In a parting-off operation, how is the cutting tool fed into the workpiece?

Explanation:

Parting-Off Operation

• Parting-off is a machining operation performed on a lathe where a thin cutting tool, known as a parting tool, is used to cut off a portion of the workpiece. This operation is commonly used to separate finished components from the raw material or to create grooves or recesses in the workpiece. The parting tool is fed perpendicular to the axis of the workpiece, slicing through it as the lathe spindle rotates.
• In a parting-off operation, the cutting tool is mounted on the tool post, and the tool post is attached to the cross-slide of the lathe. The cross-slide allows the tool to move in a direction perpendicular to the axis of the workpiece. During the operation, the operator manually rotates the cross-slide screw to feed the parting tool into the workpiece. This manual control ensures precision and allows the operator to adjust the feed rate based on the material type, tool geometry, and cutting conditions.

Why Option 2 is Correct:

1. Mechanism of Cross-Slide Feed: The cross-slide screw is a threaded component connected to the cross-slide of the lathe. When the operator rotates the screw, the cross-slide moves along its dovetail ways, carrying the tool closer to or away from the workpiece. This movement is precisely controlled, which is essential for delicate operations like parting-off.

2. Perpendicular Feed: Parting-off requires the tool to move perpendicular to the workpiece's axis to achieve a clean separation. The cross-slide screw facilitates this perpendicular feed, making it the most appropriate choice for the operation.

3. Manual Control: Unlike automated feeds, manual control allows the operator to feel the resistance encountered during cutting. This tactile feedback helps the operator avoid excessive tool pressure, which can lead to tool breakage or deformation of the workpiece.

4. Practical Application: In most lathe operations, especially in small workshops or for custom jobs, manual control of the cross-slide is preferred for parting-off. It provides the flexibility to accommodate variations in material properties and tool wear.