NEEDLE MANUFACTURE 



409 



liable to fly in pieces, they are partially encased by iron plates, having a proper slit 

 in them to admit of the application of the wires. The -workman seated in front of the 

 grindstone seizes 50 or 60 wires between the thumb and forefinger of his right hand, 

 and directs one end of the bundle to the stone. By means of a bit of stout leather 

 called a thumb-piece, of which A, fig. 1558, represents the profile, and B the plan, the 

 workman presses the wires, and turns them about with his forefinger, giving them 

 such a rotatory motion as to make their points conical. This operation, which is 

 called roughing down, is dry grinding ; because, if water were made use of, the points 

 of the needles would be rapidly rusted. It has been observed long ago that the 

 siliceous and steel dust thrown off by the stones is injurious to the eye's and lungs of 

 the grinders, and many methods have been proposed for preventing its bad effects. 

 The machine invented for this purpose by Mr. Prior is one of the most effective. 



A A, fig. 1559, is the fly-wheel of an ordinary lathe, round which the endless cord 

 B B passes, and embraces the pulley, c, mounted upon the axle of the grindstone, D. 

 The fly-wheel is supported by a strong frame, E E, and may be turned by a winch- 

 handle, as usual, or by mechanical power. In the needle factories, the pointing-shops 

 are in general very large, and contain several grindstones running on the same long 

 horizontal shaft, placed near the floor of the apartment, and driven by water or steam- 

 power. One of the extremities of the shaft of the wheel, A, has a kneed or bent winch, 

 F, which by means of an intermediate crank, o G, sets in action a double bellows, H i, 

 with a continuous blast, consisting of the air-feeder, H, below, and the air-regulator, i, 

 above. The first is composed of two flaps, one of them, a a, being fast and attached to 

 the floor, and the other, e e, moving with a hinge-joint ; both being joined by strong 

 leather nailed to their edges. This flap has a tail, g, of which the end is forked to 

 receive the end of the crank, G. Both flaps are perforated with openings furnished 

 with valves for the admission of the air, which is thence driven into a horizontal pipe, 



1559 





K, placed beneath the floor of the -workshop, and may be afterwards directed in an 

 uninterrupted blast upon the grindstone, by means of the tin tubes, N o o, which em- 

 brace it, and have longitudinal slits in them. A brass socket is supposed to be fixed 

 upon the ground ; it communicates with the pipe, x, by means of a small copper tube, 

 into which one of the extremities of the pipe, N, is fitted ; the other is supported by the 

 point of a screw, Q, and moves round it as a pivot, so as to allow the two upright 

 branches, o o, to be placed at the same distance from the grindstone. These branches 

 are soldered to the horizontal pipe, N, and connected at their top by the tube, P. 



The wind which escapes through the slits of these pipes blows upon the grindstone, 

 and carries off its dust into a conduit, E, fig. 1559, which maybe extended to s, beyond 

 the wall of the building, or bent at right angles, as at T, to receive the conduits of the 

 other grindstones of the factory. 



A^safety valve, j, placed in an orifice formed in the regulator flap, i, is kept shut by 

 a spiral spring of strong iron wire. It opens to allow the superfluous air to escape, 

 when by the rising of the bellows, the tail, i,, presses upon a small piece of wood, and 

 thereby prevents their being injured. 



The wires thus pointed at both ends are transferred to the first workshop, and cut in 

 two, to form two needles, so that all of one quality may be of equal length. For each 

 sort a small instrument,^. 1557, is employed, being a copper-plate nearly square. 



