A lathe tool is a cutting tool with a single cutting part, used for turning operations. It is one of the most widely used tools in machining. The working part of the lathe tool is the section that generates and handles chips, including structural elements such as the cutting edge, features for breaking or curling chips, spaces for chip ejection or storage, and channels for cutting fluid.

The cutting part of the lathe tool consists of the main cutting edge, auxiliary cutting edge, rake face, main flank face, auxiliary flank face, and the tool nose angle. The methods of joining the cutting part to the shank (i.e., the clamping part) mainly include the integral type, brazed type, mechanically clamped type, and brazed-mechanically clamped type. Mechanically clamped lathe tools can avoid the stress and cracks generated in carbide inserts during high-temperature welding, and the tool holder can be reused multiple times. Mechanically clamped lathe tools generally use screws and pressure plates to clamp the insert. For mechanically clamped lathe tools equipped with indexable inserts, after the cutting edge becomes dull, it can be indexed to continue use, and the machine downtime for tool changing is short, hence they have developed rapidly.

Composition

The cutting part of the lathe tool is composed of the main cutting edge, auxiliary cutting edge, rake face, main flank face, and auxiliary flank face. Its geometric shape is determined by the rake angle γo, relief angle αo, principal cutting edge angle κr, inclination angle λs, auxiliary cutting edge angle κr', and tool nose radius rε. The selection of geometric parameters for a lathe tool is influenced by many factors and must be chosen according to the specific situation. The rake angle γo is selected based on the composition and strength of the workpiece material; when cutting materials with higher strength, a smaller value should be taken. For example, carbide lathe tools take a rake angle of 10° to 15° when cutting ordinary carbon steel; when cutting chrome-manganese steel or quenched steel, it is taken from -2° to -10°. Generally, the relief angle is taken as 6° to 10°. The principal cutting edge angle κr is determined based on the rigidity conditions of the process system, generally taken from 30° to 75°; when rigidity is poor, a larger value is taken. When turning stepped shafts, due to the requirements of the cutting method, an angle greater than or equal to 90° is taken.

Material

The tool nose radius rε and auxiliary cutting edge angle κr' are generally selected according to the required surface roughness of the machined surface. The inclination angle λs is determined based on the required chip flow direction and cutting edge strength. The form of the lathe tool's rake face is mainly determined by the properties of the workpiece material and the tool material. The simplest is the flat type; a flat form with a positive rake angle is suitable for high-speed steel lathe tools and carbide lathe tools used for finishing.

Classification

I. According to structure, they can be divided into solid lathe tools, brazed lathe tools, mechanically clamped lathe tools, indexable lathe tools, and form tools. Among them, the application of indexable lathe tools is increasingly widespread, and their proportion among lathe tools is gradually increasing.
II. Carbide Brazed Lathe Tools: The so-called brazed lathe tools.
III. Mechanically Clamped Lathe Tools: Mechanically clamped lathe tools use standard inserts and are lathe tools where the insert is held on the tool shank by mechanical clamping methods.

Parting Tools

Parting tools cut both narrow and deep grooves. The chip space is small, and chips are extremely prone to clogging. To reduce friction with the machined surface, both sides of their cutting part must be ground with auxiliary relief angles, which greatly weakens the strength at the root. Furthermore, when the parting tool cuts close to the workpiece center, the cutting speed approaches zero, which is unfavorable for cutting. Therefore, parting tools are very prone to "chipping" (breakage) during work. Advanced parting tools generally shape the main cutting edge into a herringbone pattern and grind the rake face into a roof shape, causing the chips to contract laterally and be discharged steadily in one direction, preventing clogging in the groove, while also making the bottom of the tool head convex to improve strength and rigidity.

Form Tools

Form tools are specialized tools for machining formed surfaces of revolving bodies. Their cutting edge shape is designed according to the workpiece profile and can be used on various lathes to machine the formed surfaces of internal and external revolving bodies. When machining parts with a form tool, the part surface can be formed in one pass, offering simple operation, high productivity, achievable tolerance grades of IT8 to IT10 and roughness of 10 to 5 μm after machining, and ensuring high interchangeability. However, form tools are more complex to manufacture, have higher costs, and the working length of the cutting edge is relatively wide, making them prone to vibration. Form tools are mainly used for machining medium and small-sized parts with formed surfaces in relatively large batches.

