The geometric angle of the turning tool and the selection principle

The turning tool is usually a turning tool positioning rotary tool, and the machining center tool is called a rotary tool;
In order to determine the sharpness of the cutting edge and its position in space, a coordinate system must be established, which is composed of three reference planes. Take the external turning tool as an example to introduce the geometric angle of the turning tool.
Base plane: The plane passing through the selected point of the main cutting edge. This plane contains the main cutting edge when the main cutting edge is horizontal and is parallel to the bottom surface of the turning tool installation, that is, the horizontal plane. This plane is mainly used as a reference plane for measuring the spatial position of the rake surface.
Cutting plane: The plane that passes through the selected point of the main cutting edge and is tangent to the main cutting edge and perpendicular to the base surface. This plane is mainly used as a reference plane for measuring the position of the main flank in space.
Main section: A plane passing through the selected point of the main cutting edge and perpendicular to the base plane and the main cutting plane at the same time.
(1) Rake angle γ0 The included angle between the rake surface and the base surface, measured in the main section. The size of the rake angle affects the sharpness and strength of the cutting edge. Increasing the rake angle can sharpen the cutting edge, reduce the cutting force and reduce the cutting temperature, but an excessively large rake angle will reduce the strength of the cutting edge and easily cause damage to the cutting edge. The value range is: -8° to +15°.
The general principle of selecting the rake angle is: the value of the rake angle is related to the cutting material of the tool, the material to be processed, and the working conditions. When the cutting part of the tool is brittle and low in strength, the rake angle should be small. When the strength and hardness of the workpiece material are low, a larger rake angle can be selected. In heavy cutting and working conditions with impact, the rake angle can only take a small value, sometimes even a negative value. Generally, under the condition of ensuring the strength of the cutting edge of the tool, try to choose a large rake angle. For example, the rake angle can be 5°-15° when machining steel materials with cemented carbide turning tools.
(2) Main relief angle α0 The included angle between the main relief surface and the cutting plane is measured in the main section. Its function is to reduce the friction between the flank face and the workpiece. It also affects the strength and sharpness of the cutting edge just like the rake angle. The selection principle is similar to the rake angle, which is generally 0 to 8°.
(3) Entering angle κ r The angle between the main cutting edge and the feed direction is measured in the base plane. Its function is embodied in affecting the working length of the cutting edge, the resistance to attack, the strength of the tool tip and the heat dissipation conditions. The smaller the entering angle, the greater the resistance to attack, the longer the working length of the cutting edge, and the better the heat dissipation conditions.
The selection principle is: when the workpiece is thick and rigid, a small value can be used; when turning a slender shaft, in order to reduce the radial cutting resistance to avoid bending of the workpiece, a larger value should be selected. It is usually between 15° and 90°.
(4), secondary deflection angle κ'r The included angle between the secondary cutting edge and the opposite direction of the feed, measured in the base plane. Its function is to affect the roughness of the processed surface, and reduce the secondary deflection angle to make the processed surface smooth. The selection principle is: during finishing, in order to improve the quality of the processed surface, a smaller value should be selected, generally 5 to 10°.
(5) The angle of inclination λs is the angle between the main cutting edge and the base surface, measured in the main cutting plane. The main function is to affect the direction of chip flow and the strength of the tool tip. Taking the bottom surface of the tool holder as the reference, when the main cutting edge is parallel to the bottom surface of the tool holder, λs =0, the chips flow out in the direction perpendicular to the main cutting edge. When the tool tip is the lowest point of the cutting edge, λs is negative, and the chips flow to the machined surface. When the tool tip is the highest point of the main cutting edge, λs is a positive value, and the chips flow to the surface to be machined.
Generally, the blade inclination angle λs is -5° to +10°. During finishing, in order to avoid scratches on the machined surface with chips, a positive value or zero should be used. When roughing or cutting harder materials, a negative value can be used to increase the strength of the cutter head.