TURNING is the art of giving circular forms to articles of wood, ivory, metal, and other materials. Tho kinds of wood mostly used for common toys are alder, beech, birch, and willow; for the best Ton bridge ware, holly, chesnut, sycamore, apple, pear, and plum ; for hard general turnery—beech, box, elm, oak, and walnut ; and mahogany and pine for various purposes.
Nearly all kinds of turning are effected by the aid of the lathe. The principles of this valuable machine may be summed up in a few words. For every point marked by the workman, it produces a circle; and it may be described as a machine for moving the material to be wrought in such a manner that, being fixed opposite to the tool, any point in the circumference will act upon the whole circle in precisely the same way.
Pole-lathe.—This is the primitive and most simple kind of lathe. It consists of two upright pieces, each having a conical iron or steel point fixed on the side opposite the other, the two points being exactly in a lino ; one of these uprights, or puppet-heads, as they are called, is stationary ; the other can be moved along and fixed at any part of the bed by a wedge beneath. The wood t be turned being cut of proper length, the centre of one of its ends is pressed anainst the point of the fixed puppet; the point of the other is then brought against the centre of the other end, and the puppet wedged firmly in its place. Over the lathe, and at right angles to it, is a long flexible wooden pole or lath, whence the name lathe; one end, fixed firmly overhead; the other, just over the end of the work nearest to the left-hand puppet, has a cord or catgut attached to it, which passes once or twice round the work, and is fastened at the lower end to a treadle. The depression of the treadle and counteraction of the pole give an alternate rotatory motion to the work. Tho cutting tool is held upon the top of a fixed piece, between the two puppets and close to the work, called a rest, but can only be applied during the fall of the treadle; and thus a great loss of time is occasioned. On this account the pole-lathe is now but little used When commencing, a groove is cut to the extreme left of the work for the cord to work in ; and if it is required to use that part, the band is afterwards shifted to a finished part. The beginner has one great difficulty to overcome in turning soft wood. The tool requires to be held firmly almost on the top of the work, and the superfluous material shaved off; while the 'softness of the wood and the velocity with which it revolves cause the work to be easily spoilt by the least unsteadiness of hand. In other turning, the tool is held nearly opposite to the centre of the work, and the superfluous material is scraped away with little comparative danger of accident.
A modification of the primitive pole-lathe is used by watch-case makers, on account of the facility with which it can be arrested at any point of Its rotation. Some case-makers, the French in particular, make use of a large turning-toot instead of a lathe. It consists of an iron bar upon which slide three puppets, two to support the mandril with its back screw, and the other the rest; a long steel bow worked by the left hand serves instead of the polo and treadle. This turning tool work* easily, costs but little, and where many workmen are employed effects a great saving of room. Tools of this aort, from six inches to two feet long and upwards, are in use among jewellers, goldsmiths, watch and clockmakers, end many other artificers; and others without any mandril, in which the work is held between two points, as in the pole-lathe. One of this latter sort may be converted
into a very useful lathe for small work at a trifling expense, and still answer as a turning-tool if required.
The l'otter's.wheel is the simplest description of rotatory lathe; but it differs from other lathes' in being vertical instead of horizontal, c, fig. 1, is an iron crank, upon the lower part of which is placed a heavy foot-wheel, r; the lower end of the crank works upon a centre, r, fixed n the floor ; the upper in a collar, n, fastened to the work-bench, A, and supports the turnboard or chuck, D, upon which the clay to be worked is placed. Motion is given to the crank by means of a treadle placed at the back, and connected with the throw of the crank by a hook or rod. For large work the wheel is provided with a winch and bevil gear, and is turned by a boy. [EARTHENWARE.] Foot-lathe.—Fig. 2 is the front-view of a foot lathe, adapted to all ordinary work, whether in metals, ivory or wood. The headstock, H II, is of cast-iron, with a conical steel ring let into the front puppet within which the mandril works. A steel-pointed screw in the back of the headstock keeps the mandril steadily in its place. The beds are of cast iron, shown in the end view, fig 3, which also shows the manner in which the headstock is fitted upon and between tho beds, to which it is firmly fastened by two screws, A A, fig. 2. The crank, c, is of wrought-iron, supported at each end by a screw, n, fig. 2, 3, in the standard of the lathe. The fly or foot wheel. has four or five grooves on its edge, and gives motion to the mandril by means of a catgut band, which connects it with the smaller part of the mandril pulley, r. The object of having several grooves upon the wheel and pulley is to allow of the speed of the lathe being regulated according to the sort of work to be turned. But this arrangement only modifies what is called the quick motion. It is frequently necessary that the mandril should move more slowly than the crank; for which purpose a largo pulley is placed upon the mandril, and a small one upon the crank, and the two are connected by a band. The treadle is formed of a long iron bar suspended between two points at the hack of the frame, D, fig. 2 and 3, and cantos two shorter transverse bars at right angles, passing under the throws of the crank, and being connected with them by the hooks, E S: the front ends of these two pieces are screwed to the treading board, w. The standards of the lathe are prevented from altering their position by a rod passing close to the ground, and screwed to each standard at Q. The front-head, o, is of cast-iron fitted on to the beds nearly in the same manner as the headstock. The point of the cylinder, 5, to support one end of the work, must be exactly opposite to the centre of the mandril. There are several methods of arranging the cylinder and its screw; but the most convenient is as in the figure, with a screw J, and a winch-handle. K is a small screw with a binding piece beneath, which rests upon a flat filed on one side of the cylinder, and prevents the latter from shaking during turning. The rest, II, has a jointed lever binding-screw, and several tops to suit different pur poses, with a small screw to hold them steadily in the socket.