Cutting Tools (Lathe Cutting Tools)

Types of Lathe Cutting Tools

1. Single-Point Cutting Tool (SPCT)

   • Description: A single-point cutting tool is commonly used in turning operations. It has a single active cutting edge, and is often made from HSS or carbide. These tools are primarily used for turning, facing, and other shaping operations on a lathe.
   • Applications: Used for cutting cylindrical parts, threading, and profiling.
   • Advantages: Offers high cutting efficiency and produces good surface finish when properly ground.

2. Double-Point Cutting Tool

   • Description: This tool has two cutting edges, allowing it to engage more material during the cutting process. It is typically used for heavier cuts or for turning large workpieces.
   • Applications: Used in applications requiring heavy cutting forces like roughing operations.
   • Advantages: Provides better tool life and performance when used in rough cutting conditions.

3. Parting and Grooving Tools

   • Description: These tools are designed for cutting off or creating grooves in the workpiece. Parting tools have a thin, straight edge that can separate parts of a workpiece, while grooving tools are used to create precise, narrow channels.
   • Applications: Common in applications requiring the separation of parts or the creation of grooves for o-rings, seals, or threads.
   • Advantages: Provide clean cuts with minimal material distortion and can be used on both small and large diameters.

4. Threading Tools

   • Description: Threading tools are specialized tools used to cut internal or external threads. These tools are precision-ground to specific thread profiles, such as metric, unified, or tapered threads.
   • Applications: Used in applications where precision threads are required, such as bolts, screws, and nuts.
   • Advantages: Provide high accuracy in the threading process, reducing the need for secondary operations.

5. Boring Tools

   • Description: Boring tools are used to enlarge holes or create precise internal diameters. They can be fitted with interchangeable inserts to adjust for various sizes.
   • Applications: Common in machining applications that require highly accurate internal dimensions, such as bores for bearing fits or sleeves.
   • Advantages: Offer precise diameter control and high surface finish.

6. Fly Cutting Tools

   • Description: Fly cutting tools are used to produce smooth, flat surfaces. They typically have a single cutting insert and rotate at high speeds.
   • Applications: Used in milling operations but also sometimes on lathes for finishing surfaces that require a smooth finish.
   • Advantages: Provides an excellent surface finish and is suitable for low-volume production runs.

Material Composition of Lathe Cutting Tools

1. High-Speed Steel (HSS):

   • Properties: HSS is known for its ability to retain hardness even at high temperatures. It is tough and resistant to wear, making it ideal for general machining operations.
   • Applications: Used for light to medium cutting tasks on a variety of materials.

2. Carbide Tools:

   • Properties: Carbide is much harder than HSS and can maintain a sharp cutting edge for longer periods, making it ideal for high-speed machining and harder materials.
   • Applications: Common in high-precision turning and machining operations, especially for metals like stainless steel, titanium, and other hard alloys.

3. Ceramic Tools:

   • Properties: Ceramic tools are harder than carbide and can withstand higher temperatures, but they tend to be brittle and are sensitive to shock loading.
   • Applications: Used for high-speed cutting of hard, tough materials such as cast iron and hardened steel.

4. Cermet Tools:

   • Properties: Cermet is a combination of ceramic and metal, offering high wear resistance and thermal stability while maintaining toughness.
   • Applications: Often used in finishing operations on hard materials like stainless steel.

5. CBN (Cubic Boron Nitride) and PCD (Polycrystalline Diamond) Tools:

   • Properties: These superhard materials offer exceptional wear resistance and are used for cutting very hard or abrasive materials.
   • Applications: CBN is used for hardened steels and cast irons, while PCD is ideal for non-ferrous materials like aluminum and composites.

Geometrical Features of Lathe Cutting Tools

Lathe cutting tools have several important geometric features that affect their cutting performance, such as:

1. Point Angle (or Cutting Angle): The angle at the tip of the tool. It is critical for controlling cutting forces, chip flow, and surface finish.

2. Rake Angle: The angle formed between the cutting face and the material being cut. A positive rake angle helps reduce cutting force, while a negative rake angle increases tool strength and durability.

3. Relief Angle: The angle that provides clearance between the tool and the workpiece, allowing the cutting edge to contact the material without dragging.

4. Nose Radius: The radius of the tool tip. A larger nose radius typically produces a better surface finish but requires higher cutting forces.

Cutting Conditions for Lathe Tools

The performance and life of lathe cutting tools depend heavily on cutting conditions, which include:

• Cutting Speed: The speed at which the cutting tool interacts with the material. It is typically measured in meters per minute (m/min).
• Feed Rate: The distance the tool moves during each cutting stroke. This is usually measured in millimeters per revolution (mm/rev).
• Depth of Cut: The thickness of the material removed in one pass of the cutting tool, typically measured in millimeters (mm).
• Coolant Use: Coolants help to dissipate heat, reduce friction, and extend tool life. They are particularly important when machining difficult-to-cut materials.

Conclusion

Lathe cutting tools are essential components in manufacturing and machining processes, each designed for specific operations like turning, facing, threading, and grooving. The choice of tool material, geometry, and cutting conditions can significantly affect machining performance, tool life, and the quality of the finished workpiece. Understanding the types of lathe cutting tools and how to optimize their use is critical to achieving efficient and precise machining operations.