Parting Off

In parting operations the workpiece rotates while the tool carries out a radial feed movement. As with face turning, the tool is fed from the periphery of the workpiece toward the center and the cutting speed is reduced to zero but here the similarities end.

As the cutting tool progresses toward the center, another factor takes effect. As the diameter of the workpiece is reduced, the radial cutting force will cause the material to break before the insert has cut through it. This results in a pip or burr being formed in the center of the workpiece. This pip will always be there after parting, but its size can be reduced by choosing the correct insert geometry, feedrate, and support for the sagging workpiece.

In a parting operation, there is material on both sides of the insert. This means that the tools used are narrow and that the length of the toolholder increases with an increased diameter. Therefore, stability becomes a critical factor. Since the size of the tool and toolholder must be optimized to meet requirements, only a small surface is present for drawing off heat, and therefore cutting fluid becomes important. Unfortunately, because of the space restrictions, the supply of cutting fluid is obstructed by the chips. Since chip evacuation is difficult and there is nothing against which to break the chips, the side surfaces can easily be damaged during the operation.

Credit:- https://www.americanmachinist.com/cutting-tools/cutting-tool-applications-chapter-6-grooving-and-threading