During the metal cutting process, turning tools inevitably wear due to intense friction with the workpiece and chips, as well as high temperatures. This wear not only affects machining accuracy and surface quality, but also reduces production efficiency and increases production costs. There are various forms of turning tool wear, the most common of which are rake face wear, flank face wear, and boundary wear. Rake face wear is primarily caused by the intense friction between the chips and the rake face, forming a crater near the cutting edge. As wear intensifies, the crater gradually expands, eventually leading to blade fracture. Flank face wear is caused by friction between the flank face and the workpiece surface, forming a wear band. This reduces the tool’s clearance angle, increases cutting forces, and affects machining accuracy. Boundary wear typically occurs at the junction of the primary and secondary cutting edges, where cutting conditions are most severe, with relatively high temperatures and pressures, making it prone to severe wear.
The main causes of tool wear include mechanical wear, thermochemical wear and adhesive wear.
Wear is caused by the scraping effect of hard particles in the chips and workpiece material on the turning tool surface, especially when machining high-hardness materials. Thermochemical wear occurs when the turning tool material reacts chemically with the surrounding medium at high temperatures, causing corrosion or oxidation of the tool surface material, thereby reducing the tool’s wear resistance. Adhesive wear refers to the adhesion between the chip and the front cutting edge, or the workpiece and the back cutting edge, under the action of high temperature and high pressure. When the chip or workpiece separates from the tool, it will carry away part of the tool surface material, causing wear. In addition, factors such as cutting parameters and the degree of matching between the tool material and the workpiece material also have a significant impact on the wear rate of the turning tool.
To extend the life of turning tools and reduce wear, properly selecting cutting parameters is crucial. Cutting speed, feed rate, and depth of cut are the main cutting parameters that affect turning tool wear. Generally speaking, excessively high cutting speeds can cause a sharp increase in cutting temperature, accelerating thermochemical and adhesive wear of turning tools; excessive feed rates can increase cutting forces and exacerbate mechanical wear; and excessive depths of cut can increase the load on the turning tool and easily lead to tool chipping. Therefore, in actual machining, the appropriate cutting speed, feed rate, and depth of cut should be selected based on the workpiece material, tool material, and machining requirements to reduce tool wear.
When a turning tool wears to a certain extent, it needs to be sharpened to restore its cutting performance. The purpose of turning tool sharpening is to give the tool a reasonable geometric angle and a sharp cutting edge to ensure processing quality and efficiency. When sharpening the turning tool, the appropriate grinding wheel should be selected according to the different tool materials and processing requirements. For example, high-speed steel turning tools are often sharpened with an alumina grinding wheel, while carbide turning tools are often sharpened with a silicon carbide grinding wheel. During the sharpening process, it is important to control the speed and feed rate of the grinding wheel to avoid cracking or annealing of the tool due to overheating. At the same time, it is necessary to ensure that the tool angle after sharpening meets the design requirements, and the main cutting edge, secondary cutting edge, and finish edge should be smooth and flat, without burrs or notches.
After sharpening, turning tools require necessary inspection and trimming to ensure their quality. This inspection includes the tool’s geometric angle, cutting edge sharpness, and surface roughness. Tools such as an angle ruler and a template can be used to measure the tool angle. The cutting edge should be visually inspected or magnified for sharpness and defects. If the tool angle does not meet the requirements or the cutting edge is defective, it should be re-sharpened or trimmed. Furthermore, before using a sharpened turning tool, it is best to perform a test cut to check the quality and dimensional accuracy of the machined surface. Based on the test cut results, the tool angle can be fine-tuned to achieve the best cutting effect. Only turning tools that have undergone rigorous inspection and trimming can perform well in the process, improving production efficiency and processing quality.
