To make turned parts, a cutting tool is mounted on a lathe (wooden/handheld/CNC). They move along the lathe’s axis, and their path determines the final shape of the workpiece. There are several non-CNC lathes, and each type has unique features and designs that define the cutting operations and field applications supported by the lathe. Therefore, choosing the right cutting tool requires thorough knowledge. This article introduces popular lathe tools and their design, features, and applications. Let’s get down to business.
Four categories of turning tool types
Many types of cutting tools used on lathes or CNC lathes can be divided into four main categories: material, operation, design, and feed direction. Below are the various turning tools that fall into each category.
Class 1: Cutting tools based on lathe materials.
Many materials are suitable for making tools used on lathes, each of which has unique properties. Therefore, each cutting tool has properties based on the material’s mechanical properties. Below are typical lathe-cutting tools based on the material used.
Tool: High-speed steel (HSS)
High-speed steel contains elements such as tungsten, carbon, vanadium, and chromium. Cutting tools from this material are known for their extreme hardness, durability, and wear/heat resistance. In addition, they have high speeds suitable for roughing and semi-finishing machining.
Carbide tools:
Carbide
Carbide-turning tools are hard and brittle. Therefore, they are compatible with almost all materials. However, they are expensive, which limits their use in part production.
Diamond tool:
Turning tools made of diamonds are tough. Therefore, they are suitable for machining all materials. However, like carbide tools, they are expensive, which limits their industrial applications.
Regular boron nitride tools:
Cubic boron nitride
The next hardest is cubic boron nitride. They are durable, wear-resistant, and suitable for roughing and intermittent machining, especially when machining cast iron.
Class 2: Operation-dependent cutting tools of lathes
Turning tools are also classified according to machining operations. The following are typical tools used in each turning process.
-Turning tool: Turning tools remove material along the workpiece. This has the effect of reducing the diameter of the workpiece. There are two types:
– Rough turning tools: Rough turning tools are tools for removing large amounts of material from a workpiece in one go. That’s why they are often used to create neat shapes or to prepare surfaces for later finishing operations.
– Finishing turning tools: finishing turning tools are used to remove small amounts of material from the workpiece to produce a smooth finished surface.
-Chamfering tool: these turning tools are suitable for chamfering or creating chamfered edges. Turning tools are also ideal for chamfering. However, they must be at the right angle to the workpiece. In addition, they become obsolete when the bevel angle is large.
-Thread cutting tools: thread cutting tools help create spiral thread patterns on cylindrical parts. Usually, the angle of their corner depends on the expected thread angle. In addition, the cross-section of the tool affects the pitch.
-Facing tools: finishing tools use side cutting edges to remove thin layers of material and produce a smooth surface.
-Methods for forming tools: a forming tool combines turning and grooving tools to create complex shapes in a single pass. While turning tools can do the same job, molding tools are ideal because they increase accuracy and reduce cycle time.
-Grooving tool: these tools are used to turn grooves into parts with cylindrical surfaces. Several groove shapes are depending on the shape of the lathe. V-shaped and square cutters are common.
-Boring bar; dull tool: a boring bar is a cutting tool characterized by a boring bar with a cutting tool at the end. Therefore, it is used for machining and increasing the diameter of holes.
-Nursing tool: knurling tools have two or more metal rollers with an embossed pattern. They are often used to make indentations in workpieces to increase their adhesion.
Class 3: Structural cutting tools for lathes
According to their structure, lathe tools are mainly divided into three types. These are:
Single tools
They come from a single piece of material and have a specific shape, size and geometry. Therefore, they are the most commonly used lathe tools because of their speed and durability.
Welding lathe cutting tools
Welding lathe tool: the heads and shanks of these tools are made of different materials and joined together by welding. Typically, the sides are made of a material such as carbide, known for its strength and durability, while the body can be made of different metals. Because of the material differences, they provide less cutting power than monolithic tools.
Lathe clamping tools
The material composition of these cutting tools is similar to welding tools. However, instead of a welding tool, a clamped lathe tool is created by placing the insert (i.e., the cutting tool) on the handlebar. In general, clamped turning tools are flexible and interchangeable. Therefore, their properties, such as strength and durability, depending on the insert type.
Class 4: Lathe cutting tools classified according to to feed direction.
According to the feed direction, lathe tools are mainly divided into three types. These are:
Tool based on feed direction
Right-hand turning lathe cutting tools remove the material as they move from right to left. They have a structure similar to the human hand. This is because the right thumb points in the direction of feed, and the leading cutting edge is on the left side of the tool.
