BLOCK MA 



machine, e, e, e, are three screws, the same size as 

 the screw of the boring machine, and each furnished 

 with the same sized ring at its end. This enters the 

 impression made by the boring machine, so as to fix 

 the block in its proper position when the screw is 

 turned. This forces the other end of the block, 

 against a cross bar of the carriage, shewn separately 

 on the ground at Y. It has three steel circles, or 

 rings, J", fixed to it opposite the ends of the screw e. 

 Each of these rings includes two smaller rings, also 

 made with a sharp edge. Now the pressure of the 

 screw e forces the block, against these rings, so as to 

 print their impression in the wood ; and by this 

 means the block is held quite fast in the carriage 

 while undergoing the process of mortising. The 

 carriage has a large double wormed screw R attached 

 to it behind, and this is received through a nut, or 

 female screw, which is fitted to turn round in a fixed 

 collar, supported by a bar extended across the frame 

 of the machine. To this nut two wheels g, h, are 

 fixed ; the former is a large ratchet wheel, the latter 

 a cog wheel, which has a smaller one geering with it. 

 This is fixed on the end of a long axis k, on the extre- 

 mity of which M a winch r. When thisjs turned round 

 by the attendant, the nut of the screw is turned at 

 the same time, and the carriage moved slowly, either 

 back wank or forwards. This motion is only intend- 

 ed to adjust the carriage to the proper point of com- 

 mencement. The gradual advancement of the block 

 to each cut of the chisel, is produced by turning the 

 ratchet wheel g in this manner: The axis D has 

 an eccentric circle I fixed upon it ; which, as it re- 

 vulvvs, acts upon a roller K, fixed in one arm of a 

 bent lever, which cannot be wholly seen in the view: 

 the other end of this arm has a rod m jointed to it, 

 having a tooth in the middle, which engages the 

 teeth of the ratchet wheel, and turns it round a tooth 

 at a time, as the rod reciprocates backwards and for- 

 wards. The extreme end of this rod rests upon a le- 

 ver n, (except when it rises up by being drawn over 

 the sloping side of the tooth of the ratchet wheel,) 

 the centre of which is a pin fixed in the vertical 

 column of the frame. It is held up by a second lever 

 o, supported on a cock screwed on the frame. The 

 opposite end of this lever is made so thick and heavy, 

 that the weight of it is sufficient to raise up n and 

 m, so that the tooth of the latter will be too high to 

 intercept the teeth of the ratchet wheel in its motion. 

 The heavy end of the lever is kept up by a piece of 

 metal fastened to the side of the carriage at p. The 

 screws which fasten this, pass through oblong grooves 

 in it, so that it can be ii::ed at different parts along 

 the length of the carriage. By this means when the 

 carriage has advanced as far as intended, the loaded 

 end of the lever o falls off the piece p, and disengages 

 the rod m from the ratchet wheel. The fly-wheel 

 and drum which turns the machine, are, as before 

 mentioned, screwed together ; but they are fitted on 

 a cylindrical part of the axis, so as to turn freely 

 thereon, when it is not required to turn the axis D, 

 and work the machine. A conical wheel S, having 

 a hollow axis or tube centre piece, is fitted upon the 

 axis D, so as to slide freely endwise, but is confined 

 to revolve at the same time by fillets inserted into it. 

 TJie end of the tube of the wheel S is formed in- 



CHINERY. 613 



to a circular groove, which is embraced by a fork- Block Ma- 



ed lever L, centered in the opposite side of the cl " ncr ?- ^ 



frame. Now by moving the end of L towards the 



fly-wheel, the conical wheel S is thrust forwards, and 



jambed into the inside of the drum A. This exactly 



fits the wheel ; and the friction caused by the contact 



of the two conical surfaces, is sufficient to work the 



machine. On the other hand, when the lever L is 



pulled away from the fly-wheel, the conical wheel is 



drawn out from the rigger, and by that means the 



fly-wheel is detached from the axis, so as to revolve 



upon it freely without turning it ; but, to prevent 



any danger of the axis being turned by the friction 



of the fly-wheel upon it, the wheel S has another 



cone formed on the back of its rim, the bases of the 



two being conjoined. When the wheel is drawn back, 



this cone is jambed into a fixed ring M, supported by 



the frame of the machine, so as to be fixed fast, and 



prevent the axis from turning. 



The mortising machine is used in the following Method of 

 manner : The block brought from the boring ma- "sing the 

 chine has the print formed by the screw thereof mortising 

 i- i t .i j r r ,i ' TC machine, 



applied to the end or one ot the screws at ee. ir one 



double or threefold sheave block is to be mortised, 

 as shewn in the Figure, the centre screw alone is used 

 to hold it in ; but if two single sheaves are to be fixed 

 in, then only the outside screws are used, the centre 

 one being left loose. By screwing it tight, the block 

 is fixed between the double circle prints, before men- 

 tioned, on the bar Y ; and stops are situated on the 

 same bar. To guide the block to its proper position, 

 which is, that the hole bored for the commencement 

 of the sheave hole shall be vertical, suppose the block 

 fixed, the handle r is turned till the hole is brought be- 

 neath the sliding frame. The chisels are now adjusted. P'-ATt. 

 These are long square bars of steel TT, and are fas- :/ '* 

 tened to the frame by a clamp, seen separately at X. 

 This goes behind the cress bar of the frame, and has 

 two square holes through its ends, to receive the 

 chisel T, and two screws to bile it fast in tile square 

 holes ; at the same time that this keeps the chiseb from 

 slipping up and down, it fixes them fast to the frame 

 liE, by drawing the chisels forcibly against the 

 cross bars, by means of the clamps behind them. 

 The two screws of each clamp being blackened, the 

 chisels are put exactly over the holes which are to 

 become sheave holes, and screwed fast. The machine 

 is now put in motion by depressing the handle P. 

 This is at the end of a lever, the fulcrum of which is 

 a pin fixed in the column of the frame at t ; and a 

 short irm gives action to the end of the lever L, be- 

 fore described, so as to put the machine in motion. 

 At the first descent of the chisels, they cut down 

 through the whole depth of the holes previously 

 bored, so as to give them a flat side when they rise 

 up. The eccentric circle I, moving the bent lever and 

 rod in, turns the ratchet wheel round on both, and 

 advances the block a very minute quantity towards 

 the fly wheel; so that the chisels in descending cut 

 a fresh space, and in ascending the block advances. 

 In this manner it proceeds, with a most astonishing 

 rapidity, through the whole length of the intended 

 sheave hole. At this time, the loaded end of the 

 lever o drops off the piece p, previously adjusted, and . 

 raises the rod m, so that the farther advance of tie 



