WHEEL-CHTTINO, a term applied to a particular branch of prac tical mechanics, which comprehends the modes of cutting the teeth in the wheels used by watch and clock makers and for other mechanical of cast-iron consisting of two parallel plates, the stouter the better, firmly connected together, but so that the plates are from 3 to 5 inches apart, to allow the dividing-plate PP to revolve between them. The plate PP is fixed firmly to the axis c (about S or 9 inches long), which works at its upper end in a collar d, in the upper plate, and its lower end in the centre of a screw, it : this axis c has a bole down from its upper end, about three-fourths of its length, to receive the smaller axes, arbors, or pinions of the wheels which are to be cut. a is a hori zontal slide, of which the vertical part E' is formed into a dove-tail, on which slides the vertical slide F, to which is securely attached a frame o, having two projecting sides through which pass two screws, one of which is seen at H. These screws have female centres to receive the ends of the arbor which carries the cutter r : j, a pulley on the cutter arbor which receives the band by which motion is communicated to the cutter r; 1, the handle of a lever, whose centre of motion is at r on a piece projecting from the back of the fixed dovetail to which is attached the connecting-rod for depressing tho slide a, and thereby passing the cutter through the wheel ; o, a piece attached to the back of the dovetail E', for the purpose of fixing the spring a, one end of which is attached to the slide and operates to bring up the slide after the cutter has passed through the wheel. The slide E is for the purpose of bringing the critter to the requisite distance from the centre of the wheel to be cut, and has a screw, not seen in the drawing, for the purpose of setting it fast when brought by the screw q to its proper place. The dividing-plate PP has on its surface a number of concentric circles, which occupy that portion of the plate nearest its circumference : these circles are each accurately divided into such a number of equal parts as are likely to be suitable for the wheels required to be cut ; the outer circles, being the largest, gene rally contain high numbers, such as 400, 360, 192, 168, 160, 150, 140, 136, 130, &c., and with these almost any common number of teeth can be cut. Firmly fixed on a moveable centre or joint attached to the frame of the engine is an index u, capable of a motion on its joint parallel to the plate rr, and having at its end a pin k, with a rather long conical point. On the plate Pr, at the intersection of each division with its
corresponding circle, is drilled a hole; and if thrlse holes are drilled quite through the plate all the better. The pin k is attached to the index u by a moveable piece which is acted upon by the screw s, and serves the purpose of shifting the plate PP any small quantity less than the distance of a single division en the plate; and 10 is a nut to set the pin k fast in any required position.
The index, being placed with its conical point k in one of the holes in any circle by means of slit v (say that of 360 divisions), is screwed fast by the screw t, and the elasticity of the index keeps it sufficiently tight in the hole to prevent the plate and arbor from moving round : if the end of the spring or index be now lifted up by the hand, and the plate be moved round till the next division or hole in the same circle comes under the conical point, and the point k be then dropped into It, the distance moved over by the plate, and also by the wheel which is screwed or otherwise fixed on to the end of the arbor c, w ill be ,Ltli part of a circle. The cutter having been adjusted to such a dis tance from the centre of the arbor c sa is required to cut a proper depth into the wheel, the operation of cutting is performed by bringing down the elide r which carries the cutter-arbor by the lover 1, the arbor being carried round by the band which passes round the pulley j, and a wheel similar to a lathe-wheel, which the operator keeps in motion by the foot acting on a treadle in the same way as In a common lathe. As soon as the critter hasthugh the tbicknem of the wheel, the pressure is taken off by which the cutting-frame or slide has been depressed, and it is brought back to the position it had before by the spring n, the plate is shifted one division, and the operation of cutting is repeated. It will be perceived that any number can be cut from each circle, provided the required number is an aliquot part of the divisions in the circle used : thus, on the circle of 360, by passing over two divisions between each cutting, 180 will be cut ; three divisions, 120 ; four divisions, DO; and so on.