Lathe-Cutting Tools: A Comprehensive Guide

Over the years, lathe-cutting tools have become life-saving equipment in various industries. Whether you operate these tools or want to procure one for your facility, this guide will show you everything you need to know about them. Read on!

What Are Cutting Lathe Tools?

Lathe-cutting tools or turning tools are special tools we use to drill or knurl a workpiece during machining. These tools have different shapes, textures, forms, and materials that contribute to producing excellent fabrications or finishes.

Also, the shapes and forms of these lathe-cutting tools determine how we use them during machining. This also makes each tool unique. For instance, we use chamfering tools with 45-degree angles or cylindrical radii to drill press or machine the center of a workpiece. The point is that we can only use this tool with such a structure for that purpose or operation.

Classification of Lathe-Cutting Tools

Lathe cutting tools come in different shapes, sizes, and forms, making it complex to determine them outright. However, every lathe-cutting tool falls under one of the following categories, which we will explain in this section. 

By knowing the classification of lathe-cutting tools, it becomes easier to determine which lathe-cutting or turning tool is which in the factory.

Class 1. Lathe-Cutting Tools Based on Material

During fabrication, we machine various metals and non-metals. However, the varying mechanical and chemical characteristics of these workpieces necessitate different cutting tools.

For this reason, we’d need tools derived from certain materials to turn or finish these workpieces excellently. For instance, carbide lathe-cutting tools are best suited for higher speeds and temperatures because they withstand them better.

Some of the lathe-cutting tools we categorize based on material types include high-speed steel, carbide tools, diamond, ceramic, and cubic boron nitride. Let’s see more on them below:

High-Speed Steel (HSS)

High-speed steel lathe-cutting tools were introduced in the late 1940s to replace the high-carbon steel. The upgrade in HSS’s chemical makeup allows it to cut and turn a workpiece faster and more efficiently than high-carbon steel. This is also why we call it a “high-speed steel lathe-cutting tool set.”

Additionally, this steel upgrade contributes to HSS’s toughness and ability to withstand high temperatures without deforming—a property it gets from the various alloys that make up its composition. 

For instance, the general formula for making HSS is Fe-C-x. Where Fe and C are the primary components of the HSS steel. On the other hand, x may represent Tungsten, Vanadium, Molybdenum, Cobalt, or a pair of these elements.

These x-elements give HSS more characteristic toughness and temperature resistance. Plus, they will be useful to you when finalizing which HSS tool you need.

Carbide Cutters

Generally, carbide tools or cutters have a steel body or removable blades with edges brazed with carbide. This carbide tipping helps them to produce excellent surface finishes and not wear off with steady machining.

Regarding longevity, carbide-cutting tools for lathes can arguably last about 99 times longer than high-speed steel tools. This is because they can maintain a sharp or harder cutting edge regardless of the temperature or speed of the machining. We further classify them into carbide-tipped tools and cemented carbide inserts.

Carbide-tipped tools are usually fixed or holistic. You may need to change the entire cutter or blade after it becomes blunt. On the other hand, you can rotate the cemented carbide inserts when one part is worn, thereby maintaining its size and quality finish longer.

Cubic Boron Nitride (CBN)

A cubic boron nitride, also called CBN nanopowder, is arguably one of the strongest materials on earth—second to diamond. When used to make lathe-cutting tools, it can cut or finish metals or metallic alloys at high speeds without requiring any cooling process in between or afterward.

The reason for this high-speed cutting is CBN’s inertness to carbon or any alloy with carbon. Additionally, CBN is more heat resistant than carbide and high-speed steel cutters combined. Amazingly, it is more heat resistant than diamond cutters too.

This speed and efficiency in turning or cutting steel and workpiece materials during fabrication reduces the fabrication cost by about 60%. You can confirm this estimate by calculating the overall machining cost alongside the tool’s cost.

Diamond Lathe Tool

Diamond lathe-cutting tools are the greatest lathe-cutting tools for high-precision cutting and finishing. Usually, we feature them as single-point cutting tools because of the cost and availability of diamonds. This single-point nature is the reason for its common name, single-point diamond turning (SPDT) or single crystal diamond cutting (SCDC) tool.

