doubleturned

Doubleturned is an adjective used in manufacturing and mechanical design to describe a component or feature that has undergone two sequential turning operations, typically on a lathe. The term emphasizes a two-stage process rather than a single turning pass, and is often found in machining notes, catalogs, or shop-floor chatter rather than formal standards.

Origin and usage: The phrase is formed from double and turned, reflecting two passes of a cutting tool that produce two distinct diameters or shoulder features. While not codified in major standards, the term is widely understood among machinists to distinguish a part that has been prepared by successive turning steps from a single-diameter, or "single-turned," part.

Applications: In practice, doubleturned components include shafts, rods, or bushings that present two or more diameters along their length. For example, a doubleturned shaft may have a large-diameter section near one end, followed by a reduced-diameter shoulder created by a second turning pass. In design documentation, noting a part as doubleturned helps indicate the sequence of operations and potential tolerance considerations, such as parallelism between shoulders or concentricity of features produced in separate passes.

Limitations: The term is informal and may be interpreted differently by shops, so precise specifications should accompany it with dimensional charts, tolerances, and surface finish requirements.

See also: Turning, Lathe, Machining, Shoulder, Step.

References: No universal standard exists for the term; its meaning depends on context and company practice.