In Fig. 246 is shown a well known form of planing machine. Its work is to plane the surfaces of boards, and to cut the edges into tongues and groves, such as are required for flooring. This machine planes boards up to 24 inches wide and 6 inches thick, and will tongue and grove 14 inches wide.

[Ill.u.s.tration: FIG. 246.--24-INCH SINGLE SURFACER AND MATCHER.]

_Wood Turning._--To this ancient art Blanchard added, in 1819, his very ingenious and important improvement for turning irregular forms. A few efforts at irregular turning had been made before, but in the arts generally only circular forms had been turned. With Blanchard's improvement, patented January 20, 1820, any irregular form, such as a shoe-last, gun-stock, ax-handle, wheel-spokes, etc., could be smoothly and expeditiously turned and finished in any required shape. In the ordinary lathe the work is revolved rapidly, and the cutting tool is held stationary, or only slowly shifted in the hand. In the Blanchard lathe the work is hung in a swinging frame, and turned very slowly to bring its different sides to the cutting action, and the cutting tool is constructed as a rapidly revolving disk, against which the work is projected bodily by the oscillation of the swinging frame, to accommodate the irregularities of the form. In order to do this automatically, a pattern or model of the article to be turned was also hung in the swinging frame, and made to slowly revolve and bear against a pattern wheel, which, acting upon the swinging frame carrying the work, caused it to advance to or recede from the cutting disc exactly in proportion to the contour of the model, and thus cause the revolving cutters to cut the block as it turns synchronously with the model, to a shape exactly corresponding to said model.

[Ill.u.s.tration: FIG. 247.--BLANCHARD LATHE.]

In Fig. 247 is shown a perspective view of Blanchard's lathe, as patented January 20, 1820. H is a swinging frame, carrying the model T of a shoe last, and a roughed-out block U, partly converted into a shoe last. A sliding frame, fed horizontally by a screw, carries a pattern wheel K, that bears against the pattern T, and a rotary cutter E, acting against the roughed-out block U. The revolving disk-shaped cutter E is rotated by a pulley and belt from a drum, which latter is made long enough to accommodate the travel of the frame. The pattern T and block U are advanced to contact respectively, with pattern wheel K and cutter E by the swinging action of frame H, and as the pattern T and block U are slowly revolved, the travel of T against K is made to react on frame H and regulate the advance of U against E, with the result that the rough block U is cut to the identical shape of the pattern T.

Among modern developments in this art may be mentioned the patents to Kimball, No. 471,006, March 15, 1892, and No. 498,170, May 23, 1893, the latter showing ingenious means whereby shoe lasts of the same length, but varying widths, may be turned. A polygonal-form lathe is shown in patent to Merritt, No. 504,812, September 12, 1893; a multiple lathe in patents to Albee, No. 429,297, June 3, 1890, and Aram, No. 550,401, November 26, 1895; a tubular lathe in patent to Lenhart, No. 355,540, January 4, 1887; and a spiral cutting lathe in patent to Mackintosh, No.

396,283, January 15, 1889.

[Ill.u.s.tration: FIG. 248.--MORTISING MACHINE.]

_Mortising Machines_ have exercised an important influence in mill work in the joining of the stiles in doors, sashes and blinds, and in the making of furniture. The Fay & Egan machine is seen in Fig. 248. The self acting mortising machine was among the numerous early contributions of Gen. Bentham in woodworking machinery, and was described in his British patent No. 1,951, of 1793, a number of them having been made by him for the British Admiralty. Brunel's mortising machine for making ships' blocks is another early form described in British patent No.

2,478, of 1801. As representing novel departures in this art, the endless chain mortising machine shown in Douglas patent, No. 379,566, March 20, 1888, may be mentioned, and reissue patent, No. 10,655, October 27, 1885, to Oppenheimer, and No. 461,666, October 20, 1891, to Charlton, are examples of mortising augers.

_Special Woodworking Machines._--Of these there have been great numbers and variety. No sooner does an article become extensively used than a machine is made for turning it out automatically. Indeed, machines for cheaply turning out articles have, in many cases, led the way to popular use of the article by the extreme cheapness of its production.

Among various automatic machines for making special articles may be mentioned those for making clothes pins, scooping out wood trays, pointing skewers, dovetailing box blanks, cutting sash stile pockets, cutting and packing toothpicks, making matches, boxing matches, duplicating carvings, cutting bungs, cutting corks, making umbrella sticks, making brush blocks, boring chair legs, screw-driving machines, box nailing machines, making cigar boxes, nailing baskets, wiring box blanks, applying slats, gluing boxes, gluing slate frames, making veneers, bushing mortises, covering piano hammers, making staves and barrels, making fruit baskets, etc.

