Introduction to basic knowledge of metal processing tools

When choosing the angle of the tool, it is necessary to consider the influence of many factors, such as workpiece material, tool material, machining properties (rough and finishing), etc., which must be selected reasonably according to the specific situation. Generally speaking, the tool angle refers to the marking angle used for manufacturing and measurement. In actual work, due to the different installation positions of the tool and the change of the cutting motion direction, the actual working angle and the marked angle are different, but the difference is usually very small. .

Materials for making tools must have high high temperature hardness and wear resistance, necessary bending strength, impact toughness and chemical inertness, good manufacturability (cutting, forging, heat treatment, etc.), and not easy to deform.

Usually when the material hardness is high, the wear resistance is also high; when the bending strength is high, the impact toughness is also high. But the higher the material hardness, the lower its flexural strength and impact toughness. Due to its high bending strength, impact toughness, and good machinability, high-speed steel is still the most widely used tool material in modern times, followed by cemented carbide.

Polycrystalline cubic boron nitride is suitable for cutting high hardness hardened steel and hard cast iron, etc.; polycrystalline diamond is suitable for cutting non-ferrous metals, alloys, plastics and glass steel, etc.; carbon tool steel and alloy tool steel Now it is only used as tools such as files, dies and taps.

Cemented carbide indexable inserts are now coated with titanium carbide, titanium nitride, aluminum oxide hard layer or composite hard layer by chemical vapor deposition. The physical vapor deposition method under development can be used not only for cemented carbide tools, but also for high-speed steel tools, such as drills, hobs, taps and milling cutters. The hard coating acts as a barrier to hinder chemical diffusion and heat conduction, which slows down the wear rate of the tool during cutting, and the life of the coated blade is approximately 1 to 3 times longer than that of the uncoated blade. (Guide: Factors that cause deviations in the accuracy of sawing machines)

Due to the parts that work under high temperature, high pressure, high speed, and corrosive fluid medium, more and more difficult-to-machine materials are used, and the automation level of cutting processing and the requirements for machining accuracy are getting higher and higher. In order to adapt to this situation, the development direction of the tool will be the development and application of new tool materials; further develop the vapor deposition coating technology of the tool, deposit a higher hardness coating on the high toughness and high strength substrate, and better solve the problem. The contradiction between the hardness and strength of the tool material; further develop the structure of the indexable tool; improve the manufacturing accuracy of the tool, reduce the difference in product quality, and optimize the use of the tool.

According to the cutting motion mode and the corresponding blade shape, cutting tools can be divided into three categories. General tools, such as turning tools, planing tools, milling cutters (not including shaped turning tools, shaped planers and shaped milling cutters), boring cutters, drills, reamers, reamers and saws, etc.; shaping tools, the cutting edges of such tools It has the same or nearly the same shape as the cross-section of the workpiece to be processed, such as forming turning tools, forming planing cutters, forming milling cutters, broaches, conical reamers and various thread processing tools, etc.; generating tools are used to process gears by generating Tooth surface or similar workpieces, such as hobs, gear shapers, gear shaving cutters, bevel gear planers and bevel gear milling cutters, etc.

The structure of various tools is composed of a clamping part and a working part. The clamping part and working part of the cutter with integral structure are made on the cutter body; the working part (tooth or blade) of the cutter with insert structure is mounted on the cutter body.

The clamping part of the tool has two types: with hole and with shank. Hole cutters rely on the inner hole to be sleeved on the main shaft or mandrel of the machine tool, and transmit the torsion moment with the aid of axial keys or face keys, such as cylindrical milling cutters, sleeve face milling cutters, etc.

Tools with shank usually have three types: rectangular shank, cylindrical shank and tapered shank. Turning tools, planers, etc. are generally rectangular shanks; tapered shanks * taper to bear axial thrust and transmit torque by friction; cylindrical shanks are generally suitable for smaller twist drills, end mills and other tools. The friction force generated transmits the torsional moment. The shank of many shank tools is made of low-alloy steel, while the working part is made of high-speed steel butt-welded two parts.

The working part of the tool is the part that generates and handles chips, including the cutting edge, the structure to break or roll up the chips, the space for chip removal or storage, and the passage of cutting fluid. The working part of some tools is the cutting part, such as turning tools, planers, boring cutters and milling cutters, etc.; the working part of some tools includes cutting parts and calibration parts, such as drills, reamers, reamers, and internal surface drawing. Knife and tap etc. The function of the cutting part is to remove the chips with the cutting edge, and the function of the calibration part is to smooth the machined surface and guide the tool.

The structure of the working part of the tool has three types: integral type, welding type and mechanical clamping type. The overall structure is to make the cutting edge on the cutter body; the welding structure is to braze the blade to the steel cutter body; there are two mechanical clamping structures, one is to clamp the blade on the cutter body, the other is It clamps the brazed cutter head on the cutter body. Cemented carbide cutting tools are generally made of welded structure or mechanical clamping structure; porcelain cutting tools adopt mechanical clamping structure.

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