Process Glossary — Start Here
Turning is a machining process where a single-point or indexable-insert cutting tool removes material from a workpiece that's rotating in a lathe. It's the inverse setup from milling: in turning the part spins and the tool stays largely stationary, fed along or into the rotating surface. Because the workpiece rotates around one axis, turning naturally produces round, axi-symmetric parts — shafts, pins, bushings — rather than the pockets and flat features milling is known for.
The workpiece is held in a chuck or between centers on a lathe and spun at a controlled speed. A single-point cutting tool — typically a carbide insert clamped in a steel holder — is fed into the rotating part, either along its length or radially toward its centerline, and shears material away as a continuous chip. Because one edge stays engaged in the cut the whole time — unlike milling, where each tooth only touches the material for part of a revolution — turning produces a continuous chip and, generally, a very consistent surface finish along the cut.
Facing cuts perpendicular to the spindle axis, squaring off the end of the workpiece and setting a reference face to measure from. Straight turning and taper turning move the tool parallel (or at an angle) to the axis, reducing diameter along the part's length — straight turning holds a constant diameter, taper turning changes it gradually from one end to the other. Boring is turning done on an internal surface: it enlarges and refines an existing hole rather than cutting an outside diameter. Threading, grooving, and parting off are more specialized turning operations, each with its own tooling, technique, and dedicated page on this site.
Every turning setup comes down to the same elements: the lathe, the workpiece, a way to hold that workpiece — a three-jaw or collet chuck for most work, or centers for long, slender parts that need support at both ends — and the cutting tool itself. The tool sits in a turret or tool post and moves on two axes, along the workpiece length and radially in and out, while the workpiece does all the rotating. That's the relationship worth remembering: on a lathe, the part spins and the tool doesn't.
This page covers the fundamentals. For specific operations and the numbers behind them, see the pages linked below.