1902 Encyclopedia > Forge

Forge




FORGE, a fire urged by a blast for the purposes of the smith. Of late years many improvements have been made in its construction. Formerly the forge was almost made entirely of bricks, and many so constructed exist still. From the attention of engineers having been called to the special requirements and increasing wants of the day, the old forge has undergone many changes. Undoubtedly these changes are for the better. The modern forge leaves little to be desired. It is only in cases where the metal is of small dimensions, and the work of rare occurrence, that the old method of building them in brick is still resorted to. The forge seen in country smithies and in small shops is made entirely of bricks. It is generally built against a wall upon arches to a convenient height. The hearth, which should be made with fire-bricks, is sunk to a depth of three inches or more, according to the nature of the work for which it is constructed; so that the upper and outer course of brickwork forms a rim. About 2 feet 6 inches, more or less, above the hearth is placed the hood. This is also made of brick, and is built upon a flat iron rim. It is cone shape, and at the apex is an orifice leading into a flue for the escape of the smoke. In front of the forge is placed a water tank for quenching the work, tools, &c. The tuyere or tweer is placed at the back of the hearth, as well as a small water tank for keeping the nozzle from burning under the action of the severe heat to which it is submitted. A pair of bellows, either single or double, worked by a rocking staff or lever is placed on one side of the forge in a convenient position. The bellows are placed on each side, if the forge be provided with two fires; when this is the case it is called a double forge. Modern or the latest constructed forges are made almost entirely of cast or wrought iron. The wrought iron forges are as a rule portable for the purpose of ships, dockyards, &c. They are constructed with sheet iron of a suitable gauge, the pieces being riveted together, and generally have the bellows placed underneath the hearth so that it may be out of the way. This particularly applies to portable forges of any description. Cast iron forges (either single or double) are cast in one or two pieces, and are of superior thickness, so as to give strength and solidity. They are used as fixed hearths in shops. They are bricked up when the work is of a very heavy nature so as to support the weight. The hoods of these forges are also made of cast iron, and are bolted on to the main casting. They vary in shapes and sizes. Messrs Handyside of Derby have designed some which have found much favour in the English Government and other works. Some of the smaller forges are now fitted with a fan blast—to be worked by hand. These are very powerful, and give a very uniform current of air. They also have the advantage of being made entirely of metal, which adds considerably to their strength and lightness. The exertion in blowing is much less with them than with the ordinary bellows, from the motion being circular and the fan running between centres. At the Paris Exhibition (1878) there were several forges constructed upon an improved method. The blast was obtained by a pump, a reservoir being attached for maintaining the current—which was very easy to keep up.

In large smithies the hearths are all placed in a row or scattered about the shops in convenient situations, each having a flue passing through the roof. They are worked by a powerful air blast situated at one end of the building. The air is conveyed by a series of main pipes sunk to the depth of a few feet under the ground. Smaller tubes are employed to convey the blast to the hearths. Under these circumstances the smith has but to turn a small lever, in order to open or close the air-valve which is placed in a small standard at the side of each hearth. By this means the workman is saved much labour and consequently much time. Steam has also been adopted as a means of forcing air into the forge. With special apparatus for drying the steam it is very successful. It is, however, more adapted to large blast furnaces than those of the smithy. Another description of the forge is the battery forge. This is used in military service. It is constructed somewhat like a caisson. The bellows are situated in the place usually occupied by the ammunition chests. A box to contain coal, a set of tools, horse shoes, iron, and steel is attached to the body of the carriage, which is mounted on a pair of wheels.





The forge gives its name to " Forging," one of the most important arts connected with engineering work. The strength and durability of engines and other machinery in general depends to a very great extent upon the art and care bestowed upon those parts which have to sustain great weight, much strain, and an amount of wear and tear. Thus the smith holds in engineering shops a very important place. He has to depend upon his eye and judgment in many cases where the fitter and turner is assisted by drawings setting forth every detail. The smith, however, of the present day is not such an adept as his predecessor. The introduction of the steam hammer, stamps, &c, have to a great extent rendered his work nothing more than mechanical. To meet the urgent requirements of the present day, he has to study the engine and machine; that he has succeeded is evident, and the manufacturer can produce more work in less time than he could formerly. But though this is undoubtedly a gain, it has unfortunately been the means of rendering skilled manual labour in many branches of our industries almost superfluous. This being the case, the skill on which the older workmen so much prided themselves is slowly disappearing, and indeed has become almost extinct.

One great change in the history of forging was the introduction of the steam hammer in 1833 by Mr Nasmyth. By the means of that machine, the welding and forging of pieces of metal of any size have become comparatively easy. Mr Nasmyth's steam hammer has been improved upon by himself from that time, and is now to be seen in almost all engineering shops throughout the world. The tilt hammer is still in use, and for various purposes maybe said to be of great utility. But the smaller sizes of steam hammer are more convenient and manageable, and as a natural consequence are rapidly taking its place. To the steam hammer we are indebted for the Y anvil, which is used in the forging of rods and bar iron. Rolling mills are, however, much quicker, and are used in preference.

A forging machine, invented by Mr Ryder many years back, and still in full operation, possesses many qualities unattainable by any other known means. It consists of a series of small anvils of various sizes. These are held by set screws passing through the frame of the machine, which allow of the anvils being raised or lowered, so that a perfect adjustment might be obtained. The hammers are placed over the anvils, and work up and down in bearings, moved by an eccentric. This is worked by a cradle upon the head; the hammer is raised by a strong spiral spring. The strokes made by this machine vary from 600 to 1200 per minute. According to Mr Piatt (of Piatt Brothers, Oldham), one of the original makers of the machine, it is rather a squeeze than a blow which does the work. Many improvements have been added to it by Mr Piatt's firm; and the Bolton blacksmith, as it is commonly called, is now being extensively used in the Government workshops for the manufacture of bayonets, &c. The tools used are wedge-shaped, and the surface of the iron after forging, or rather squeezing, is said to be anything but hard or difficult to file up. The spindles of mules (cotton-spinning machines) are now forged by this tool, and indeed every description of small work. The contour produced by it is such that the work is almost as true as though it had been surfaced in the lathe. There have been several other machines upon Ryder's principle brought out, but none appear to answer so well as that designed by the original inventor.

Another invention, the steam stamp, is now most ex-tensively used. This is similar to a steam hammer; in place of the anvil and hammer head is placed a pair of dies, in which is cut the form of work necessary. The iron is placed over the die, the stroke is delivered, and the iron is forced into the shape of the die. Machinery and separate tools are now often forged in this hammer.

The quality of the coals used in forging is of the utmost importance; the coal preferred by smiths is that which makes plenty of coke, and which leaves after being burnt a quantity of white ashes.

The art of forging is by no means easy to acquire. Great practice is necessary to arrive at excellence in this important branch of our great industries.

See The Forge (published by the Society for Promoting Christian Knowledge), Vf. Harrison's Light of the Forge, and The Smith's and Metal Worker's Director. (D. A. A.)







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