Positioning and clamping method of turning tool blade
The positioning of turning tool inserts is fundamental to ensuring cutting accuracy. Its purpose is to position the insert correctly on the tool shank, ensuring that the angle and positional accuracy of the cutting edge meet design requirements. Positioning accuracy directly affects the dimensional accuracy and surface quality of machined parts. Inaccurate positioning can cause changes in the cutting angle, increase cutting forces, exacerbate tool wear, and even lead to machining errors. The positioning of turning tool inserts primarily relies on contact between the insert and the locating surfaces on the tool shank. The locating surfaces typically include the bottom, side, and rear end faces. Bottom surface positioning ensures the blade’s accurate height position, side surface positioning limits the blade’s radial movement, and rear end face positioning controls the blade’s axial position. High precision is required for the locating surfaces, with flatness and perpendicularity generally controlled within 0.01-0.03mm to ensure stability and accuracy after the insert is installed.
There are many ways to position turning tool blades, and different positioning methods are suitable for different blade types and processing requirements. Common positioning methods include flat mounting, vertical mounting, and compound positioning. Flat mounting is to install the blade horizontally on the tool arbor, with the bottom and side surfaces of the blade in contact with the positioning surfaces of the tool arbor. This positioning method has a simple structure and reliable positioning. It is suitable for most common turning tool blades, such as diamond and square blades. Vertical mounting is to install the blade vertically. It is mainly used for cutting knives, grooving knives, etc. It can enhance the rigidity of the blade and withstand greater cutting forces. Compound positioning combines the characteristics of flat mounting and vertical mounting. Through the joint action of multiple positioning surfaces, it improves positioning accuracy and stability. It is suitable for high-precision processing or cutting of difficult-to-process materials. In addition, there is a hole positioning method, which uses the hole in the center of the blade to cooperate with the locating pin on the tool arbor to achieve positioning. This method has high positioning accuracy and is often used for positioning indexable inserts.
The clamping method for turning tool inserts is to securely fasten the positioned insert to the toolholder, preventing it from loosening or shifting during cutting and ensuring a stable cutting process. Common clamping methods include screw clamping, pressure plate clamping, wedge clamping, and elastic clamping. Screw clamping directly presses the insert against the toolholder with a screw. It features a simple structure and easy operation, making it suitable for small and medium-sized inserts, such as diamond-shaped and triangular inserts. The tightening force of the screw should be appropriate; excessive tightening may cause the insert to deform, while insufficient tightening may prevent clamping. Pressure plate clamping uses a pressure plate to press the insert against the toolholder. Adjusting the pressure of the pressure plate by adjusting the screw provides uniform clamping force, making it suitable for larger inserts. Wedge clamping uses the inclined surface of the wedge to clamp the insert, leveraging the force-amplifying effect of the inclined surface to provide strong and stable clamping force, making it suitable for high-speed cutting and high-volume machining. Elastic clamping relies on the spring force of an elastic element to clamp the insert. It features a compact structure and easy assembly and disassembly, making it suitable for small inserts and automated processing.
The positioning and clamping of turning tool inserts require adherence to certain principles and techniques to ensure reliability and precision. First, the positioning surfaces should be kept clean to prevent impurities such as oil and chips from affecting positioning accuracy. The positioning surfaces on the insert and toolholder should be cleaned before installation. Second, the model and specifications of the insert should match the toolholder to ensure full contact between the positioning surfaces and to avoid unstable positioning caused by point or line contact. During clamping, the clamping force should be evenly distributed to prevent deformation of the insert due to uneven force. For indexable inserts, ensure accurate indexing of the insert so that each cutting edge is in the correct cutting position. When adjusting the insert position, use a feeler gauge or dial indicator for precise measurement to ensure that the height and radial position of the insert meet the requirements. In addition, parts of the clamping device, such as screws, pressure plates, and wedges, should be inspected regularly to ensure they are intact and to avoid a decrease in clamping force due to wear of the parts.
Different machining scenarios require different positioning and clamping methods for turning tool inserts, necessitating the appropriate method to suit the specific situation. During roughing, where cutting forces are high, a strong clamping method, such as wedge clamping or pressure plate clamping, should be employed. Secure positioning should also be ensured to prevent the insert from loosening under heavy loads. During finishing, where high precision is required, a high-precision positioning method, such as hole locating combined with screw clamping, should be selected to ensure accurate positioning of the cutting edge and maintain surface roughness and dimensional accuracy. When machining difficult-to-machine materials such as stainless steel and high-temperature alloys, the high cutting temperatures can easily cause thermal deformation of the insert. Therefore, the clamping force should be appropriately increased, while ensuring good contact between the locating surfaces to prevent insert displacement due to thermal stress. In automated machining, to improve tool change efficiency, a fast-loading and unloading clamping method, such as elastic clamping or a quick-locking mechanism, should be employed to reduce auxiliary time. By choosing the right positioning and clamping method, the turning tool’s performance can be fully utilized, improving machining quality and efficiency.
