In modern manufacturing, lathe-cutting operations are performed by automated Computer Numerical Control (CNC) systems. Here, a special tool rotates on an axis and applies pressure to a material that’s held by a spindle. Depending on the lathe operation, as you will learn in this article, there are many different types of lathe-cutting tools.
How Lathe Tools are Categorized
A lathe is defined as a machine that shapes various materials such as metal or wood by rotating them against a cutting tool. The term “cutting” generally means that the machine removes part of the material to achieve the desired shape. Therefore, almost all lathe operations can be considered as cutting operations.
There are many ways of creating the shape of a material. For this reason, lathe-cutting tools can be classified into various categories. Also, the classification is broadly created based on four critical aspects;
- According to operation
- Volgens materiaal
- According to structure
- According to the feed direction
From these four classes, we get various types of lathe-cutting tools for CNC machines. Let us explore the common tools and how they work.
Classification Based on Operation
This classification covers tools based on the sny operation being used. Some of the common tools that fall under this category include;
Turning is the most common operation of lathe machines. Tools used to achieve this operation move along the length of the spinning workpiece, removing part of it and thereby reducing its diameter. The outcome of the operation will depend on the angle of the workpiece, the speed, depth, and feed rate.
CNC turning tools can be divided further into two, depending on the operation being used;
- Rough turning tools – These turning tools have a specific angle that facilitates the removal of large chunks of material at a fast rate. As a result, these tools do not have to smooth-finish the material.
- Finish turning tools – These types of tuning tools are applied after the rough tool to remove small surface material and create a smooth finish. High-level precision is required to ensure that the workpiece is perfectly smooth.
In CNC machining, a chamfer is a transitional edge created by a special tool on two faces of an object. This edge is usually angled at 45°.
Chamfering tools are further classified based on the mechanism used to achieve the chamfer feature on the workpiece. The mechanism implied here describes the geometry used to achieve the chamfer.
The first classification describes the tools that create a single angle on the workpiece. In other words, the tip of the chamfer tool is angled such that the chamfering operation achieves a uniform angle across the entire edge of the workpiece.
Secondly, a chamfering tool can create variable angles on the workpiece. This is made possible by adjusting the angle of the chamfer tool during the machining operation. All these operations lead to chamfers with variable angles depending on the specifications of the machining requirements.
Shoulder Turning Tool
This is a rather complex operation that leads to the formation of bevels or fillets on the shoulder area of a workpiece. A shoulder can be any area of a workpiece depending on its shape, size, and geometry.
Tools used to achieve a shoulder can also be called shoulder milling tools. Shoulder turning tools have either a knife or side-cutting angle. This difference is there to account for the formation of either a beveled or filleted shoulder.
A shoulder can be squared, beveled, or filleted. Square shoulders are created by turning tools with a knife-edge while bevels and fillets are created by a straight turning tool. When creating fillets, the straight tuning tool has to have a nose radius to account for the concave or convex angle that is a feature of a fillet.
Thread Cutting Tool
As the name suggests, this tool is used to cut threads on a workpiece. Threads can be cut either on the internal or external part of the metal or wood material. This tool is essential since it makes it possible to create bolts and screws.
The internal thread is usually known as the female while the external is referred to as the male. This terminology is used to imply the mating of the threads. Like all other CNC lathe cutting tools, the thread cutting tool is put in an axis and the workpiece is rotated in a spindle.
This tool utilizes a side cutting edge to remove a cross-sectional area of a workpiece and create a smooth finish. To elaborate, the tool cuts a flat surface that is perpendicular to the rotational axis of the workpiece.
Facing tools are used in milling or machining operations. For machining operations, facing tools are used in boring or turning operations. This means that boring and turning tools can fall under the broad category of facing operations.
One advantage of using a facing tool with a CNC machine is that the CNC system feeds the workpiece at a constant feed rate. This has the benefit of producing a smoother surface. Still, you as the machinist have the option to make roughing or finishing cuts.
These tools are used to make paths or channels in a workpiece. Grooving is also known as a recessing operation.
The paths and channels created using grooving tools facilitate the mating of joining parts. Given that there are various types of fits formed during joining, these grooving tools exist in many different types. If you start getting technical, you could classify some turning, boring, and facing tools as grooving tools.
The two major types of grooving tools are inner and outer diameter tools. Inner diameter grooving tools create a groove on the surface of the workpiece while other one creates the same grooves on the inner surface of the workpiece.
