A patent was taken out in 1839 by Mr. Wilks, for making both the boxes and screws of tail vices and presses in malleable cast-iron. The peculiarities in the moulding processes are that the core for the hollow worm, or box, is made in a brass core box, divided longitudinally into three parts, which arc filled separately, and closed together with a stick of wood in the center, to stiffen the core and serve for the core print. The core box is then connected by rings, like the hoops of a cask: this completes the core, which is removed, dried, and inserted in a mould made from a model of the exterior of the box, constructed as usual.

In moulding the solid screw, the moulding-flask is a tube with a cap having an internal thread, exactly like that of the screw; the tube is filled with sand, and a plain wooden rod, nearly equal in diameter to the axis of the screw, is thrust in the sand, to form a cavity. The screwed tap is then attached to the flask, and a brass screw, exactly like that to be cast, is guided into the sand by means of the screw-cap, and taps a thread in the sand mould very accurately. The screw-cap is then removed, and the second part of the flask, in which the head of the vice-screw has been moulded, is fitted on, and the screw is poured.

After having been cast, the screws and boxes are rendered malleable in the usual way, except that they are placed vertically; in general the box is slightly corrected with a screw-tap.

Large quantities of screws have been produced by Mr. Warren's patent process for manufacturing screws of malleable cast-iron for joinery work: a most ingenious plan is employed therein for winding the models into and out of the solid sand-mould, which is thereby made beautifully smooth and accurate. After the last description the general method will be readily understood, if it be considered that the first side of an ordinary flask is rammed full of sand on an iron plate having conical projections like the heads of screws, in regular lines half an inch asunder, and ribs to form the channels by which the metal is to be admitted. The flask when filled is placed in a machine, beneath a plate of metal with screwed holes, also half an inch asunder, and each fitted with a pattern screw, terminating above in a crank like a winch handle, say of 1/4 inch radius.

• Applied by the Wrights' Vice- makers of Birmingham. See Technological Repository, vol. vi, p. 289. For the mode of soldering the thread in the box or the hollow screw of the vice, tee the same paper, and also vol i, p. 443, of this work.

680 Perkins's and scott's screws for cast-iron pipes.

Any of these screws on being turned by its crank with the fingers, would pierce the sand as in Wilks's process; but by employing a crank-plate pierced with a like number of holes, to receive the pins of all the cranks, the whole of the screw models are twisted in at once, and removed with the same facility.

The notches of the screws are cut by a circular saw; if large they may be moulded. The cast-iron screws are subsequently rendered malleable, by the decarbonizing process described in the former volume, pages 259-260.*

Mr. Perkins's patent cast-iron water-pipes, with screw joints, may be considered as another example. The patent pipes are connected with right and left hand screws and loose sockets, which draw the ends of the pipes into contact, or rather against a thick greased pasteboard washer interposed between them. The pipes are made entirely by foundry-work, and from patterns and:core-boxes divided in halves, in the ordinary manner. Mr. Perkins says that although the patent pipes possess several advantages over ordinary cast-iron pipes with the spiyot and faucet joint, they are produced at the same price, and save much ultimate expense in fixing.†

In Mr. Scott's subsequent patent for joining cast-iron and other pipes for various fluids, the method commonly known as the "union-joint" is employed, and which offers additional facility in the removal of one pipe from the midst of a series. Each pipe has at one end a projecting external screw, and at the other a projecting fillet or flange; the socket is cast loosely around the pipe, but is prevented from being removed or lost by the projections at each end of the same. The inside screw of the socket cast upon the first pipe a, screws upon the external screw of the next pipe b, until the socket comes in contact with the fillet on a, and thus draws a and b into close contact with the washer that is placed between them. One cast-iron pipe and its appropriate socket are moulded at one operation, which is curiously accomplished by the use of two sand cores, the inner of which is of the length of the pipe, and solid as usual; the outer core is made as a loose ring around the inner. The union-joint is differently produced by Mr. Scott in wrought-iron and soft metal pipes.*

• Date of Mr. Warren'8 patent for an improved machine for making screws, 4 th August, 1841; described in Rep. of Patent Inv. for March 1843, also in the Glasgow Mechanics' and Engineers' Mag., same date. The machine was constructed by Mr. Ingram of Birmingham, and is successfully worked by him.

† Date of patent, 21st Sept. 1841, described in Rep. of Patent Inv. Oct. 1841.

A peculiar method of making screw joints is employed in Mr. Rand's patent collapsible tubes for preserving paints, provi-sions, etc. The tin, whilst at the ordinary atmospheric temperature, is forced, almost as a cement, into the screwed recesses of brass or iron moulds; and the threads arc thus made to assume the helical form, with great rapidity, uniformity, and perfection.†

Indeed it is difficult, nay impossible, to find the limit of the methods employed in producing, or those of subsequently employing this interesting object, the screw; which not only enters in endless variety into appliances and structures in metal, wood, and other materials, but is likewise rendered available in most different yet important modes, as in the screw-piles for sandy foundations, screws for raising water, for blowing furnaces, ventilating apartments, and propelling ships.