What is the most likely cause of a taper measured from end to end after making a cut on a shaft mounted in a lathe?

The most likely cause of a taper measured from end to end after making a cut on a shaft mounted in a lathe is an offset tailstock. When the tailstock is not properly aligned with the spindle of the lathe, it can introduce a slight angle in the workpiece’s rotation. This misalignment causes the cutting tool to engage the workpiece at varying depths along its length, resulting in a taper rather than a straight cut.

In a lathe, the tailstock’s primary function is to support the end of longer shafts, maintaining the stability and alignment of the workpiece during machining. If this component is adjusted incorrectly or if the tailstock itself is worn or damaged, then the tool will not cut uniformly. The consequence is that the diameter of the shaft changes along its length, leading to tapering.

Understanding this helps enable troubleshooting practices in lathe operation where precise machining is necessary. Addressing tailstock alignment is a key maintenance point to ensure the accuracy of lathe work.