Lathe-turning is an art by which circular surfaces are formed by means of lathes; and lathes are machines for rotating objects in order that their surfaces may be made circular. Although lathes are principally used for making such surfaces, they are employed also for planing, screw-cutting, and a few other operations that will be mentioned.

In connexion with these processes for turning, modes of lining must be given in many cases, although a large number of objects can be commenced and completed by means of turning, without any lining being executed, as will be observed in the ensuing details.

Engineers' lathes are sufficiently described in a general manner at pages 133, 134, and 135; and it is now convenient to indicate the several uses of lathes for shaping various portions of machines in general. This will necessitate the introduction of additional apparatus and implements which are required for special work; such as grooving, screw-cutting, and other operations that are but very little known.

We now proceed to consider the paring of objects with regard to their lathe-turning, and also to other operations requisite in addition to turning, to produce the desired form for each object.