turning

Turning is a machining process in which a cutting tool removes material from a rotating workpiece to produce cylindrical or conical shapes. The operation is typically performed on a lathe and can be manual or computer numerically controlled (CNC). While closely associated with metalworking, turning is also common with plastics and wood, using specialized lathes for each material.

History and development: Turning dates to ancient times with bow and string lathes. The invention of precision lathes and screw-cutting in the 18th and 19th centuries enabled interchangeable parts and higher tolerances. CNC turning, which uses programmable controls, became widespread in the late 20th century, enabling automated production and complex geometries.

Process and equipment: A lathe holds and rotates the workpiece, typically in a chuck or collet, while a stationary cutting tool removes material. Key parameters are spindle speed (rpm), feed rate, and depth of cut. Cutting tools come in various forms for facing, turning, grooving, threading, and boring. Coolants or flood lubricants reduce heat, extend tool life, and improve surface finish.

Operations: External turning removes material from the piece’s outer diameter; internal turning (boring) enlarges or finishes holes. Combined operations include facing, threading, grooving, parting-off, and chamfering. In CNC turning, complex contours and features can be programmed with high repeatability.

Materials and applications: Turning is used on metals such as steel, aluminum, and brass, as well as on plastics and wood. Produced parts include shafts, pins, bushings, spacers, and components for automotive, aerospace, and general manufacturing.

Wood turning: A related discipline, wood turning employs a wood lathe and chisels or gouges to shape timber into bowls, spindles, vases, and decorative objects.

Safety and quality: Operators must guard against rotating parts and flying chips, use eye and hand protection, and follow correct setup procedures. Measurement tools and quality controls verify tolerances. See also lathe, woodturning, CNC turning.