It is impossible to give in any brief review a proper conception of the immensity of the woodworking industry in the United States. It is estimated in the Patent Office that about 8,000 patents have been granted for woodworking machines. Besides this there are about 5,000 patents in the separate cla.s.s of wood sawing, about an equal number for woodworking tools, and these, with other patented inventions in wood turning, coopering, or the making of barrels, wheelwrighting, and other minor cla.s.ses, give some idea of the activity in this great field of industry.

The exports of wood and wooden manufactures from the United States in 1899 amounted to $41,489,526, of which $15,031,176 were for finished boards, $4,107,350 for barrels, staves and heads, and $3,571,375 for household furniture, but this is only an insignificant portion, for with a prosperous country, an abundance of wood, and a thrifty and ambitious nation of home builders, the home consumption has been incalculable.

CHAPTER XXIX.

METAL WORKING.

EARLY IRON FURNACE--OPERATIONS OF LORD DUDLEY, ABRAHAM DARBY AND HENRY CORT--NEILSON'S HOT BLAST--GREAT BLAST FURNACES OF MODERN TIMES--THE PUDDLING FURNACE--BESSEMER STEEL AND THE CONVERTER--OPEN HEARTH STEEL--SIEMENS' REGENERATIVE FURNACE--SIEMENS-MARTIN PROCESS --ARMOR PLATE--MAKING HORSE SHOES--SCREWS AND SPECIAL MACHINES-- ELECTRIC WELDING, ANNEALING AND TEMPERING--COATING WITH METAL--METAL FOUNDING--BARBED WIRE MACHINES--MAKING NAILS, PINS, ETC.--MAKING SHOT--ALLOYS--MAKING ALUMINUM, AND METALLURGY OF RARER METALS--THE CYANIDE PROCESS--ELECTRIC CONCENTRATOR.

Take away iron and steel from the resources of modern life, and the whole fabric of civilization disintegrates. The railroad, steam engine and steamship, the dynamo and electric motor, the telegraph and telephone, agricultural implements of all sorts, grinding mills, spinning machines and looms, battleships and firearms, stoves and furnaces, the printing press, and tools of all sorts--each and every one would be robbed of its essential basic material, without which it cannot exist. Steam and electricity may be the heart and soul of the world's life, but iron is its great body. King among metals, it gives its name to the present cycle, as the "Iron Age," and the Nineteenth Century has crowned it with such refinements of shape, and endowed it with such attributes of utility, and such grandeur of estate, that its powers in organized machinery have, for effective service, risen to all the functions and dignity of human capacity--except that of thought.

A crude gift of nature, in the mountain side, it remained, however, a sodden ma.s.s until extracted, refined, and wrought into shape by the genius of man. Yielding to the magical touch of invention, it has been cast in moulds into cannon, mills, plowshares, and ten thousand articles; it has been drawn into wire of any fineness and length to form cables for great suspension bridges; it has been rolled into rails that grill the continents; into sheets that cover our roofs; and into nails that hold our houses together. It has been wrought into a softness that lends its susceptible nature to the influence of magnetism, and has been hardened into steel to form the sword and cutting tool. From the delicate hair spring of a watch to the ma.s.sive armor plate of a battleship, it finds endless applications, and is nature's most enduring gift to man--abundant, cheap, and lasting.

Metallurgy is an ancient art, and the working of gold, silver and copper dates back to the beginning of history. Being found in a condition of comparative purity, and needing but little refinement, they were, for that reason, the first metals fashioned to meet the wants of man. Iron, somewhat more refractory, appeared later, but it also has an early history, and is mentioned in the Old Testament of the Bible (Genesis iv., 22), in which reference is made to Tubal Cain as an artificer in bra.s.s and iron. The iron bedstead of Og, King of Bashan, is another reference. That it was known to the Egyptians and the Greeks at least 1000 B. C., seems reasonably certain. The a.s.syrians were also acquainted with iron, as is clearly established by the explorations of Mr. Layard, whose contributions to the British Museum of iron articles from the ruins of Ninevah include saws, picks, hammers, and knives of iron, which are believed to be of a date not later than 880 B. C.

Iron ore is usually found in the form of an oxide (hemat.i.te), and its reduction to the metallic form consists in displacing the oxygen, which is effected by mixing carbon in some form with the ore, and subjecting the mixture to a high heat by means of a blast. The carbon unites with the oxygen and forms carbonic acid gas, which escapes, while the metallic iron fuses and runs out at the bottom of the furnace, and when collected in trough-shaped moulds, is known as pig iron.