Types and Uses of Lathe Tools:

The lathe tool is the most widely used type of single-point cutting tool. It is also the foundation for learning and analyzing various types of cutting tools. Lathe tools are used on various lathes to machine external cylinders, internal holes, end faces, threads, grooves, etc. According to structure, lathe tools can be divided into solid lathe tools, brazed lathe tools, mechanically clamped lathe tools, indexable lathe tools, and form tools. Among them, the application of indexable lathe tools is increasingly widespread, and their proportion among lathe tools is gradually increasing.

I. Carbide Brazed Lathe Tool: The so-called brazed lathe tool refers to a tool where a pocket is machined on a carbon steel shank according to the required tool geometry angles, a carbide insert is brazed into the pocket using solder, and after grinding according to the selected geometric parameters, it is used.
II. Mechanically Clamped Lathe Tool: A mechanically clamped lathe tool is one that uses standard inserts and holds the insert on the tool shank by mechanical clamping methods. Such tools have the following characteristics:
(1) Due to increased tool life, usage time is longer, tool change time is shortened, improving production efficiency.
(2) The end of the pressure plate used to clamp the insert can serve as a chip breaker.
Characteristics of Mechanically Clamped Lathe Tools:
(1) The insert does not undergo high-temperature welding, avoiding defects such as decreased insert hardness and crack formation caused by welding, thus improving tool life.
(2) After the insert is reground, its size gradually decreases. To restore the insert's working position, the lathe tool structure often includes an adjustment mechanism for the insert to increase the number of regrinding times.
(3) The end of the pressure plate used to clamp the insert can serve as a chip breaker.
IV. Indexable Lathe Tool: An indexable lathe tool is a mechanically clamped lathe tool that uses indexable inserts. After one cutting edge becomes dull, it can be quickly indexed to an adjacent new cutting edge, allowing work to continue until all cutting edges on the insert are dull, at which point the insert is scrapped and recycled. After replacing with a new insert, the lathe tool can continue working.
III. Indexable Lathe Tool: An indexable lathe tool is a mechanically clamped lathe tool that uses indexable inserts.

1. Advantages of Indexable Tools: Compared with brazed lathe tools, indexable lathe tools have the following advantages:
   (1) High tool life because the insert avoids defects caused by the high temperatures of welding and grinding.
   (2) High production efficiency because machine operators no longer need to sharpen tools, greatly reducing auxiliary time such as machine downtime for tool changes.
   (3) Conducive to promoting new technologies and processes; indexable tools facilitate the promotion and use of new tool materials like coatings and ceramics.
   (4) Conducive to reducing tool costs; due to the long service life of the tool shank, the consumption and inventory of shanks are greatly reduced, simplifying tool management and lowering tool costs.

2. Clamping Characteristics and Requirements for Indexable Lathe Tool Inserts:
   (1) High positioning accuracy: After indexing the insert or replacing it with a new one, the change in the tool tip position should be within the accuracy tolerance of the workpiece.
   (2) Reliable insert clamping: Ensure close contact between the insert, tool seat, and tool shank contact surfaces, capable of withstanding impact and vibration, but the clamping force should not be excessive, stress distribution should be uniform, to avoid crushing the insert.
   (3) Smooth chip flow: There should be no obstructions on the rake face of the insert, ensuring smooth chip ejection and easy observation.
   (4) Ease of use: Changing the cutting edge and replacing the insert should be convenient and rapid. The structure should be compact for small-sized tools. While meeting the above requirements, the structure should be as simple as possible, easy to manufacture and use.
   IV. Characteristics and Requirements for Lathe Tool Inserts:
   (1) High positioning accuracy: After indexing the insert or replacing it with a new one, the change in the tool tip position should be within the accuracy tolerance of the workpiece.
   (2) Reliable insert clamping: Ensure close contact between the insert, tool seat, and tool shank contact surfaces, capable of withstanding impact and vibration, but the clamping force should not be excessive, stress distribution should be uniform, to avoid crushing the insert.
   (3) Smooth chip flow: There should be no obstructions on the rake face of the insert, ensuring smooth chip ejection and easy observation.
   (4) Ease of use: Changing the cutting edge and replacing the insert should be convenient and rapid. The structure should be compact for small-sized tools. While meeting the above requirements, the structure should be as simple as possible, easy to manufacture and use.