This tool is special because it combines turning and grooving operations in one tool. This can result in the formation of complex designs that would be impossible or challenging to achieve with one or the other tool. This tool is not widely used since its applications are limited. However, it comes in handy when the design calls for it.
This tool is among the most straightforward in this category. The term boring refers to an operation where the machine expands the diameter of the feedstock gradually. The boring tool is usually inserted into an existing hole and it expands it.
The boring tool leaves a cylindrical opening that has a larger diameter than the previous opening. Boring operations are different from turning in that a boring tool is a single-piece tool.
Classification Based on Material
CNC cutting tools can also be classified based on the material they are made of. Some of the common tools in this category are made of the following materials;
Carbide is a material that is made up of carbon and a metal compound. It has features such as wear resistance and high thermal stability. For these reasons, carbide is a highly sought-after material for making CNC cutting tools.
Due to the high wear resistance of carbide, lathe-cutting tools made from this material can achieve high-speed cutting and precision cuts. Moreover, carbide can be used for cutting workpieces of high-resistant steel, cast iron, glass, and plastics.
This is an alloy of regular steel that is reinforced with several additives to make it suitable for cutting other materials. High-speed steel has a high wear resistance, toughness, and thermal strength. The combination of these features makes high-speed steel ideal for cutting other metals.
High-speed steel can be reinforced further with either molybdenum or cobalt. This gives us two types of HSS; that is molybdenum high-speed steel and cobalt high-speed steel. These two types of HSS can be used to machine-cut various materials, regardless of their strength.
As one of the hardest natural materials, it only makes sense for it to be used as a lathe machining tool. Its hardness ensures that it can cut into various materials, including metals, glass, and wood without wearing out easily.
The most common type of diamond used for making CNC lathe tools is known as Polycrystalline Diamond (PCD). This is a synthetic diamond that has high abrasion resistance due to the addition of alloying elements such as ceramic that are added during the forming process.
One of the disadvantages of diamonds is that it is extremely costly. This leads to low accessibility for machinists with limited budgets. On the plus side, your customers are constantly looking for this tool to cut hard materials such as ceramics and glass.
Special coated tools
During machining operations, a phenomenon known as chip adherence can occur. This is characterized by the extrusion and fraction between the machining tool and the surface of the workpiece. This phenomenon occurs when or if the tool has a high affinity to elements such as iron. To solve this problem, specially coated tools are normally used.
Cubic Boron Nitride (CBN) is one of these coating materials that are used to coat machining tools and help avoid this problem. CBN is known to have a high hardness that is slightly lower than that of diamond, but it has quite high thermal stability.
Classification based on structure
Lathe-cutting tools can also be classified based on their structure or form. This classification gives us three types of lathe tools, namely;
Single body type
These types of tools have a uniform material making up the whole structure of the tool. For instance, you will find a turning tool made up entirely of ceramic or high-speed steel. These tools are strong enough to be used for general CNC machining operations.
For these types, you will find that they have a clamp where different chips can be attached. In other words, they have an interchangeable mechanism where you can use multiple sub-tools in one. Think of the drill bit and the drill machine. This flexibility increases the accessibility of the tools which in turn increases its productivity and value.
In instances where you need to modify a lathe tool or create custom ones, welding can be the most suitable solution. It allows you to create intricate geometries that you can use for various lathe operations. The benefit of welding tools is that they are easily accessible and the customization options are endless.
Classification based on feed direction or speed
Feed direction and speed are also used as aspects to classify lathe-cutting tools for CNC machines. In this category, you will typically come across the following types of tools.
These tools remove/cut the undesired material from right to left. This is the most common feed direction used for CNC machining. Besides, the majority of the lathe machines have a right-left orientation. This tool cuts material by moving leftward.
A left-hand tool is the complete opposite of a right-hand tool. It removes material from the workpiece by moving in the right direction. It is not common to find CNC lathe machines that have a left-hand tool attachment. However, some are in the industry.
Round Nose Tool
These tools can cut in either the right or left direction. This is because they do not have side and back rake angles which are essential in determining the direction of the feed. On the positive side, this means that the tool is versatile for use in multiple orientations.
CNC machines offer a high level of precision and speed compared to manual operations. This is reflected in the volume of machined parts and the revenue generated by machinists who use CNC systems. The tools discussed in this article have helped you identify some of the common lathe-cutting tools you expect to find in the industry.