BLOCK MACHINERY. 



609 



Block Ma- wise with the pulley and its axis. This collar receives 

 chmery. t (j e en( j s Q f tne two ; ron ro( j 3 #_ The opposite ends of 



these rods are, as aoove mentioned, connected by a si- 



milar collar with the pulley A of the saw a. By this 

 connection, both the centre bit, which is screwed into 

 the end of the central axis^J and the saw sliding upon 

 the fixed tube b, are brought forward to the wood at 

 the same time, both being in rapid motion by their 

 respective pulleys. The power to bring them for- 

 ward is communicated to the machine by a bent le- 

 ver H, having a handle /; at the end, and at the other 

 end a fork, which receives the two ears or pins pro- 

 jecting from a collar i, fitted on the central axis, so 

 that the rotatory motion is not interrupted ; but the 

 collar cannot slip endwise upon the spindle. At k 

 is a spring of sufficient strength to counterbalance the 

 weight of the handle, and draw both the saw and cen- 

 tre bit back. In this state, the workman takes a 

 piece of wood and places it against the end of the fix- 

 ed tube b, so as to be nearly concentric with the saw ; 

 then by turning the screw D, he advances the cup at 

 the end of that screw, so as tb hold the wood fast ; this 

 being done, he depresses the handle /;, and, as above de- 

 scribed, brings the centre bit and the saw both to- 

 gether against the wood. The former bores the cen- 

 tral hole, while the latter cuts out the circular peri- 

 phery of the intended sheave : then raising the han- 

 dle /i, the saw and borer retreat, and the round piece 

 of wood may be removed to make way for another 

 rough scantling. 



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. 

 Coating The conking engine. This ingenious piece of ma- 



engine, chinery is represented in Plate LXI. Fig. 1. It is 

 Plate used to cut the three semicircular holes which sur- 

 J.XI. round the hole bored by the crown saw, so as to pro- 



1 '2' '" 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 bolt 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 

 VOX.. III. PART IV. 



with the hook of a detent A, which, is pressed to- Block Ms- 

 wards the centre of the wheel by a spring. When chmeT y- 

 this detent is withdrawn by the linger, the circle A ""V~ 

 may be turned round till the next arm comes to the 

 detent, when ft 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 from' turning round. At the 

 lower end it is tapped, and has a nut r fitted upon it. 

 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 

 6pring 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 hookH, 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 h is withdrawn, and the wheel 

 turned round by one of its arms, till a succeeding arm 

 engages the tooth of the detent j then the lever is 

 drawn down towards the spectator, and cuts the se- 

 cond semicircle at 60 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 slieave 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 countennarked 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 

 4h2 



