Which cutting variable remains constant during turning as the workpiece diameter decreases in size?

Which cutting variable remains constant during turning as the workpiece diameter decreases in size?

• A. Spindle speed
• B. Feed rate
• C. Depth of cut
• D. Cutting speed

Answer: (A)

Spindle speed stays constant. The cutting speed at the tool is set by v = πDN, so as the workpiece diameter changes, the surface speed depends on both D and the RPM. If you keep the spindle RPM fixed while the diameter decreases, the cutting speed naturally drops. In many turning setups, the spindle speed is left at a fixed setting during a taper or when the diameter changes, while other parameters (like feed or depth of cut) are adjusted to maintain process goals. If the aim were to keep cutting speed truly constant, you would need to change the spindle speed as the diameter changes, not keep it fixed.

Spindle speed stays constant. The cutting speed at the tool is set by v = πDN, so as the workpiece diameter changes, the surface speed depends on both D and the RPM. If you keep the spindle RPM fixed while the diameter decreases, the cutting speed naturally drops. In many turning setups, the spindle speed is left at a fixed setting during a taper or when the diameter changes, while other parameters (like feed or depth of cut) are adjusted to maintain process goals. If the aim were to keep cutting speed truly constant, you would need to change the spindle speed as the diameter changes, not keep it fixed.