This machine is easily adapted to cut sheaves of different dimensions, by unscrewing the saw from the centre piece of its pulley A, and putting on a larger or smaller one; and the same is the case with the cen tre bit, which is attached to the central axis, by screw ing into the end of it.
The conking engine. This ingenious piece of machinery is represented in Plate LXI. Fig. 1. It is used to cut the three semicircular holes which sur round the hole bored by the crown saw, so as to pro duce a cavity of the shape represented in the sheave S lying on the ground beneath the machine. To effect this, the sheave is fixed (by an universal chuck enter ing its centre hole) to a circle A, which has three arms extending from it. This circle has a short axis passing through a lever BC, of which C is the ful crum, formed by a pin projecting from the frame of the machine. D, E, F are three columns rising from the circular frame G. These sustain an upper frame, and two vertical rods a. Upon these, a frame slides, carrying a small mandrel b, which has the cutter fix ed at its lower end. The sliding frame has a screw at d, which prevents it descending too deep into the sheave ; and a catch at H retains it when raised up above a certain height, so as to hold it out of the way while the sheave is fitting in. The lever BC has a motion on its centre within certain limits, which are determined by two screws, one at e, and the other un seen, intercepting the end of a holt f, fitted to the underside of the lever ; but by withdrawing this bolt, the lever may be brought forward, so as to remove the sheave to some distance from the centre of the circu lar frame.
The circle A is confined from turning round on its •axis, by the end of one of its arms being engaged with the hook of h, which. is pressed to- B wards the centre of the wheel by a spring. When this detent is withdrawn by the finger, the circle A May be turned round till the next arm comes 'to the detent, when it is locked till again set at liberty by the finger. The universal chuck formerly mention ed, for fixing the sheave to the circle A, is an admi rable contrivance. The centre piece expands itself concentrically with the axis, in order to fill the centre hole of the sheave in the following manner. A pin is fitted through the centre of the axis of the wheel A, made cylindrical in the part where it fits the axis, but with a fillet to prevent it froniturning round. At the lower end it is tapped, and has a nut r fitted The upper end above the axis is formed conical, the smallest part being downwards. Round this is fitted a small ring of steel, the inside conical to fit the pin, and the outside cylindrical, the size of the inside of the cen tre hole of the sheave. This steel ring is divided into three segments, kept together by a piece of watch spring lapped round them, and contained in a groove turned round the outside of the ring, so that the springis lodged beneath the surface of the outside of the three segments of the ring. When the nut r is screwed down, and the pin pushed up, the spring surrounding the steel ring collapses the segments upon the smallest part of the cone, so that the chuck is of its smallest dimensions. One of the pieces of wood, rounded and centered in the crown saw, is now put with its central hole over the chuck. The nut r being screwed, draws the pin down, and the conical head of it expands the steel ring, so as to jamb fast in the cen tral hole, and fix the sheave upon the wheel A. This being done, the lever B is pushed as far as it will go towards the cutter ; and the spindle b, with its frame; being let down, by disengaging the hook H, its cut ter enters the centre hole, (we suppose it all the while revolving by its band,) and the lever B being drawn towards the spectator, it cuts a semicircle of its own diameter on one side of the centre hole, till the lever B is stopped by the point of the screw at e.
The lever is now pushed back to rest upon its oppo site screw, the detent Is is withdrawn, and the wheel turned round by one of its arms, till a succeeding arm engages the tooth of the detent ; then the lever is drawn down towards the spectator, and cuts the se cond semicircle at CO degrees distant from the for mer. This being done, the lever.is brought forward, the circle turned round, and the third hole cut. It must be noticed, that when the sheave is turned round with the circle A, the cutter still cuts a part of the wood, • and acts to enlarge the central hole to the proper fi gure, to contain the metal coak or centre. 'One side of the sheave being cut in this manner, the nut of the screw r is slackened, the sheave taken off, and turned the other side upwards, which is to undergo the same process. The semicircles on the different sides of the sheave are cut exactly opposite, by means of a small cylindric pin, with a head large enough to fill one of the semicircles. At the proper distance from the centre, this pin is countermarked in the circle A, and has a small spiral spring surrounding its tail, which throws it always upwards. While the first side of the sheave is cutting, this pin is pressed into the circle, level with its surface ; but when 'the second side is to be done, the sheave, while fixed to the circle, is turn ed about on its centre pin, till the pin jumps up into the first semicircle which comes over it, and locks the sheave from turning round farther. The screw r is now lightened to fix the sheave fast ; 'and in this position the sheave is ready for cutting, and the se micircles will be exactly opposite each other. The cutters unscrew from the end of the spindle, to change for different sizes, and this regulates the diameter of the semicircle. Its distance from the centre of the sheave can be increased or diminished by the screw opposite to e. The quantity which the centre hole will be enlarged, is determined by the screw at e; and the depth which the semicircle will be cut, is gauged by the screw d. And, lastly, the universal chuck can be changed for one larger or smaller, by removing the nut r, and putting in a fresh one. By these means, this engine will suit many different sizes of sheaves. The sheaves thus prepared, have the coaks fitted into them. These are cast in gun metal of the true-size, to fill the cavity cut by the soaking engine. Each sheave has two coaks, one shewn at L, below Fig. 1. Plate LXI. and the other at M. The former has a bar rel or tube re projecting from it, which passes through the central hole of the sheave ; but M is only a ring put in on the opposite side, and receives the end of the barrel, which is rivetted down in it, so as to hold both fast in their places. But besides this rivetting, three pins are put through both coaks and the sheaves, and rivetted fast. One of these pins passes through the centre ofeach semicircular projection of the soak. These pins are made of copper wire, from a coil of which they are cut by a small pair of shears held in the vice, and provided with a stop behind them, which regulates the length of the pins.