How to Correctly Choose Cutting Tools in Precision Mechanical Part Machining
In precision mechanical part machining, the selection of cutting tools is crucial as it directly affects machining accuracy, surface quality, and production efficiency. When choosing tools, multiple factors need to be considered comprehensively. The following are specific selection points:
Selection Based on Workpiece Material
Material Hardness: For materials with high hardness, such as quenched steel and titanium alloys, cutting tools made of materials with higher hardness and wear resistance, such as cemented carbides, ceramics, or cubic boron nitride (CBN), should be selected. For materials with lower hardness, like aluminum alloys and copper alloys, high-speed steel (HSS) tools can be used.
Material Toughness: Materials with good toughness tend to cause tool sticking during machining. Therefore, tools with sharp cutting edges and good chip evacuation performance should be chosen. For example, when machining stainless steel, coated carbide tools can be used. The coating reduces friction between the tool and the workpiece material, enhancing the tool's anti-sticking properties.
Selection Based on Machining Type
Turning: For external turning, external cylindrical tools are typically used. The tool geometry and cutting edge form can be selected based on the required machining accuracy and surface quality. For internal turning, internal hole tools are necessary, with their diameter and length determined by the size and depth of the workpiece's internal hole.
Milling: For surface milling, face milling cutters can be chosen, with their diameter selected based on the workpiece width and machining efficiency. End mills are commonly used for milling slots, steps, and contours, with different numbers of flutes and helix angles chosen according to specific machining requirements.
Drilling: For general drilling operations, HSS twist drills are suitable. For high-precision hole machining, carbide drills or gun drills can be selected.
Selection Based on Machining Accuracy Requirements
Dimensional Accuracy: When high machining accuracy is required, tools with higher precision grades should be selected. For example, in precision boring operations, micro-adjustable boring tools are necessary. These tools can precisely adjust the position of the cutting edge to ensure hole dimensional accuracy.
Surface Roughness: To achieve lower surface roughness, the cutting edge should be sharp, and the tool geometry should be optimized. For example, increasing the tool's rake angle can reduce cutting forces and surface roughness, while decreasing the tool's principal cutting edge angle can increase cutting thickness and improve surface quality.
Selection Based on Machine Tool Performance
Power and Torque: The power and torque of the machine tool determine the cutting force it can provide. When selecting tools, ensure that the tool's cutting parameters fall within the machine's power and torque range. If a machine with low power is used with a tool requiring high cutting forces, it may lead to machine overload, affecting machining quality and machine life.
Spindle Speed: Different tools are suitable for different spindle speed ranges. When selecting tools, determine the cutting speed based on the machine's spindle speed to fully utilize the tool's performance. For example, HSS tools have relatively low cutting speeds, while carbide tools can operate at higher speeds.
Selection Based on Production Efficiency
Tool Durability: Tool durability refers to the time a tool can cut between sharpenings. Choosing tools with high durability can reduce tool change frequency and improve production efficiency. For example, coated tools generally have higher durability than uncoated tools, maintaining good cutting performance for longer periods.
Cutting Parameters: Reasonably selecting cutting parameters such as cutting speed, feed rate, and depth of cut can enhance cutting efficiency. Within the limits of machining quality, try to use higher cutting parameters, but be cautious to avoid excessive tool wear or reduced machining quality due to overly aggressive parameters.
