Causes and Prevention of Scrapped Face Turning

05 August 2021

There are two common errors in end face machining. One is turning the end face into a concave surface, and the other is turning the end face into a convex surface. How do these two errors occur? How to prevent it? Let us analyze it together.


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The reason why the end face is uneven and concave

When turning the end face, although the 90° external turning tool can be used to turn the end face, in order to save time and trouble during the operation, the operator uses a 90° external turning tool to turn the end face . When the 90° external turning tool moves from the outer circle of the workpiece to the center of the workpiece, the turning tool is not normally turned with the main cutting edge, but with the secondary cutting edge. In this way, the back force generated during turning is the depth of cut The resistance force is perpendicular to the secondary cutting edge and points to the inside of the end face of the workpiece, so that the turning tool is always subjected to an external force during the turning process, which causes the turning tool to penetrate the end face of the workpiece deeper and deeper. After turning, the rear face forms a concave surface. The solution: try to turn the end face with a 45° turning tool. When using a 90 turning tool, turning from the outside to the inside is not possible, but turning from the center of the workpiece to the outside. In this way, when the tool is turning, the main turning edge participates in turning, and the cutting force generated is outward, which avoids the phenomenon of concave surface on the end surface.


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The reason why the end face is not flat into a convex surface

when turning the end face. Because the turning tool is not sharp, and during the turning process, the turning tool is moved outward due to the cutting resistance force, which drives the tool holder and the slide box to move outward. Especially when the turning tool is not compressed, it is more susceptible to force to move outwards. As a result, the turning becomes shallower and shallower, and the amount of turning is less and less, so that a convex surface is formed after the end face is turned. The solution: the turning tool is sharpened. During turning, the saddle must be fixed tightly to prevent the saddle from moving backwards and generating tool cuts. Press the turning tool tightly to prevent the turning tool from loosening during turning.

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