Chapter XII.—EXAMPLES IN LATHE WORK.
Technical Terms used with Reference to Lathe Work.—Work held between the lathe centres is said to run true, when a fixed point set to touch its perimeter will have an equal degree of contact all around the circumference, and at any part of the length of the same when the work is cylindrical and is rotated. When such a fixed point has contact at one part more than at another of the work circumference, it is said to run “out of true,” “out of truth,” or not to run true.
Radial or side faces (as they are sometimes called) also run true when a fixed point has equal contact (at all parts of the revolution) with the work surface.
Work that is held in chucks is said to be set true when it is adjusted in the intended position.
To true up is to take off the work a cut of sufficient depth to cause a fixed point to touch the work surface equally at each point in the revolution.
To clean work up is to take off it a cut sufficiently deep to cause it to run true, and at the same time removes the rough surface or scale from the metal.
Roughing out work is taking off a cut which reduces it to nearly the finishing size, leaving sufficient metal to take a finishing cut, and reduce it to the proper size.
Facing a piece of work is taking a cut off its radial face.
When a radial face or surface is convex, it is said to be rounding or round, and when it is concave it is said to be hollow.