The coaks being inserted into the sheave, are ta ken to the drilling machine. Here a drill is in con stant motion. The workman applies a sheave against it, and quickly drills through both the coaks and also through that part of the wood of the leave which is between, them. The place where the hole is to be drilled is pointed out by a small dent in the casting of the coak, in the center of each semicircle. Into these holes the pins above mentioned are insert ed, and the sheave is taken to the rivetting hammer.
This is a small hammer mounted on an axis, so as to move up and down. The tail of the hammer pro jects beyond the axis, and is pressed down at inter vals by three cogs fixed into a small wheel, revolving by the machinery.' By pressing the tail, these raise the head of the hammer, and it falls partly by its own weight, and from being assisted by a strong spring which presses upwards beneath the tail, and throws the hammer down. This spring is fixed on a lever, the end of which rests upon an eccentric wheel, which can be turned round by a rope, connect ing it with a treadle placed beneath the machine. When the workman presses his foot upon this treadle, it turns the eccentric wheel, and raises up the lever, so as to strengthen the spring, and throw the hammer down with greater force. The workman holds the sheave upon the anvil, and the hammer strikes upon the pins and coaks so as to beat them down, and rivet them fast in their places. At first the hammer strikes lightly; but as the process goes on, the work man presses his foot on the treadle, which strengthens the spring, and makes the hammer strike more forci bly towards the end of the rivetting.
The conks being thus fixed fast in their places, are broached out to render the centre hole through them truly cylindrical. For this purpose, the sheave is placed upon a flat chuck at the upper end of a vet-. deal mandrel, which we suppose standing still, though it is capable of being turned round by the mill. A broach, or cutter, is brought down into the hole, to enlarge it to the true figure. The sheave is fixed truly concentric with the mandrel, by the end of the broach, which is cylindrical, and is not, there fore, the cutting part, being received into a hole in the end of the mandrel, which it exactly fits; This insures the broach and spindle being in one line; and as the cylinder part of the broach fills the hole through the coak, it fixes the sheave on the centre of the chuck. A clamp is now brought down upon the sheave, one end moving on a hinge fixed to the chuck, and the other forced down by a screw ; this clamp fixes the sheave on the chuck, and the machine is put in motion. The sheave with its mandrel are now turning round, and the broach is brought lower down into the end of the mandrel, so that the cutting part comes against the metal of the conk, and en larges the hole sufficiently to make it perfectly true and smooth. The cutting part of the broach is a steel cutter, or tooth, fixed into one side of the cy lindrical part of it. The inside of the hole through the coaks have spiral grooves made round in them in the casting, and these are too deep to be removed by the broaching. They are intended as receptacles for grease, which is a very necessary precaution, as blocks, when in use, cannot often be greased. The sheaves are now finished excepf the -turning of the groove in their edges. This is done in the Face turning lathe. (See Fig. 2. of Plate LXI.) The sheave A is fixed against a flat chuck at the end of a mandrel B, by an universal chuck, similar to that before described in the making engine, except that the centre pin, instead of having a nut, is tapped into the flat chuck and turned by a screw-driver. The sheave turns in such a direction, that the action of the work tends to screw it faster. By this means the slightest force is sufficient ; even turning the screw by the thumb nail will expand the chuck sufficiently to turn the sheave round, and the drift of the work will fix it perfectly fast. The mandrel B is turned round by an endless strap X, working on either of the drums D or E ; the former of these is fixed to -the mandrel, and the latter is fitted upon it to slip -round freely. Now when the strap is working on the loose pulley E, as in the figure, it slips upon the mandrel, and the machine stands still; but by moving the strap upon the other pulley, it turns the machine round. 'The tool a, for turning the sheave, is fixed in a slide rest, being held by a screw b. This at - taches,it to a dove-tailed slider d, which will move in a groove, on an assemblage of pieces marked F, in a direction perpendicular to the mandrel. The groove F of this slider is fitted to slide upon a parallel dove. tailed piece G, fixed down upon the frame of the machine. Both sliders are moved by screws. That which moves the lower slider F, is turned by a small a- winch handle at Y. When turned, it advances tin upper slider with its screw, the tool, and all the ap paratus towards e sheave, fixed at the end of th( mandrel. The screw of d has a pulley H placed or the end of it, but fitted to slip round, and e is an arm. fitted on the end of the screw, to slide to and from the pulley, but made with a fillet, so that it must always turn round with the screw. The central piece of the
