426 



BOOKBINDING 



thereon, also similarly split. This pinion fits upon tho split pin. Above, there is 

 cross section of a hollow coupling cap, with steel tongue across, that fits into both tho 

 cuts of tho screw pin and pinion boss, so that, when lowered upon each other, they 

 must all turn together. In tho middle and on tho top of the upper piece, o, the large 

 wheel #, runs loose upon its centre, and works into tho two pinion wheels, 1 1 (fig, 168). 

 The wheel has a fly nut with wings mounted upon it. 



It will now be soon, when tho plough is in its place, as at fig. 1 65, that if it be pushed 

 to and fro by tho right hand, and tho nut occasionally turned by the left, tho knives, 

 or cutters, will bo protruded downwards at the same time, and these either will or will 

 not advance as the coupling caps, u u, are on or off. 



169 



When the edges of a number of copies of the same book have to be cut, the opera- 

 tion is greatly accelerated by the use of Wilson's, or other cutting machines (fig. 169), 

 which are adapted for working either by hand or by steam-power. 



The cutting machines consist of an iron sliding table fitted with an upright plate at 

 light angles to the surface of the table, against which the backs of the pile of books 

 about to have their fore-edges cut are placed. By means 'of a turning wheel the fore- 

 edges of the pile of books are then brought in tho exact position proper to receive tho 

 descending knife-edge. This knife, long enough to roach from side to side of the 

 table, and therefore along the whole range of books placed upon it, is fitted into a 

 frame so as to act on tho principle of tho guillotine, and cither by a directly downward or 