[Ill.u.s.tration: FIG. 249.--PRIMITIVE IRON FURNACE OF HINDOSTAN.]

The first iron furnaces were known as _air bloomeries_, and had no forced draft. The first step of importance in iron making was the forced blast. An early form of blast furnace is shown in Fig. 249, which represents an iron furnace of the Kols, a tribe of iron smelters in Lower Bengal and Orissa. An inclined tray terminates at its lower end in a furnace inclosure. Charcoal in the furnace being well ignited, ore and charcoal resting on the tray are alternately raked into the furnace. The blowers are two boxes, connected to the furnace by bamboo pipes, and provided with skin covers, which are alternately depressed by the feet and raised by cords from the spring poles. Each skin cover has a hole in the middle, which is stopped by the heel of the workman as the weight of the person is thrown upon it, and is left open by the withdrawal of the foot as the cover is raised. The heels of the workman, alternately raised, form alternately acting valves, and the skin cover, when depressed, acts as a bellows. The fused metal sinks to a basin in the bottom of the furnace, and the slag or impurities run off above the level of the basin at the side of the furnace.

The great modern art of iron working dates from Lord Dudley's British patent, No. 18, of 1621, which related to "The mistery, arte, way and meanes of melting iron owre, and of makeing the same into cast workes or barrs with seacoales or pittcoales in furnaces with bellowes of as good condicon as hath bene heretofore made of charcoale."

The next step of importance after the blast furnace was the subst.i.tution of c.o.ke for coal for the reduction of the ore, which was introduced by Abraham Darby, about 1750.

Next came the conversion of cast iron into wrought iron. This was mainly the work of Mr. Henry Cort, of Gosport, England, who, in 1783-84, introduced the processes of puddling and rolling, which were two of the most important inventions connected with the production of iron since the employment of the blast furnace. Mr. Cort obtained British patents No. 1,351, of 1783, and No. 1,420, of 1784, for his invention. His first patent related to the hammering, welding, and rolling of the iron, while in his second patent he introduced what is known as the reverberatory furnace, having a concave bottom, into which the fluid metal is run from the smelting furnace, and which is converted from brittle cast iron, containing a certain per cent. of carbon, into wrought iron, which has the carbon eliminated, and is malleable and tough. This process is called _puddling_, and consists in exposing the molten metal to an oxidizing current of flame and air. The metal boils as the carbon is burned out, and as it becomes more plastic and stiff it is collected into what are called blooms, and these are hammered to get rid of the slag, and are reduced to marketable shape as wrought iron by the process described in his previous patent. Mr. Cort expended a fortune in developing the iron trade, and was one of the greatest pioneers in this art.

The first notable development of the Nineteenth Century was the introduction of the hot air blast in forges and furnaces where bellows or blowing apparatus was required. This was the invention of J. Beaumont Neilson, of Glasgow, and was covered by him in British patent No. 5,701 of 1828. This consisted in heating the air blast before admitting it to the furnace, and it so increased the reduction of refractory ores in the blast furnace as to permit three or four times the quant.i.ty of iron to be produced with an expenditure of little more than one-third of the fuel.

[Ill.u.s.tration: FIG. 250.--MODERN HOT BLAST FURNACE.]

An ill.u.s.tration of a modern blast furnace plant is given in Fig. 250. A is the furnace, in which the iron ore and fuel are arranged in alternate layers. The hot air blast comes in through pipes _t_ at the bottom, called tuyeres. As gas escapes through the opening _b_ at the top, it is first cleared of dust in the settler and washer B, and then pa.s.ses through the pipe C to the regenerators D D D, where it is made to heat the incoming air. The gas mixed with some air burns in the regenerators, and, after heating a ma.s.s of brick within the regenerators red hot, escapes by the underground pa.s.sageway to the chimney on the right. When the bricks are sufficiently hot in one of the regenerators, gas is turned off therefrom, and into another regenerator, and fresh air from pipe H is pa.s.sed through the bricks of the heated regenerator, and being heated pa.s.ses out pipe F at the top and thence to the pipe G and tuyeres _t_, to promote the chemical reactions in the blast furnace.

In the earlier blast furnaces a vast amount of heat was allowed to escape and was wasted. The utilization of this heat engaged the attention of Aubertot in France, 1810-14; Teague in England (British patent No. 6,211, of 1832); Budd (British patent No. 10,475, of 1845), and others. To enable the escaping hot gases to be employed for heating the hot blast regenerators a charging device is now used, as seen at a in Fig. 250, in which the admission of ore and fuel is regulated by a large conical valve, and the gases are compelled to pa.s.s out at _b_ and be utilized.

