A cutting tool is a tool mounted on a lathe (wooden/manual/CNC) used for making turned elements. They move along the axis of the lathe, and their path determines the final shape of the machined object. There are several lathes other than CNC, and each type has unique features and designs that determine the cutting operations and field applications handled by the lathe. Therefore, choosing the right cutting tool requires a thorough knowledge of the tool. The turning knife can be made of austenitic alloys of non-ferrous metals, light alloys of heat-resistant materials, etc. Remember that the execution of the element should take place at both sufficiently high cutting speeds, moderate cutting speeds, and low cutting speeds. This article presents turning knives, cutting tools, and their design, properties, and applications. Let's get to the point.
Four categories of lathe tool types
Many types of cutting tools used on lathes or CNC lathes can be divided into four main categories: material, action, construction, and feed direction. Below are various lathe tools that belong to each category.
Class 1: Cutting tools based on materials for lathes
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 mechanical properties of the material. Below are typical lathe cutting tools depending on the material used.
Tool: High-Speed Steel (HSS)
High-speed steel contains elements such as tungsten, carbon, vanadium, and chromium. Cutting tools made from this material are known for their extreme hardness, durability, and resistance to wear/heat. In addition, they have high speeds suitable for rough and semi-finishing machining.
Tools made of cemented carbides:
- Carbide
- Turning tools made of cemented carbides are hard and brittle. Therefore, they are compatible with almost all materials. However, they are expensive, which limits their use in parts production.
Diamond tools:
- Diamond
- Diamond-made lathe tools are incredibly hard. Therefore, they are suitable for machining all materials. However, like tools made of cemented carbides, they are expensive, which limits their industrial applications.
Tools made of regular boron nitride:
- Cubic boron nitride
- The next hardest is cubic boron nitride. They are durable, resistant to wear and suitable for rough and interrupted machining, especially during cast iron processing.
Class 2: Lathe cutting tools dependent on operations
Lathe tools are also classified according to machining operations. Below are typical tools used in each turning operation.
-Lathe Tool: Lathe tools are used to remove material along the workpiece. As a result, this leads to a reduction in the diameter of the workpiece. There are two types:
– Roughing turning tools: Roughing turning tools are tools for removing large amounts of material from the workpiece at once. Therefore, they are often used to create sleek 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 in order to achieve a smooth finished surface.
-Chamfering tool: these lathe tools are suitable for chamfering, which is the creation of beveled edges. Lathe tools are also suitable for chamfering. However, they must be at the correct angle relative to the object being machined. Moreover, they become obsolete when the inclination angle is large.
-Thread cutting tool: thread cutting tools are useful for creating spiral thread patterns on cylindrical parts. Typically, the angle of their corners depends on the expected thread angle. Additionally, the cross-section of the tool affects the pitch.
-Facing tool: finishing tools use side cutting edges to remove thin layers of material and achieve a smooth surface.
-Tool forming methods: the tool forming combines turning and grooving tools to create complex shapes in one pass. While turning tools can do the same job, forming tools are ideal as they increase accuracy and shorten the cycle time.
-Grooving tool: these tools are used for grooving in elements with cylindrical surfaces. There are several shapes of grooves depending on the shape of the lathe. A common one is the V-shaped and square lathe knife. There are also hand-held lathe knives.
-Boring bar; boring tool: A boring tool is a cutting tool characterized by a boring head with a cutting tool at the end. Therefore, it is used for machining and increasing the diameter of holes.
-Knurling tool: Knurling tools have two or more metal rollers with an embossed pattern. They are often used to make indentations in the objects being machined 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 due to their speed and durability.
- Lathe welding cutting tools
Lathe welding tool: the heads and shanks of these tools are made of various materials and are joined together by welding. Typically, the sides are made of a material such as carbide, known for its strength and durability, while the body may be made of various metals. Due to the material differences, they provide less cutting force than monolithic tools.
- Lathe fastening 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 a plate (i.e., the cutting tool) on the handle. Generally speaking, clamping lathe tools are flexible and interchangeable. Therefore, their properties such as strength and durability depend on the type of plate.
Class 4: Cutting tools for lathes classified by feed direction
According to the feed direction, lathe tools are mainly divided into three types. These are:
Tool based on feed direction
Right-handed lathe cutting tools remove material while moving from right to left. They have a structure similar to a human hand. This is because the right thumb indicates the feed direction, and the main cutting edge is on the left side of the tool.
