What turning tools are required for machining different threads of precision parts
In the process of precision parts processing, when high-speed steel turning tools are used to turn threads at low speed, if turning tools with back rake angle Yp equal to zero degrees are used, it is difficult to remove the chips, and it is difficult to turn the thread tooth surface smooth.
Therefore, thread turning tools with a back rake angle of 5 °~15 ° can be used. However, when the turning tool has a back rake angle, the tooth profile angle is easy to change. At this time, the method of correcting the tool tip angle is used to compensate for the tooth profile angle error.
The thread turning tool with back and front angle can cut smoothly, reduce chip buildup, and turn threads with low surface roughness. However, because the cutting edge does not pass through the axis of the workpiece, the thread profile (axial profile) to be cut is not a straight line, but a curve. This error can be ignored for threads with low requirements generally, but it has a great impact on the tooth profile angle. Especially for thread turning tools with large back and front angles, the tip angle must be corrected. When turning triangular threads, when the thread turning tool with 10 °~15 ° back rake angle is grinded, the tool tip angle shall be reduced by 40,~1 ° 40,.
If the precision of the thread is required to be higher, the back and front angle should be smaller (0 °~5 °) to turn the correct tooth profile.
It must be pointed out that the thread turning tool with large back rake angle will not only produce thread profile deformation, but also produce a large back force Fp when turning precision parts. This force tends to pull the turning tool towards the inside of the workpiece. If the gap between the slide plate lead screw and the nut is large, the phenomenon of "knife cutting" (broaching) will occur.