arm e has a groove round it, which is embraced by an opening in the middle of a lever exactly the same as the lever in the mortising machine. One end of this lever is jointed to the solid piece F, and this is its fulcrum ; the opposite end, marked f, is jointed to a rod g, suspended in an iron loop h, fixed at its upper end to the holder for the tool a. By moving the rod g endwise, the arm e slides upon its spindle, and, when pushed towards the wheel H, intercepts a stub projecting from the wheel, which is always turn ing, and now carries the screw with it ; but when the arm is pulled away from the wheel, the connection is destroyed, and the pulley slips round on its spindle, which is the end of the screw. The wheel H is turn ed round by means of an endless band passing round a pulley k on the end of a spindle, carrying the wheel 1, which is turned by an endless screw up on the mandrel at I. The band passes over the pulley k, then Makes a turn round H, and goes to a pulley K, from which it returns to k. The pulley K is si tuated at the end of a spring M, fixed to a pillar of the frame. The elasticity of this spring is such as to cause a sufficient tension of the band to turn the wheel round, and the direction of the band allows the position of the pulley H to be altered, by turning the screw Y, without loosening or tightening it. N is a rest, similar to that used in a common lathe, fas tened by a screw passing down through the frame. The workman takes a sheave, and fixes it against the chuck at the end of the the mandrel B, fastening it tight by the screw in the centre ; then by pressing the strap X sidewise, it passes on the pulley D, and puts the mandrel in motion. The screw Y is now turned, till the tool at a advances so as just to cut the coak of the revolving sheave, (we suppose the screw of the slider d has been previously withdrawn, by turning back the handle 0, so as to bring the tool nearly into the centre of the sheave). The workman now pushes the rod g towards the, pulley H : this, as before described, puts the screw in motion; and moves the slider d, with the tool, away from the cell; ter of the sheave, turning it all the way across to a true flat surface. When the tool arrives at the out side of the sheave, the loop h, which moves at the same time, intercepts a nut n, screwed on the end of the rod g, and by this means draws the rod, relieving the arm e from the pulley H, so that the motion can not be continued to break or damage the screw or sliters. During the time the tool was traversing the face of the sheave, the attendant, having nothing else to do, was employed in turning the groove in the edge of a sheave, by a gouge placed on the rest N. The lathe is now stopped, by shifting the strap X upon the loose pulley E. The sheave is removed from its chuck, and turned with the other side towards it. Then the handle Y is turned back, to draw the tool a clear away from the sheave, and the handle 0 is turn ed back to bring the tool again to the center. The lathe is now set in motion, and the operation above de : scribed repeated, except that the groove on the edge does riot require to be turned a second time. In our , drawing, we have not been able to explain a mostinge nious contrivance in the pulley, which gives motion to the endless strap turning the lathe. It is found 1) experience, that a certain velocity is best for turning brass or other soft metals to the greatest advantage, or of cutting the greatest quantity without wearing the tool, but that wood will work best with a much great , er velocity. The sheave contains both the metal coak and the wood sheave ; and to.give it the proper ve locity for both, is the object of the contrivance in question. It is effected, by having two pulleys, or wheels, which give motion to the endless strap X. These are of equal size, placed close together, their axis being in a line. One revolves with the velocity proper for turning brass, and the other for wood. Now in the commencement of the ope ration, when the tool works upon the coak only the strap works upon the slowest of these two pullies ; but as the tool advances, and has got over the metal, and begins to cut the wood, the strap is shifted to the quick pulley, and turns the lathe.with an increased velocity. The tool a is merely an angu lar point ; but the slider d is so perfectly true and firm, that it cuts as even a surface as could be expec ted from a wider tool, and with this advantage, that the point will cut through every thing it meets with less danger of breaking than an edge. The tool is fitted into a holder, and held by the screw b, by loosening which it can be removed to make way for a sharp one. The lathe adapts itself readily for differ ent sized sheaves. The chuck may be unscrewed from the end of the mandrel, and another put on. The screw Y will allow of any thickness ; the nut n, on the end of the rod g, can be screwed along the rod, to adjust the diameter of the sheave ; and the rest N can be diawn out in the same manner as any common lathe.