Left-handed lathe cutting tools
These tools remove material while moving from left to right. According to the design of the human hand, the left thumb indicates the direction of feed, and the main cutting edge is on the right side of the tool.
Lathe round cutting tool
These tools can move from left to right or from right to left, as they do not have rotation angles and wheels. They are suitable for machining where a smooth surface is required.
Note: There are other lathe tools for various applications. You should talk to a professional CNC mechanic.
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 achieving accurate results on the machined object. Here is a list of ways to choose the right lathe cutting tool:
- Lathe tool coating
Coatings are materials applied to the exterior of cutting tools to enhance their mechanical properties and aesthetics. They are also important because coated turning tools are more durable than uncoated ones. As one might expect, there are many types of coatings, including titanium nitride (TiN), titanium carbide (TiC), and aluminum oxide, each with its own properties.
- Working material
The mechanical properties of the workpiece play a huge role in selecting the appropriate 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 tools and boron nitride are known for their durability and usefulness in machining hard materials.
- Required type of turning operation
Each turning operation requires a specific set of skills and tools. Therefore, 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 operations. Another issue is the direction of cutting.
- Required shape of the part
When choosing a tool, the shape of the tool and parts should also be taken into account. For example, in turning operations, we can use rectangular turning tools when we want to give the material a cubic shape.
- Set of turning tools
Although the functions and applications of lathes have various designs, all have some common parts. Below are the parts common to every lathe.
Parts of lathe tools:
- Shank– this part is attached to the lathe. It is the thickest part of the tool and usually has a rectangular cross-section
- Face– this is the part of the lathe cutting tool where the chips flow down during the turning operation
- Wing - this is a part that opposes and interacts with the object being machined. It can be larger or smaller and forms a cutting edge with the side of the cutting tool.
- Pioneering innovative - 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 can use two surfaces for cutting.
- Knife blade - it is the main and secondary cut of the cutting edges. Its curvature adds strength, durability, and the ability to make smoother cuts.
- Front side angle - it is formed by the tool surface and the line perpendicular to the body. It determines the direction of chip flow.
- Side relief angle - looking from the front, the side relief angle is the angle formed by the main shank with the grip surface perpendicular to the base of the cutting tool. It prevents the main shank from rubbing against the object being machined.
- End relief angle - looking from the side, this is the angle formed by the front edge of the shank with the normal line to the base of the tool. It prevents the smaller side from rubbing against the object being machined.
- Back rake angle - is the angle between the front surface and a plane parallel to the base. A large back rake angle increases sharpness, but reduces durability and vice versa.
- End cutting edge angle - is the angle that the final cutting edge forms with a line perpendicular to the tool body and tangent to the nose. It prevents the tool from touching the surface of the object being machined.
- Side cutting edge angle - the angle formed by the side cutting edge with a line parallel to the tool body. Therefore, it plays an important role in the cutting force and chip thickness during turning operations.
Operations with cutting tools - operations on turning tools
Available operations of the cutting tool for a lathe - a lathe can perform various machining operations. Below are the most common operations of the cutting tool that can be performed on the workpiece.
Turning
It is the most common operation of a cutting tool in machining. It involves creating a cylindrical part with precise geometry by removing excess material from the machined object. Generally speaking, this operation can be automated in the case of CNC turning or manual, as in the case of other turning operations.
Face milling operation
This cutting operation involves reducing the length of the workpiece to form the desired parts. It involves using a cutting tool to perpendicularly cut off parts.
Chamfering operation
It involves creating a slanted surface on the cylindrical edge of an object. It is applicable in reducing damage to sharp edges.
Knurling operation
Milling involves using two or more rotating metal wheels to create embossed patterns on a cylindrical object. Therefore, it is applicable in increasing the grips of the product.
Conclusion
Lathe cutters are key tools in CNC machining. They come in various types, which determines their operation and functions. As a result, choosing the right tool is important for a successful machining operation. In difficult machining conditions, or when using high-speed steel, it is worth having the best lathe knife and cutting tools. The best tools will help during the machining of copper alloys, alloy steels, or manganese steel machining. Therefore, in significant cross-sections of the cutting layer, or medium chip cross-sections, a properly selected tool is so important.