Generally, we affix the diamond in SPDT at the functional areas of the tool through bonding or welding. 

Ceramic Lathe Tool

One of the reasons we use ceramic lathe-cutting tools is their chemical stability and ability to give off rough and fine finishes. Plus, they are very heat resistant and do not wear easily. 

Like CBN, ceramic lathe tools can cut harder materials at high cutting speeds and feed rates without any coolants. A common type is the ceramic insert turning tool. We usually screwed this type into a tool holder. Like cemented carbide inserts, we rotate the sides to maintain the tool’s finishing quality longer.

Class 2. Lathe-Cutting Tools Based on Operation

Another way to recognize lathe-cutting tools in CNC lathe-cutting tools factories is by what we can do or achieve with them. Some of the lathe tools we categorize by their operation include turning, thread-cutting, chamfering, forming, facing, boring, grooving, and knurling tools.

Turning Tools

Turning is one of the most common machining operations in many fabrication factories. It’s simply a process used to remove excess material from a workpiece. This could be a rough turning operation where you remove excess materials to reveal the workpiece’s first view. Then again, it could be a fine-turning operation that produces an excellent sheared product and finishing.

Sometimes, we call lathe-cutting tools turning tools because they all undergo similar primary operations. Let’s say that “turning tool” is the generic lathe tools name. Nonetheless, other tools have some uniqueness, giving them their properties and names. For example, a thread-cutting tool produces thread-like objects like screws or bolts. 

Thread Cutting Tools

A lathe thread-cutting tool is usually edged with carbide or high-speed steel and used to make thread-like apertures in the internal or external surfaces of workpieces. This is usually a finishing operation after turning or boring a cylindrical workpiece.

Common tools used for this operation include screw tabs or thread-cutting dies. Large-scale or branded production companies may use a cold or hot forging process that capitalizes on the temperature differences of a workpiece material to strengthen its properties.

Thread-cutting dies are examples of lathe tools for metals. On the other hand, the screw tabs may act as a wood lathe tool or thread tool for lathe materials like glass or plastics.

Chamfering Tools

We use a chamfering cutting tool to smoothen surfaces or remove burrs or sharp edges from a workpiece. This process is called chamfering because the deburred material and form tool assumes the position of a chamfer or bevel at 45-degree angles. Chamfering makes the resulting material safer to hold and manipulate during other machining processes.

Form Tools

A form-cutting lathe tool is another common tool we use to fabricate or weld materials. As the name implies, you can use form tools to forge or design workpieces into desired designs or shapes you need. Other common activities we use form tools for include turning, presswork, and stamping.

Facing Tools

A facing tool is a turning tool we use to finish workpieces. They are usually coated with carbide, CBN, or HSS and give off fine finishes. Concerning architecture, facing tools are mounted perpendicularly to the rotating workpiece. The relief angles prevent other parts of the facing tool from interfering with the workpiece or machining process.

Boring Tools

Boring tools are single-point cutting tools used to elaborate an existing opening in a workpiece. With them, you can create a conical or cylindrical workpiece or finish an existing one. Their parts include a boring bit or tip, an arbor, and a boring bar (shank) that fits into a tool holder.

Grooving Tools 

With grooving tools, you make furrows inside or outside a cylindrical workpiece. Depending on the tool configuration, you could make thinner or wider grooves or furrows on workpiece surfaces. 

Furthermore, making these furrows requires high precision and accuracy, so we use grooving tools for CNC turning machining processes rather than manual machining.

Knurling Tools

Knurling tools are used to insert criss-cross patterns on a workpiece. After knurling, you can hold the material better as there is increased friction between the holder and the material.

Also, we can use knurling tools to repair originally knurled and faded materials. The architecture of a knurling tool is a pattern of crossed, straight, or angled lines, which, when used to machine a workpiece, gives it characteristic knurls or knots.

Class 3. Lathe-Cutting Tools Based on Structure

The third way to identify cutting tools is by their structure. Usually, these tools may come in a single holistic form or combine different materials in one tool. They include single-body tools, clamped tools, and welded tools.

