Cutting tools
What are cutting tools?
Cutting tools are essential in various machining processes where they remove material from a workpiece by creating chips. Cutting tools are used to machine components like valves, cylinders, gears, molds, and other parts. Commonly, cutting tools are utilized in milling, turning, drilling, threading, shaping, and grinding. The main objective when using cutting tools is to achieve the most accurate and high-quality finished surface with minimal load and maximum tool life.
Tools used in turning
During turning, the workpiece rotates while the tool moves in a feed motion, removing material. Turning processes include face turning, rough turning, finish turning, parting/grooving, and thread turning. Turning tools, such as external and internal tool holders with indexable inserts, are designed for different shapes, shoulders, grooves, threads, and for parting off the workpiece. Tools can be mounted using a shank or through the Capto system.
Tools used in milling
Milling cutters are highly versatile cutting tools that rotate and remove material by the feed motion. Common milling operations include face milling, side milling, plunge milling, slot milling, 3D surface milling, and chamfer milling. Milling tools are typically solid carbide end mills or milling cutter bodies with replaceable inserts. These tools are used for machining flat surfaces, grooves, and more complex shapes. Cutters with replaceable inserts are especially useful because worn inserts can be replaced without needing to replace the entire tool.
Tools for hole machining
In hole machining, either the workpiece or the tool rotates, and the operation follows the tool’s rotational axis. This category includes tools such as solid carbide drills, replaceable tip drills, U-drills, and reamers. Drilling is the most common hole machining method, but other methods like threading, countersinking, and reaming are also important. Replaceable tip drills and U-drills are particularly popular due to their versatility and efficiency.
Threading tools
In threading, either the workpiece or the tool rotates, and the feed movement occurs axially in proportion to the thread pitch. Threading uses either cutting or forming taps as well as thread mills. Forming taps create threads without cutting, producing stronger threads. Cutting taps remove material using the cutting profile. Thread mills are often used for larger and precision threads.
Tool materials and coatings
The material and coating of a cutting tool significantly affect its durability and performance. The most common tool materials are high-speed steel (HSS), HSCo, carbide, cermet, PCD, and CBN. Various coatings, such as CVD (Chemical Vapor Deposition) and PVD (Physical Vapor Deposition), improve a tool's wear resistance and toughness and prevent material from sticking to the tool. For example, Walter Tools' patented Tiger·tec® Gold multi-layer coating combines the best qualities of several coatings and can extend tool life by up to 30–50%.
Cutting tool geometry
The geometry of a cutting tool and chipbreaker are key factors in tool performance and chip control. Light-cutting tools with positive rake inserts are best for finishing and applications prone to vibration, such as when using a long tool holder. Negative rake geometry is more durable than positive rake but also produces heavier cutting action. Different parts of the tool, such as the shank, cutting edge, flank face, side clearance, side edge, and rake face, create critical tool angles like relief angle, clearance angle, point angle, rake angle, setting angle, lead angle, and inclination angle.
Tool selection
Choosing the right cutting tool is a critical factor in the success of a machining process. The choice depends on factors like the machine tool used, workpiece material, machining method, tool holder, workpiece clamping, coolant, batch size, and automation level. Optimal tool selection helps reduce vibration, extend tool life, and increase productivity. For example, softer materials like aluminum require different tools than harder materials like steel or titanium.
Summary
Cutting tools are essential in manufacturing complex and precise parts in metalworking. Understanding tool selection, materials, coatings, and geometry can improve machining efficiency and quality. For a successful machining process, it's crucial to choose the right tool for the material and process to achieve optimal performance and long tool life.
