Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helical toolpath by moving more or less linearly while the workpiece rotates. The tool's axes of movement may be literally a straight line, or they may be along some set of curves or angles, but they are essentially linear (in the nonmathematical sense). Usually the term "turning" is reserved for the generation of external surfaces by this cutting action, whereas this same essential cutting action when applied to internal surfaces (that is, holes, of one kind or another) is called "boring". Thus the phrase "turning and boring" categorizes the larger family of (essentially similar) processes. The cutting of faces on the workpiece (that is, surfaces perpendicular to its rotating axis), whether with a turning or boring tool, is called "facing", and may be lumped into either category as a subset.
Turning can be done manually, in a traditional form of lathe, which frequently requires continuous supervision by the operator, or by using an automated lathe which does not. Today the most common type of such automation is computer numerical control, better known as CNC. (CNC is also commonly used with many other types of machining besides turning.)
When turning, a piece of relatively rigid material (such as wood, metal, plastic, or stone) is rotated and a cutting tool is traversed along 1, 2, or 3 axes of motion to produce precise diameters and depths. Turning can be either on the outside of the cylinder or on the inside (also known as boring) to produce tubular components to various geometries. Although now quite rare, early lathes could even be used to produce complex geometric figures, even the platonic solids; although since the advent of CNC it has become unusual to use non-computerized toolpath control for this purpose.
The turning processes are typically carried out on a lathe, considered to be the oldest machine tools, and can be of four different types such as straight turning, taper turning, profiling or external grooving. Those types of turning processes can produce various shapes of materials such as straight, conical, curved, or grooved workpiece. In general, turning uses simple single-point cutting tools. Each group of workpiece materials has an optimum set of tools angles which have been developed through the years.
The bits of waste metal from turning operations are known as chips (North America), or swarf (Britain). In some areas they may be known as turnings.
Read more about Turning: Turning Operations, Lathes, Tooling
Famous quotes containing the word turning:
“I cannot say what poetry is; I know that our sufferings and our concentrated joy, our states of plunging far and dark and turning to come back to the world—so that the moment of intense turning seems still and universal—all are here, in a music like the music of our time, like the hero and like the anonymous forgotten; and there is an exchange here in which our lives are met, and created.”
—Muriel Rukeyser (1913–1980)
“Parenting can be established as a time-share job, but mothers are less good “switching off” their parent identity and turning to something else. Many women envy the father’s ability to set clear boundaries between home and work, between being an on-duty and an off-duty parent.... Women work very hard to maintain a closeness to their child. Father’s value intimacy with a child, but often do not know how to work to maintain it.”
—Terri Apter (20th century)
“Then turning to the disciples, Jesus said to them privately, “Blessed are the eyes that see what you see! For I tell you that many prophets and kings desired to see what you see, but did not see it, and to hear what you hear, but did not hear it.””
—Bible: New Testament, Luke 10:23,24.