Single Body Tools

A single-body tool, just like its name, has all its parts in one piece. This means their edge-cutting parts, tool angles, shank or bar, and every other essential lathe-cutting tool part are in one file. 

Nevertheless, machinists could adjust the single-body tools’ shape, size, or architecture depending on the need or intended product. Examples are some lathe-cutting tools for brass.

Clamped Tools

These tools are usually replaceable or upgradeable. They include inserts of tools, usually with multiple cutting edges screwed or clamped onto a shank to form a whole piece. Examples are cemented carbide insert tools.

Welded Tools

These tools have different end and side-cutting edges or parts welded or soldered together. This could enhance the lathe-cutting tool’s turning or finishing quality. Many boring and grooving tools fall into this category.

Class 4. Lathe-Cutting Tools Based on Feed Direction

Another class of lathe or turning tools are those with different feed directions. To be clear, a feed direction is the position of the cutting edges inserted into the turret or tool holder during machining. Or the part of the cutting edge that performs the machining or finishing on a workpiece.

Right-Hand Turning Tools

These tools move toward the chuck from right to left when machining. In this setup, the chuck holds the workpiece on the left side of the machine. Usually, you’d find the end cutting edge facing the left side and the relief angle facing the workpiece on the right. 

Left Hand Turning Tools

As the name implies, the left-hand metal lathe tool removes or cuts off chips while moving from left to right. In this case, the workpiece is on the right side of the machine. Also, the end or main cutting edge angle faces the right side.

Round Nose Lathe Tools

These tools are also called center lathe-cutting tools. They may have equal angles of 45 degrees on the left and right hands of the main cutting edges. You may or may not find rake angles. Examples are chamfering tools used to make smooth surfaces.

Components of a Lathe-Cutting Tool

Now that we’ve established the above concepts, let’s also look at the mechanical makeup or parts of lathe-cutting tools with which they produce quality machining.

Shank

Different lathe tooling experts may call shank different names. Some would say a shank is where a lathe tool connects to the holder. Others would argue that a shank is the body of a lathe-cutting tool.

Either way, the definitions point to the same meaning. You should know that the area of a lathe tool without any special styling or face for machining is the shank. It could be its body or handle. Usually, shanks maintain their positions in a tool holder through friction.

Cutting Edge

We also call the cutting edge the tool lips. Usually, we braze this part of the lathe-cutting tool with diamond, carbide, graphite, CBN, etc., coating. They are the points that shape or turn the workpiece material or remove chips during machining. 

As a rule of thumb, avoid burning the cutting edge of lathe tools to help them last longer. After each use, ensure you examine the edges and properly maintain them before the next use.

Face

The face is the part where the chips usually fall onto during machining. It’s intentionally curved or spaced to allow more chips to flow onto it before falling off so as not to cause clogging on the cutting edge.

Lathe-Cutting Tool Angles

Lathe tool angles are intentionally created to streamline machining. The three major angles include 

• Rake angles: Examples are the back and side rake angles. These angles hold or control the chips as the cutting lathe tool removes them from the workpiece. They help reduce the workpiece’s impact on the tool during machining.
• Relief angles: These parts work alongside the rake angles to maintain balance on the cutting tool. Relief angles are elevated to prevent the workpiece from rubbing with the cutting tool, hence giving a cleaner finish or cut and preventing the tool from wearing. We have the side and end relief angles that avoid rubbing in the longitudinal and lateral directions, respectively.
• The final angle is the cutting-edge angle: In single-point lathe tools, the cutting-edge position usually depends on the type and position of the workpiece. We have the end cutting edge (main cutting edge) angle and the side cutting edge (auxiliary cutting edge) angle. Both angles ensure that the workpiece is machine according to plan.

Nose or Cut-Off Point

This is the rounded part of the lathe-cutting tool where the main cutting edge meets the auxiliary cutting edge. It almost forms a right-angled triangle, only that the point of intersection is rounded to give it a nose radius. 

The nose radius gives us cleaner surface finishes and contributes to the cutting tool’s longevity.

