- published: 02 Jul 2015
- views: 2163919
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.)
[The women of Paris mourn their lost loved ones.]
Women
Did you see them
Going off to fight?
Children of the barricade
Who didn't last the night?
Did you see them
Lying where they died?
Someone used to cradle them
And kiss them when they cried.
Did you see them
Lying side by side?
Who will wake them?
No one ever will.
No one ever told them
That a summer day can kill.
They were schoolboys
Never held a gun
Fighting for a new world
That would rise up like the sun
Where's that new world
Now the fighting's done?
Nothing changes, nothing ever will
Every year another brat, another mouth to fill.
Same old story, what's the use of tears?
What's the use of praying if there's nobody who hears?
Turning, turning, turning, turning, turning
Through the years.
Turning, turning, turning through the years
Minutes into hours and the hours into years.
Nothing changes, nothing ever can
Round and round the roundabout and back where you began!