

BLOCK MANUFACTURE 401 



spindle, which is turned by a pulley in the middle of it. The spindle is fitted in a 

 frame F F, moving in centres at e c, so as to rise and fall when moved by a handle f. 

 This brings the cutters down upon the blocks ; and the depth to which they can cut 

 is regulated by a curved shape g, fixed by screws upon the plate D, between the 

 blocks. Upon this rests a curved piece of metal h, fixed to the frame F, and inclosing, 

 but not touching, the pulley. To admit the cutters to traverse the whole length of 

 the blocks, the plate n (or rather a frame beneath it) is sustained between the points 

 of two centres. Screws are seen at I, on these centres. The frame inclines when the- 

 handle L is depressed. At ar is a lever with a weight at the end of it, counter- 

 balancing the weight of the blocks, and plate D, all which are above the centre on 

 which they move. The frame F is also provided with a counterpoise to balance the 

 cutters, &c. The cutters E E are circular wheels of brass, with round edges. Each 

 has two notches in its circumference, at opposite sides ; and in these notches chisels 

 are fixed by screws, to project beyond the rim of the wheel, in the manner of a plane- 

 iron before its face. 



This machine is used as follows : In order to fix the block, it is pressed between 

 the two pins (only one of which, at a, can be seen in this view), and the clamp d, 

 screwed up against it, so as just to hold the block, but no more. The clamp has two 

 claws, as is seen in the figure, each furnished with a ring entering the double prints 

 previously made in the end of the block. These rings are partly cut away, leaving 

 only such a segment of each as will just retain the block, and the metal between them 

 is taken out to admit the cutter to operate between them, or nearly so. In putting 

 the blocks into this machine, the workman applies the double prints to the ends of 

 the claws of the clamps, but takes care that the blocks are higher between the pins a 

 than they should be ; he then takes the handle /, and by it presses the cutters E E 

 (which we suppose are standing still) down upon the blocks, depressing them between 

 their pins at the same time, till the descent of the cutters is stopped by the piece h 

 resting on the shape g. He now turns the screws b b, to fix the blocks tight. The 

 cutters being put in motion cut the scores, which will be plainly seen by the mode of 

 adjustment just described, to be of no depth at the pin-hole ; but by depressing the 

 handle L, so as to incline the blocks, and keeping the cutters down upon their shape g, 

 by the handle /, they will cut any depth towards the ends of the blocks, which the 

 shape g admits. 



By this means one quarter of the score is formed ; the other is done by turning both 

 blocks together half round in this manner. The centres I are not fitted into the plate D 

 itself, but into a frame seen at B beneath the plate, which is connected with it by a 

 centre-pin, exactly midway between the two blocks A. B. A spring-catch, the end of 

 which is seen at r, confines them together ; when this catch is pressed back, the plate 

 D can be turned about upon its centre-pin, so as to change the blocks, end for end, and 

 bring the unscored quarters (i. e. over the clamps) beneath the cutters ; the workman 

 taking the handles f and i, one in each hand, and, pressing them down, cuts out tho 

 second quarter. This might have been effected by simply lifting up the handle L ; 

 but in that case the cutter would have struck against the grain of the wood so as to 

 cut rather roughly ; but by this ingenious device of reversing the blocks, it always 

 cuts clean and smooth, in the direction of the grain. The third and fourth quarters 

 of the score are cut by turning the other sides of the blocks upwards, and repeating 

 the above operation. The shape g can be removed, and another put in its place, for 

 different sizes and curves of blocks ; but the pins a and holding-clamps d will suit 

 many different sizes. 



By these machines the shells of the blocks are completely formed, and they are 

 next polished and finished by hand labour ; but as this is performed by tools and 

 methods which are well known, it is needless to enter into any explanation : the 

 finishing required being only a smoothing of tho surfaces. The machines cut so per- 

 fectly true as to require no wood to be removed in the finishing ; but as they cut 

 without regard to the irregularity of the grain, knots, &c., it happens that many parts 

 are not so smooth as might be wished, and for this purpose manual labour alone can 

 be employed. 



The lignum vitae for the sheaves of the blocks is cut across the grain of the wood 

 by two cross-cutting saws, a circular and straight saw, as before mentioned. These 

 machines do not essentially differ in their principle from tho great cross-cutting saws 

 we have described, except that tho wood revolves while cutting, so that a small saw 

 will reach the centre of a large tree, and at the same time cut it truly flat. These 

 machines cut off their plates from the end of a tree which are exactly the thickness for 

 the intended sheave. These pieces are of an irregular figure, and must be rounded 

 and centred in the crown saw, 



9. The crown saw is represented in fig. 143 (p. 402), where A is a pulley revolving 

 by means of an endless strap. It has the crown or trepan saw a fixed to it, by a 



VOL. L D D 



