LATHE, in turning, is an engine used in turning wood, ivory, and other mate rials.
The lathe we are about to describe is made of iron, in the best manner. See Plate LATHE. Pig. 1, is art elevation of the whole machine frontwise; fig. 2, an elevation sideways ; fig. 3, an elevation of the lathe only on a larger scale ; in fig. 4, are two elevations of an apparatus to be attached to the lathe for drilling holes ; fig. 5, is an elevation of the rest ; and fig. 6, a face elevation of one of the puppets.
The frame of the lathe is of wood, and consists of two ground cells, a 6, two up rights, d d, morticed into them, and cross pieces, e .1; at top, connecting them toge ther; upon the uppermost of these pieces the bench sustaining the lathe is fixed; g is another bench, supported by iron brackets, to receive a vice or other tools, at the option of the workmen ; between the two uprights, d d, the axis of the great foot wheel turns; it is pointed at the ends and turns in small conical holes in pieces of hard steel let into the uprights, d d ; one of these holes is in the end of a screw, by turning which, the axis can be tightened up so as to turn very freely without any shake ; the axis is made of wrought iron, and the points at the end are of hard steel welded together ; it is bent in the middle to form a crank; and h is the connecting rod, by which it is moved from a treadle, I; the treadle is a piece of board, i, seen endways, in fig. 2, screwed to an axle, k, at one end, on which it turns, and at the other end is broader, to receive the workman's foot; in the middle a staple is fixed, and the connect ing rod, hooked to it; A is the great wheel of cast iron, and of considerable weight in the rim, wedged fast on the axis, and turns round with it; it is by the momentum of this wheel that it continues to turn, while the crank and treadle are rising, and consequently when the work. man exerts no power upon them. When the crank has passed the vertical posi tion, and begins to descend, he presses his foot upon the treadle, to give the wheel a sufficient impetus, to continue its motion until it arrives at the same position again, We now come to describe the upper part of the machine, or lathe, the wheel and treadle being only the first mover, it is shewn on a larger scale in fig. 3, and it is to this figure we shall refer in describ ing it; B B is a strong triangular iron bar, firmly supported by its ends, on two short pillars screwed at their lower ends to the bench; this bar is perfectly straight and the sides flat ; 121 E are two iron standards, called puppets, fitted upon the triangular bar, D, and fixed at any place by screws ; they are both alike, and one of them is shewn endways in fig. 6; it has an opening made in it at the bot tom, the inside of which is filed extreme ly true, to fit upon the upper angle of the bar B B, through each of the branch es, formed by the opening in the bottom mortices, are cut, as is well seen in fig. 3; these receive the end of a short piece of iron, 212, having a screw tapped into it ; it is by screwing this screw tight up against the underside of the bar, that the puppet is fastened upon it; a small piece of iron is put between the end of the screw and the underside of the bar to defend it from bruises by the latter ; the upper end of the puppets are per forated with cylindrical holes, to receive truly turned pins, it a, and which are fix ed at any place by screws, o o ; these holes must be exactly in a line with each other, when the puppets are set at any place upon the bar, and it is to accom plish this, that too much care cannot be taken in forming the bar perfectly straight and true in the first instance, and of sufficient strength to preserve its figure. F is another puppet, fixed on
the bar, in the same manner as D and E : it has a conical hole through its upper end, whose centre is exactly in the same line with the holes through the other two puppets D and E ; this conical hole is the socket for the mandrill, G, to turn in, be ing conical at that part, and fitting the socket with the greatest accuracy ; the other end is pointed, and turns in a hole made in the pin, a, of the puppet, D, and which, besides the screw, o, has another at its end tapped into a cock, screwed to the puppet, to keep it up to its work ; the mandrill has a pulley fixed on it, with three grooves of different sizes, to receive a band of catgut which goes over it, and round the great iron wheel, A A; it is by this that ,the'mandrill is turned. I is the rest, composed of three principal pieces, shown separate in fig. 5, one of these pieces, r, is filed to an angle with inside, and furnished with a screw similar to the puppets, whereby it can be fasten ed to the bar ; on each side of this, pieces of iron, s s, are laid on the bar, and are .fastened together by two short bars, t t, to which they are both screwed, the main piece, 2', b eing cut away to make room for them. L is the bottom part of the rest, supported on the two pieces, s s, it has a dove-tailed groove along the underside ; a button, with a head like a screw, is fastened to the top of the main piece, r, and is received into the groove ; when the screw of the piece, r, is turned, it draws the button down towards the bar, and as its head takes its hearing on the inside of the groove, it must hold the piece L fast down upon the pieces, a a ; when the screw is loosened, the whole rest can be moved along the bar B, the piece L can be slid backwards and for wards upon the pieces, s s, or it can be turned round upon the button of the piece, r, as a centre, at the convenience of the workmen ; and all these motions are firmly clamped by the screw be neath the bar. The piece L has at one end a short iron tube fixed to it, in this an iron pin is fitted, to hold at its upper end the cross bar, V, on which the tool is laid, a screw is fixed in the tube, and a nut upon it presses a piece of iron, 7r, upon the ends of two short pins going through the tube, the other ends take against the large iron pin of the rest, when the nut is unscrewed, the rest can be set higher or lower, or turned round obliquely, and fixed by turning the nut ; the bar, v, of the rest, is fixed on by a screw, so that it can he easily changed for another when worn, or fbr different work there should be two or three of dif ferent sizes with the lathe. The mandrill, G, of the lathe should be of iron, and at the part where it turns in the collar, F, it should have a piece of good steel welded round it, and turned very true in a lathe, and also the point at the end should be of steel ; a small hole is drilled down from the top of the puppet, F, into the collar, to supply it occasional ly with oil. The end of the mandrill, be yond the collar, is formed into a male screw, whereon to fix the work to be turned. The manner of holding the work varies in almost every instance, and is explained under the article ING ; in general, it is held in pieces of wood called cheeks, screwed to the man drill, they are turned hollow like a dish, and the work is driven into the cavity, as shown in fig. I.