610 



BLOCK MACHINERY. 



Block Ma- 

 chinery. 



Vlati 

 LXI. 

 Fig. I. 



Drilling 

 machine. 



Rivetting 

 liammer. 



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 coaking 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 to 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 tfrt 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 of each semicircular projection of the coak. 

 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. 



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 sheave 

 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 Block M.l- 

 the spring, and makes the hammer strike more forci- chinery. 

 bly towards the end of the rivetting. " 



The coaks being thus fixed fast in their places, Broaching 

 are broached out to render the centre hole through engine. 

 them truly cylindrical. For this purpose, the sheave 

 is placed upon a flat chuck at the upper end of a ver- 

 tical 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 sheas, 

 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 it. 

 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 hoi 

 through the coak, it fixes the sheave on the centre oi 

 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 coak, 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 except 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 ? ac< i '""*" 

 of a mandrel B, by an universal chuck, similar to that uf ATE 

 before described in the coaking engine, except that LXI. 

 the centre pin, instead of having a nut, is tapped into Fig. 2. 

 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 