Flank

Every single-point lathe-cutting tool has two flanks. You could spot the first flank, a.k.a the major flank, adjacent to the side or auxiliary cutting edge. All the same, you should find the second or minor flank adjacent to the end or main cutting edge.

Heel

The heel is usually the rounded part that joins the flanks and the base of the lathe-cutting tool. You can easily see how their shape affects the overall lathe-cutting tools’ geometry and performance.

Factors to Consider Before Choosing Lathe-Cutting Tools

Creating quality fabrication and finishing begins with choosing the right lathe-cutting tools. Here are some things to note when selecting lathe-cutting tools for optimal performance and efficiency.

Lathe Tools Coating

One way to prevent quicker tool failure or help your lathe tools last longer is by coating them. Generally, for any material, coating is a sure way to prevent natural wear action or rust caused by humidity, water, or any natural chemical actions on the tool.

Secondly, the coating gives the lathe tools some mechanical advantages over forces that could deform them. Examples of such forces are heat and friction during machining. To sum it up, ensure you choose lathe tools with proper coating. Or even so, coat them yourself.

Contrary to popular opinion, coating isn’t all about using oil or acrylic paints on your material. It could also mean applying inert elements or compounds to lathe tools to avoid natural wear. Examples are cubic boron nitride or carbide.

Cutting Speed and Feed Rate

Cutting speed and feed rate are other important factors because we cannot cut or finish all materials at the same speed. Usually, this depends on the type of material you’re working with.

For instance, harder or thicker materials require more torque or force from the rotary machine to give a fine cut. This translates as a lower speed or feed rate because the rotary tool tends to slow down when it comes in contact with a hard or thick material. Conversely, materials with lesser diameters or hardness cut very well at faster speeds.

So, it’s important to consider the type of material you’re cutting or turning to help you determine the speed or feed rate you’ll need. Not only speed or feed rate but also the complementing lathe-cutting tool to do the job.

The Workpiece and Type of Material Used for the Tool

Before you settle for a lathe tool for machining, take note of the workpiece material being machined. As a general rule of thumb, your lathe-cutting tool must be tougher than the workpiece material.

Fortunately, we can measure this hardness using a Brinell hardness tester. The other method is using industry-standard alloys or materials like carbide-tipped cutters or cemented inserts, diamond or CBN cutters, etc., to cut or finish corresponding workpieces.

The Type of Finish You Need

Besides the workpiece materials used during machining, you should also consider the type of finish you need. This could be a turning, cutting, knurling, facing, or shaping operation. 

Whatever the operation, there is always a corresponding lathe-cutting or turning tool that complements it. Typically, we say that lathe machining is versatile. Nevertheless, it’s the lathe-cutting tools that make it so. 

For this reason, you’d often find different cutting tools for lathe in various shapes, sizes, forms, appearances, etc. Each characteristic was intentionally created to facilitate quality machining of workpieces in the shape and operation you want.

Ensure you understand what you want in the workpiece before deciding to use or buy lathe-cutting tools.

The Type of the Lathe Machine

Finally, you should consider the type of lathe machine you’re working with. We have two types of lathe tools machines: manual and automated CNC lathes. The type or shape of the lathe-cutting tool you may need would depend on this.

Although, the tools used in a CNC machine would be the same as those used in a manual machine. The difference, however, would lie in their shapes and sizes. A custom CNC machine may require different sizes of cutting tools that fit into the machine’s architecture. The same logic applies to the manually-controlled machines.

Comparison Guide: HSS vs. Carbide vs. Ceramic

To help you make a quick decision, here is a comparison of the most common lathe tool materials based on their properties and application scenarios.

Understanding Lathe Tool Geometry Basics

Selecting the right tool isn’t just about material; it’s about geometry.

• Positive Rake Angle: Best for soft materials (Aluminum, Copper) to reduce cutting force and prevent built-up edges.

• Negative Rake Angle: Best for hard materials (Steels, Cast Iron) and interrupted cuts, providing a stronger cutting edge.

Troubleshooting Common Lathe Cutting Issues

Even with the best tools, machining problems can occur. Here is a quick guide to diagnosing and fixing common lathe cutting issues.

