating of Lathe Cutting Tools

1. Titanium Nitride (TiN)

Titanium Nitride (TiN) is a golden, ceramic material that is often applied as a coating to cutting tools. This coating increases the hardness of the tool and allows it to operate at higher temperatures, resulting in a longer tool life. It also reduces friction between the tool and the workpiece, improving the quality of the finish and making the cutting process more efficient.

2. Titanium Carbonitride (TiCN)

Titanium Carbonitride (TiCN) is harder and more wear-resistant than TiN, and it’s known for its excellent adhesion to the base tool material. It’s generally used for applications that require high cutting speeds and feeds, and it can effectively cut harder materials.

3. Titanium Aluminum Nitride (TiAlN)

Titanium Aluminum Nitride (TiAlN) provides superior heat resistance compared to both TiN and TiCN, allowing the tool to operate at even higher temperatures without losing its cutting edge. It’s typically used for high-speed machining of alloyed steels and other heat-resistant materials.

4. Diamond-Like Carbon (DLC)

Diamond-Like Carbon (DLC) coatings offer an excellent balance of hardness, lubricity, and adhesion. They’re especially useful in applications where low friction is important, such as in non-ferrous materials or plastics.

5. AlCrN (Aluminum Chromium Nitride)

AlCrN coating offers high heat resistance, making it perfect for high-speed machining applications. The coating improves tool life significantly and enables higher feed rates.

Type 5:Geometry of Lathe Cutting Tools

1. Rake Angle

The rake angle is the orientation of the tool’s leading edge relative to the workpiece. It significantly impacts the tool’s ability to shear the workpiece material and can influence the surface finish and tool life. A more positive rake angle can make the cutting process easier, while a more negative rake angle tends to be more durable but requires more force.

2. Relief Angle

The relief angle, also known as the clearance angle, is the angle between the tool’s cutting edge and the part of the tool that trails behind it as it cuts into the workpiece. It helps ensure that the only part of the tool in contact with the workpiece is the cutting edge. This prevents unnecessary friction and wear on the tool.

3. Lead Angle

The lead angle refers to the angle between the cutting edge of the tool and the line perpendicular to the direction of the feed. It determines the width of the cutting section. A small lead angle results in a wider cut and a smoother finish but can put more stress on the tool, while a large lead angle makes a narrower cut.

4. Tool Nose Radius

The tool nose radius is the rounded edge at the tip of the cutting tool. A larger nose radius can result in a better surface finish and longer tool life but may require a larger minimum depth of cut.

Type 6: Lathe Cutting Tools according to Feed Direction

1. Right-Hand Cutting Tools

Right-hand cutting tools are designed for operations where the tool feeds from left to right relative to the operator’s viewpoint. These tools have their cutting edge on the right side and are typically mounted to the left of the workpiece.

They are the most common type of cutting tools used on lathes, and they’re employed in a wide range of machining tasks including turning, threading, and facing.

2. Left-Hand Cutting Tools

Left-hand cutting tools, on the other hand, feed from right to left relative to the operator’s viewpoint. These tools have their cutting edge on the left side and are typically mounted to the right of the workpiece.

They are often used for certain specific operations, such as machining the ends of a workpiece, where a right-hand tool may not be suitable.

3. Rounded Lathe Cutting Tools

Rounded lathe cutting tools, also known as round-nose tools, have a rounded cutting edge and can feed in any direction. The rounded shape of the tool’s cutting edge provides a wider area of contact with the workpiece, which can result in a smoother finish.

They are often used for operations that require a high-quality surface finish, such as finishing or fine turning.

Choosing the Correct Lathe Cutting Tool: Factors to Consider

Considerations for Selecting an Appropriate Lathe Cutting Tool

• Tool Material: The material of the cutting tool must be harder than the workpiece. High-speed steel (HSS), tungsten carbide, and cubic boron nitride (CBN) are some popular materials used in lathe cutting tools. The choice depends on the hardness and the heat resistance required for the operation.
• Tool Geometry: This includes parameters such as tool angle, relief angle, rake angle, and nose radius, which influence the quality of the cut and tool life. The optimal tool geometry depends on the material of the workpiece and the type of operation.
• Type of Operation: Different operations like turning, facing, boring, and threading require different types of tools. Ensure you select a tool designed for your specific operation.
• Machine Tool Rigidity: The rigidity and size of your lathe also influence the choice of the tool. For example, heavy and rigid lathes can withstand more force, allowing for the use of larger and more aggressive cutting tools.

Role of Coatings and the Material of the Workpiece

The effectiveness of a cutting tool can also be influenced by the type of coating applied to it and the material of the workpiece.

• Coatings: Coatings such as Titanium Nitride (TiN), Titanium Carbon Nitride (TiCN), and Aluminum Oxide (Al2O3) are often applied to cutting tools to improve their performance. These coatings can increase the tool’s hardness, heat resistance, and lubricity, leading to a longer tool life and better finish.
• Workpiece Material: The hardness, toughness, and thermal properties of the workpiece material determine the cutting tool material and geometry. For instance, harder materials may require a tool with a larger relief angle to reduce the heat generated during cutting, while softer materials may need a sharper tool to achieve a better finish.

