Cutting tools

Material removal machining refers to the manufacturing of a workpiece through various machining processes that produce chips, such as milling, turning, drilling, threading, planing, grinding, or sawing. In material removal machining, the tool removes material from the workpiece by moving relative to it with a specific feed and machining motion, commonly referred to as machining. Machining typically produces parts and components for machines and equipment, such as valves, cylinders, or gears, and molds for manufacturing plastic products. Today, metalworking machines are mainly automatic, known as CNC (Computer Numerical Control) guided machine tools. Metalworking machines are generally categorized as either lathes or milling machines. Various types of lathes include the lathe, CNC lathe, vertical turret lathe, multitasking lathe, Swiss-style lathe, and so on. In terms of milling machines, there are manual mills, vertical machining centers, horizontal machining centers, longbed milling machines, portal milling machines, boring mills, etc. Modern CNC-controlled machines are commonly programmed using CAM software, which allows specifying machining methods, cutting tools, and machining parameters for an electronic drawing and generating a suitable NC code for machine control.

Cutting tools are generally classified into the following categories:

• Turning: A machining method where the workpiece rotates and the tool cuts material by moving with a feed motion. Various turning methods include face turning, rough and finish turning, plunge turning, turning with a parting tool, dynamic turning, thread turning, and PrimeTurning. Tools used in turning commonly include holders equipped with replaceable carbide inserts for external or internal turning, allowing for the turning of shoulders, forms, grooves, threads, and cutting off the workpiece. Turning toolholders can have either shank or Capto mounting.
• Milling: A machining method where the tool rotates and removes material with a feed motion. Milling can include face or shoulder milling, plunge milling, slot milling, dynamic milling, 3D surface milling, chamfer milling, etc. Tools commonly used in milling include solid carbide end mills or milling cutter bodies with indexable inserts, which can mill surfaces, shoulders, slots, and other shapes.
• Hole making: A machining method where either the workpiece or tool rotates, and machining occurs in the direction of the tool's rotation axis. Hole machining can involve drilling, threading, reaming, boring, or enlarging. Common tools for hole machining include solid carbide drills, point drills, indexable insert drills, and boring tools.
• Threading: A machining method where the workpiece or tool rotates, with the tool feed motion occurring in the direction of the tool's rotation axis in proportion to the thread's pitch. Threads can be made using a tap or forming tap or a thread mill.

Factors influencing the selection of the correct tool include the machining process, the available machine tool, the material being machined, the machining method, the tool holder, the workpiece clamping, the coolant, as well as batch size and automation level. Choosing the right tool helps in the success of the machining process by reducing vibrations, improving tool life, and increasing production efficiency using methods and machining parameters.

The material and coating of the cutting tool significantly impact the tool's durability and machining parameters with different machined materials. Different tool materials include, for example, high-speed steel (HSS), cobalt, carbide, cermet, ceramic, PCD, CBN. Cutting tools are available in various coatings with different properties, grouped into CVD (Chemical Vapor Deposition) and PVD (Physical Vapor Deposition) categories. Their purpose is to improve tool wear resistance, toughness, and prevent the material from adhering to the tool. Various cutting tool manufacturers offer several tool coatings based on these techniques and their combinations, such as Walter Tools' patented Tiger·tec® Gold multilayer coating. This allows tool life to be extended by up to 30-50%, with better resistance to notch wear and thermal cracks, improved insert toughness, and easier detection of tool wear. The Tiger·tec® Gold multilayer coating stands out from all other market coatings by combining the best properties of multiple coatings. At the bottom is the MT-TiCN coating, which reduces notch wear and increases insert toughness due to its multilayer structure. The Al2O3 coating layer increases resistance to thermal cracks in the insert, and the gold-colored surface layer facilitates the detection of insert wear.

The geometry of a cutting tool and its chipbreaker are crucial factors for tool functionality and chip control. A light-cutting tool with a positive insert is best suited for finish machining and vibration-prone areas, such as when using a long tool holder. Negative insert geometry is much more durable than positive inserts but also heavier to cut. The parts of a cutting tool include the tool shank, main cutting edge, clearance surface, secondary clearance surface, secondary edge, and rake surface. They form essential angles for the tool's function, such as the relief angle, cutting angle, tip angle, rake angle, setting angle, back angle, and lead angle.

Choosing the correct insert material, tool geometry, and coating is significantly influenced by the material being machined. Machined materials are categorized into the following groups, indicated by the following letter codes: P=Steel, M=Stainless steel, K=Cast iron, N=Non-ferrous metals, S=Superalloys and titanium, H=Hard materials, O=Non-ISO standard.

The wear of cutting tools must be monitored, and tools should be maintained regularly to achieve dimensionally accurate workpieces and meet surface quality requirements. Cutting tool wear can be identified by various wear types, such as notch wear, crater wear, plastic deformation, fractures, chipping, thermal cracks, and built-up edges. Indexable insert tools can have their inserts changed, and worn inserts can be recycled into new carbide blanks. Solid carbide rotating tools, such as drills and end mills, can be sharpened and recoated to their original geometry and coating by most tool manufacturers.

The true cost of tools is determined not only by the purchase price but also by productivity, i.e., the machining parameters used and tool life. Tool total cost can be influenced by servicing the tools to like-new condition. In Walter Tools’ resharpening service, products are reshaped according to original geometries and coated with Walter Tools' own coatings. The surfaces of resharpened products are polished to smoothness after coating, ensuring good chip evacuation along the cutting path. Products are then laser-marked and individually packaged before being returned to the customer. Resharpened products are delivered to the customer within about 4 weeks. Walter Tools also sharpens tools not originally manufactured by the company.

Today, tool automation systems have become more common for managing cutting tools. Tool cabinets reduce tool search time and the need for new tool orders, reducing employee workload. Automated cabinets can be fully customized to stock not only indexable inserts but also larger cutting tools like milling and turning cutter bodies and long drills. In the Walter Toolstation tool automation system, product databases can include extensive product-specific information, such as suitable insert screws and other spare parts details. Multiple suppliers can be defined in the system, and orders can be guided directly to their systems. Thanks to order limits, tool inventory levels can be set as low as possible, ensuring that company capital is not unnecessarily tied up in maintaining an excessively large tool inventory.