1. Vibration and Chatter

• Symptoms: Loud noise, wave-like marks on the workpiece surface.

• Possible Causes: Tool overhang is too long, workpiece is not secure, or cutting speed is too high.

• Solution: Reduce the tool overhang (keep the shank close to the holder), increase the feed rate slightly, or check the center height.

2. Rapid Tool Wear

• Symptoms: The cutting edge becomes dull quickly, leading to poor dimensional accuracy.

• Possible Causes: Cutting speed is too high for the material, or lack of coolant.

• Solution: Switch to a harder tool material (e.g., from HSS to Carbide), reduce spindle speed, or apply adequate coolant.

3. Poor Surface Finish

• Symptoms: The surface feels rough or looks cloudy.

• Possible Causes: Feed rate is too high, or the tool nose radius is too small.

• Solution: Decrease the feed rate for the finishing pass, use a tool with a larger nose radius, or increase the cutting speed.

4. Built-Up Edge (BUE)

• Symptoms: Material welds to the cutting edge.

• Possible Causes: Cutting speed is too low, common with aluminum or stainless steel.

• Solution: Increase cutting speed, use a polished insert, or use a tool with a positive rake angle.

Frequently Asked Questions About Lathe Cutting Tools

1. What is the best lathe tool material for cutting stainless steel?
Cutting stainless steel requires tools that can withstand high heat and work hardening. Generally, PVD-coated Carbide inserts are the best choice because they offer a balance of hardness and toughness. For hardened stainless steel, Cubic Boron Nitride (CBN) is recommended. At HMaking, we ensure the right tool grade is selected to prevent rapid wear and ensure precision in your CNC parts.

2. How do I interpret the ISO codes on carbide turning inserts?
The ISO code (e.g., CNMG 432) tells you the insert’s specifications:

• C: Shape (Diamond 80°)

• N: Relief Angle (0° for negative)

• M: Tolerance Class

• G: Chipbreaker/Hole type

• 432: Represents size (1/2″ I.C.), thickness (3/16″), and nose radius (1/32″).
  Understanding these codes is crucial for ordering replacements or communicating your project requirements to a manufacturer.

3. Why is my lathe tool chattering or vibrating?
Chatter usually occurs due to lack of rigidity. Common causes include:

• Tool overhang: The tool sticks out too far from the holder.

• High speed: Running the spindle too fast for the setup.

• Workpiece clamping: The part is not held securely.
  Solution: Shorten the overhang, check the center height, or use a tool with a smaller nose radius to reduce cutting pressure.

4. What is the difference between roughing and finishing turning tools?

• Roughing Tools: Designed to remove large amounts of material quickly. They typically have a larger nose radius and are built to withstand heavy cutting forces but leave a rougher surface.

• Finishing Tools: Designed to take light cuts to achieve the final dimension and surface smoothness. They usually have a smaller nose radius and sharper edge.
  Successful fabrication requires using the correct tool for each stage.

5. How can I extend the life of my lathe cutting tools?
To maximize tool life and reduce production costs:

• Use Coolant: Ensure a steady flow of coolant to manage heat.

• Optimize Feeds & Speeds: Don’t run tools beyond their recommended parameters.

• Choose the Right Coating: Use coated inserts (like TiN or TiAlN) compatible with your workpiece material.

• Rigid Setup: Minimize vibration, which is the number one killer of carbide edges.

6. Does HMaking use custom lathe tools for CNC machining projects?
Yes. While standard tools cover 90% of operations, complex geometries sometimes require custom tooling. At HMaking, we evaluate your design files and, if necessary, utilize custom ground tools or specialized form tools to achieve the exact tolerances and profiles your project demands. You can request a quote to see how we optimize tooling for your parts.

Conclusion

The secret to producing quality finishes is picking the right cutting tool. Hopefully, this guide gives you every information you need to identify or make custom lathe-cutting tools that fulfill your machining needs regardless of the type of machine you use.

Nonetheless, you can navigate our resource center or product catalog for extra information about quality CNC machining, CNC parts, and products you may need in your fabrication factory. Moreover, you can request a quote or talk to our support if necessary.