Cutting tools for left-handed lathes
These tools remove material while moving from left to right. According to the design of the human hand, the left thumb points in the direction of feed, and the main cutting edge is on the right side of the tool.
Cutting tool for circular lathes
These tools can move from left to right or right to left, as they do not have rotation angles and circles. They are suitable for machining where a smooth surface is required.
Note: There are other turning tools for different applications. It would help if you talked to a professional CNC machinist.
How to choose the right lathe tool?
We all know that good work requires the right tools. Choosing the right lathe cutting tool is very important for getting accurate results on the workpiece. Here is a list of ways to choose the right cutting tool for your lathe:
Lathe tool coating
Coatings are materials used on the outside of cutting tools to enhance their mechanical properties and aesthetics. They are also important because coated turning tools are more durable than uncoated tools. As you might expect, there are a number of coatings, including titanium nitride (TiN), titanium carbide (TiC), and aluminum oxide, each with its properties.
Workpiece material
The mechanical properties of the workpiece play a huge role in selecting the right cutting tool for the lathe. The most basic selection process depends on hardness, as hard materials can only be turned with hard or uncoated tools. This will prevent the tool from chipping during machining. For example, diamond and boron nitride tools are known for their strength and suitability for machining hard materials.
Required type of turning operation
Each turning operation requires a specific set of skills and tools. So make sure you choose the right tool for the operation. For example, turning tools are used to remove material along the workpiece. However, they are not suitable for forming processes. Another consideration is the direction of cutting.
The required shape of the part
The tool’s shape and part must also be considered when choosing a tool. For example, in turning operations, we can use rectangular turning tools to give the material a cubic shape.
Lathe tool assembly
Although the functions and applications of lathes have different designs, they all have some standard parts. Below are the parts common to each lathe.
Parts of lathe tools:
- Dry-This part is attached to the lathe. It is the thickest part of the tool and is mostly rectangular in cross-section
- Face-This is the part of the lathe’s cutting tool where the chips flow during turning operations
- Wing-This is the part that opposes and interacts with the workpiece. It can be larger or smaller and forms a cutting edge with the side of the cutting tool.
- Pioneer novel-this part is responsible for the cutting action of the tool. The cutting edge depends on the tool. For example, a single-point tool will have two cutting edges and may use two cutting surfaces.
- The blade of the knife-it is the main and side cutting edges. Its curvature adds strength, durability, and the ability to make smoother cuts.
- The front angle is the tool surface and a line perpendicular to the body. It determines the direction of chip flow.
- Lateral relief angle- viewed from the front, the lateral relief angle is the angle formed by the main shank with the shank surface perpendicular to the base of the cutting tool. It prevents the central shank from rubbing against the workpiece.
- Final relief angle- viewed from the side, it is the angle formed by the leading edge of the mandrel with the line normal to the tool base. It prevents the smaller side from rubbing against the workpiece.
- The back rake angle-is the angle between the face and the plane parallel to the base. A large rake angle increases sharpness but decreases strength and vice versa.
- Final cutting edge angle-This is the angle formed by the final cutting edge with a line perpendicular to the tool body and tangent to the nose. It prevents the tool from touching the workpiece surface.
- The angle of the lateral cutting edge- the angle that the lateral cutting edge forms with a line parallel to the tool body. Therefore, it plays a vital role in cutting force and chip thickness during turning operations.
Cutting tool operations-operations for turning tools
Available cutting tool operations for a lathe-The lathe can perform various machine operations. Below are the most common cutting tool operations that can be performed on a workpiece.
Turning
It is the most common cutting tool operation in machining. It involves creating a cylindrical part with precise geometry by removing excess material from the workpiece. Generally speaking, this operation can be automated in the case of CNC turning or manual, as in the case of other turning operations.
Facing operation
This cutting operation involves reducing the length of the workpiece to form the desired parts. It consists in using a cutting tool to cut off the piece perpendicularly.
Chamfering operation
It involves creating a beveled surface on the cylindrical edge of a workpiece. It has applications in reducing damage to sharp edges.
Knurling operation
Milling involves using two or more metal rolling wheels to create embossed patterns on a cylindrical workpiece. Therefore, it has applications in increasing the grips of a product.
Application
Lathe cutters are critical tools in CNC machining. They come in different types, which determines their performance and functions. As a result, choosing the right tool is essential for a successful machining operation.