522 



♦ KNO\VLEDGE • 



[JONE 19, 1885. 



WATCH-MAKING AT THE INVENTIONS 

 EXHIBITION. 



{Continued from p. 500.) 



IN the Escapement Department (Fig. G) are made 

 several of the pieces (thirteen in all) involved in the 

 escapement, including the roller and roller jewel, the pallet 

 and its two jewels, escape-wheel, ic. The garnec pallet 

 stones are placed thirty or forty together, on a steel block 

 ground, and finished on one side and then on the other. 

 The edges are finished the same way. They are then 

 stacked on a graduated plate, and marked with a diamond 

 to be broken otT to a length. They are then put in a 

 grooved pallet pet at the desired angle for the impulse force. 

 All are finished with diamond dust on ivory laps. The 

 polishing is done with an oscilUtory motion. 



The escape-wheel cutting, which may be examined at the 

 Exhibition, is done by an automatic machine, provided with 

 two steel and four sapphire cutters. Fifty wheels are 



In the balance-making room, Fig. 7, a large number of 

 operations are carried on. The balance compensation Is 

 effected with exquisite delicacy and rapidity, and the 

 operation is most interesting. A disc is punched out of a 

 steel plate, centred, drilled, and turned to a fine measure. 

 A cup of pure copper somewhat larger is struck, and a ring 

 of bronze made, which, when the steel disc is placed in the 

 cup, shall just fill the interspace. The whole is placed in 

 the furnace and the ring is fused on the disc without 

 solder, the disc put in the lathe, and turned down to the 

 outer diameter of the balance-wheel, faced on both sides, 

 and drojjs out at a tiny circular plate of steel, framed in 

 bronze. It then goes into a lathe, where the steel is cut 

 away, so as to leave a shallow cup with a delicate wall of 

 the compensating combination. This goes into a die, and 

 two crescents are punched out of the plate, leaving the 

 cross-bar on which the wheel swings. It then goes into a 

 machine which removes the burr left by the die, and then 

 into a lathe which rotates it, while a tool drills, and another 

 taps, by a gauge, sixteen holes round its circumference, and 



Fig. 0. 



cut together, and for that puri)Ose they are threaded on to 

 a spindle. 



The movements of the machine are exceedingly inge- 

 nious. The cutters make 8,500 revolutions per minute, 

 and notwithstanding this enormous speed, the bearings are 

 so well made and looked after as never to become heated. 



One of the cutters, revolving at this spe^d, approaches 

 the wheels, and, passing longitudinally over them, makes 

 a first cut. The spindle then automatically moves one 

 step round, the distance equalling that between two 

 teeth, and the cutter makes its way through the wheels 

 again; this operation being repeated for the whole of the 

 fifteen teeth, when the second cutter is automatically 

 thrown into gear, and enlarges each of the cuts made in 

 each of the wheels by the first cutter. S ) ou with the 

 third, fourth, fifth, and sixth cuttern ; and, when the last 

 cutter has made its last and finibhing cut, the machine 

 stops— automatically, of course. The wheels are unthreaded, 

 and a fresh batch takes their place. 



a girl inserts the regulating screws. After this, the hair" 

 spring is fitted. The average weight of a balance-wheel is 

 8 grains. 



The hair-spring is considei-ed of sufficient importance to 

 have a department to itself. The springs are rolled from 

 fine steel-wire 022 of a centimetre in diameter, and drawn 

 between four diamonds, two for the faces and two for the 

 edges. The ultimate dimensions of the steel are 027 of a 

 centimetre wide and -008 thick ; fourteen lengths of inches 

 are then cut off, coiled up, placed in boxes, and then 

 hardened and tempered, after which they are cleaned by 

 immersion in acid, and blued. It is said that a pound of 

 the fine steel-wire employed for hair-springs costs at the 

 outside twenty shillings, an. , i into 17,280 springs, the 

 lowest value of which is computed at £1,400. The gauging 

 of the springs (Fig. 8) is a pretty process, which may be 

 seen in operation at the Exhibition. The gauge consists of 

 a dial-plate 7 in. in diameter and divided round its circum- 

 ference into 2,000 divisions. Under this plate is another 