Factors Depending on the Required Shape and Type of Turning Operation

The shape you want to achieve and the type of turning operation you’re performing also play a significant role in your choice of cutting tool.

• Shape: If you need to produce a complex shape, you may need to use several different tools in a specific sequence. The tool selection for roughing (removal of large amounts of material) will be different from the tool selection for finishing (creating a smooth surface or precise dimensions).
• Type of Turning Operation: Certain tools are better suited to specific operations. For example, parting tools are used for cutting off (or parting), knurling tools for creating textured surfaces, and boring bars for enlarging or finishing the inside diameter of a hole or cylindrical surface.

Key Components of A Lathe Cutting Tool

Understanding the components of a lathe cutting tool is crucial for efficient and effective machining. Let’s take a look at some of the common parts:

1. Shank: The shank is the part of the cutting tool that is held by the tool holder or tool post on the lathe. The shank provides a rigid and stable platform for the cutting edge.
2. Cutting Edge: The cutting edge is the part of the tool that actually performs the cutting action. It is typically angled and sharp.
3. Tool Nose: The tool nose is the rounded part of the tool that is often in contact with the workpiece during machining. The radius of the tool nose can influence the surface finish of the workpiece. A larger nose radius can provide a better finish but may increase cutting forces, while a smaller nose radius can reduce cutting forces but may leave a rougher finish.
4. Tool Tip or Insert: Many lathe cutting tools, especially those used in metal turning, feature a replaceable tip or insert. This insert, often made of materials like carbide, CBN, or ceramic, is the part of the tool that directly contacts the workpiece and performs the actual cutting. The inserts can be easily replaced when they wear out, which extends the life of the tool.
5. Flutes: Some lathe cutting tools, such as drills and reamers, have helical grooves known as flutes. These flutes allow chips produced during the cutting process to be evacuated away from the cutting area.

Lathe Cutting Operations: What’s Possible?

1. Turning: This is the most common operation performed on a lathe. It involves removing material from the workpiece to reduce its diameter. Turning can be performed along the exterior (outer diameter turning) or the interior (inner diameter turning or boring) of the workpiece.
2. Facing: Facing is an operation used to create a flat surface at the end of the workpiece or to cut the workpiece to a specific length. The tool feeds across the end of the workpiece, removing material layer by layer.
3. Grooving: Grooving is a process where narrow, trench-like cuts are made on the workpiece, often to facilitate parting off or to create a specific feature in a part. This operation typically uses a narrow-edged tool.
4. Parting Off: Also known as cutting off, this process is used to separate a finished or semi-finished part from the main workpiece. The tool makes a deep, radial cut that separates the part from the remaining stock.
5. Beveling: Beveling is an operation that angles the edge or ends of a workpiece. This can be done for aesthetic reasons, to prepare the piece for welding, or to remove sharp edges.
6. Drilling: Lathes can also be used for drilling operations. The workpiece is held stationary while the cutting tool, typically a drill bit, rotates and advances into the workpiece to create a hole.
7. Threading: Threading operations can be done on a lathe to create internal or external screw threads. The lathe’s ability to precisely control the rotation of the workpiece makes it ideal for threading operations.
8. Knurling: This is a process where a pattern is rolled onto the surface of a part, usually for grip. It doesn’t remove any material but rather displaces it to create a raised surface pattern.
9. Texture-Inducing: Lathes can be used to induce various textures on the surface of the workpiece for aesthetic purposes or to increase the surface area, often used in heat sinks.

Wrapping Up

In conclusion, the right selection of a lathe cutting tool can significantly impact the quality, efficiency, and safety of your machining operations. Understanding the different types of lathe cutting tools and their functions can assist you in making more informed choices and enhance your work quality.

While this guide provides a comprehensive overview, remember that consultation with industry professionals or experienced machinists can be invaluable for effective tool selection, particularly for complex projects. Utilize their expertise and the information in this guide to take your lathe operations to the next level.

FAQ

Which cutting tools are used on a lathe?

Common lathe cutting tools include turning tools, parting tools, threading tools, knurling tools, and boring tools.

What is the strongest cutting tool?

Polycrystalline diamond (PCD) cutting tools are among the strongest and hardest. They’re used for high-precision machining of non-ferrous materials and can sustain high-speed cutting operations.

What is the hardest cutting tool?

Cubic boron nitride (CBN) and diamond tools are considered the hardest cutting tools, with diamond being the hardest known material. However, diamond tools can’t be used on steel due to carbon diffusion issues, so CBN is typically used for hard steel.

What speed do you cut steel on a lathe?

For high-speed steel tooling, cutting speeds might be between 30 and 50 feet per minute (fpm), while carbide tooling can handle around 150-200 fpm.