A Guide to Lathe Cutting Tools and the Selection Process

The lathe is called the king of the machine tools, and deservedly so – it is one of the most versatile machines in any workshop. But how well it works depends a lot on what cutting tools you use for it. This guide explores the different categories of lathe-cutting tools and how to select the most appropriate ones for your specific needs.

The composition of cutting tool materials affects their performance and longevity. High-speed steel (HSS) remains popular due to its general-purpose application and affordability, making it ideal for general-purpose use and small workshops. Carbide tools are more expensive but offer greater hardness and heat resistance. They are essential for production facilities working with harder materials. Ceramic tools work well in high-speed operations but are fragile and must be used with care. For extremely fine cutting, cubic boron nitride (CBN) and polycrystalline diamond (PCD) tools offer excellent performance but come at greater price points.

The foundation of any lathe tool set starts with basic turning tools. The right-hand turning tool is probably the most accommodating, utilized for external turning operations from right to left. Left-hand turning tools perform the same functions but from left to right. Neutral turning tools can be turned in either direction and are particularly well-suited for facing operations. When selecting these tools, pay attention to the approach angle of the tool, which affects both finishing quality and tool strength.

Facing tools are used for working on end faces of workpieces to produce flat surfaces at right angles to the axis of the workpiece. These tools typically possess a broad nose and operate from the outside towards the center. Parting tools or grooving tools are applied for creating grooves or separating parts entirely. They are narrow in shape and require maximum speed and feed rates to prevent binding. If you need this type of durable and ergonomic lathe cutting tools, observe the width of the groove needed and the depth of cut required.

Threading tools can be both external and internal, each capable of creating certain thread profiles. Single-point threading tools are versatile but must be applied with proficiency. Thread chasers and die heads offer faster production but lower flexibility. In selecting threading tools, apply the tool’s profile to your required thread standard (metric, imperial, acme, etc.) and consider the material being cut. Carbide-tipped threading tools offer greater wear resistance for production purposes.

Internal work requires boring tools, which come in various lengths and arrangements. Solid boring bars are appropriate for small bores, while insert-type boring tools are more adaptable for large bores. Anti-vibration boring bars contain dampening characteristics for high-reach operations. When selecting boring tools, consider the minimum bore diameter, depth needed, and clearance needed. The length-to-diameter ratio is extremely critical – greater than 4:1 without specialized equipment can lead to chatter and a poor surface finish.

Form tools are shaped to create specific profiles in one setup, i.e., radii, chamfers, or unique shapes. While such tools will cut significant time in production environments, they use more power and have stiffer setup equipment. In selecting form tools, consider whether the quantity of production is worth the expenditure for a custom tool versus using several standard tools to create the same profile.

Modern lathe cutting tools often utilize indexable inserts, which have multiple cutting edges and can be quickly replaced when worn out. When selecting inserts, consider the following factors:

• Chip breaker geometry, which affects chip control and surface finish

• Nose radius, which affects finishing capacity and tool strength

• Type of coating, which affects wear resistance and cutting temperature

• Grade, which balances hardness against toughness for specific applications.

Keeping your cutting tools for lathe in good condition has a big effect on performance and longevity. Store house tools in a dry location to prevent rusting and protect the cutting edges from potential damage. Regular inspections for wear and damage can prevent costly mistakes and workpiece damage. On insert-type tools, use proper torque when installing inserts and thoroughly clean mounting surfaces.

When making your final tool selection, consider your specific application requirements: workpiece material, surface finish requirements, tolerance specifications, and production volume. Factor in your machine’s capabilities, including power, rigidity, and speed range. Consider your budget not just for initial purchase but also for ongoing insert or replacement costs. Sometimes, a more expensive tool can prove more economical through longer life and better performance.

Selecting the right lathe cutting tools is a balancing act among various factors, including the material, operation type, machine capability, and economics. While this information is a starting point for selection, experience is invaluable. Start with basic, general-purpose tools and add to your inventory as you develop a clearer sense of your own requirements. Keep in mind that precise use and maintenance of even simple tools generally yields better work than misused high-priced tools.