Among the world's largest blast furnaces may be mentioned the Austrian Alpine Montan Gesellschaft, which concern owns thirty-two furnaces. This is said to be the largest number owned by any one concern in the world, but most of them are of small size and run on charcoal iron. The furnaces of the United States are, however, of the largest yield, and the leading ones of these are:

No. Annual capacity Furnaces. in tons.

Carnegie Steel Co. 17 2,200,000 Federal Steel Co. 19 1,900,000 Tennessee Coal and Iron Co. 20 1,307,000 National Steel Co. 12 1,205,000

The present annual output of pig iron in the United States is about ten million tons, of which these four companies make about one-half.

[Ill.u.s.tration: FIG. 251.--PUDDLING FURNACE.]

When the iron runs from the bottom of the blast furnace it is allowed to flow into trough-like moulds in the sand of the floor, and forms pig iron. Pig iron can be remelted and cast into various articles in moulds, but it cannot be wrought with the hammer, nor rolled into rails or plates, nor welded on the anvil, because it is still a compound of iron and carbon with other impurities, and is crystalline in character. To bring it into wrought iron, which is malleable and ductile, it is puddled and refined, which involves chiefly the burning out of the carbon and silicon. The pig iron is remelted (see Fig. 251) in the tray-shaped hearth _b_ from the heat of the fire in the reverberatory furnace _a_, the reverberatory furnace being one in which the materials treated are exposed to the heat of the flame, but not to contact with the fuel. The hot flame mixed with air beating down upon the melted iron on hearth _b_ for two hours or so, burns out the silicon and carbon, the process being facilitated by stirring and working the ma.s.s with tools.

During the operation the oxygen of the air combines with the carbon and forms carbonic acid gas, which, in escaping from the metal, appears to make it boil. When the iron parts with its carbon it loses its fluidity and becomes plastic and coherent, and is formed into b.a.l.l.s called _blooms_. These blooms consist of particles of nearly pure iron cohering, but retaining still a quant.i.ty of slag or vitreous material, and other impurities, which slag, etc., is worked out while still, hot by a squeezing, kneading, and hammering process to form wrought iron that may be worked into any shape between rolls or under the hammer.

[Ill.u.s.tration: FIG. 252.--BESSEMER CONVERTER DURING THE "BLOW."]

_Bessemer Steel._--Steel is a compound of iron and carbon, standing between wrought iron and cast iron. Wrought iron has, when pure, practically no carbon in it, while cast iron has a considerable proportion in excess of steel. Steel making consists mainly in so treating cast iron as to get rid of a part of the carbon and other impurities. Of all methods of steel making, and in fact of all the steps of progress in the art of metal working, none has been so important and so far reaching in effect as the Bessemer process: It was invented by Henry Bessemer, of England, in 1855. About fifty British patents were taken by Mr. Bessemer relating to various improvements in the iron industry, but those representing the pioneer steps of the so-called Bessemer process are No. 2,321, of 1855; No. 2,768, of 1855, and No.

356, of 1856. The process is ill.u.s.trated in Figs. 252, 253 and 254. The converter in which the process is carried out is a great bottle-shaped vessel 15 feet high and 9 feet wide, consisting of an iron sh.e.l.l with a heavy lining of refractory material, capable of holding eight or more tons of melted iron, and with an open neck at the top turned to one side. It is mounted on trunnions, and is provided with gear wheels by which it may be turned on its trunnions, so that it may be maintained erect, as in Fig. 252, or be turned down to pour out the contents into the casting ladle, as in Figs. 253 and 254. At the bottom of the converter there is an air chamber supplied by a pipe leading from one of the trunnions, which is hollow, and a number of upwardly discharging air openings or nozzles send streams of air into the molten ma.s.s of red hot cast iron. The red hot cast iron contains more or less carbon and silicon, and the air uniting with the carbon and silicon burns it out, and in doing so furnishes the heat for the continuance of the operation.

When the pressure of air is turned into the ma.s.s of molten iron a tongue of flame increasing in brilliancy to an intense white, comes roaring out of the mouth of the converter, and a violent ebullition takes place within, and throws sparks and spatters of metal high in the air around, producing the impression and scenic effect of a volcano in eruption. In fifteen minutes the volume and brilliancy of the flame diminish, and this indicates the critical moment of conversion into tough steel, which must be adjusted to the greatest nicety. When the carbon is sufficiently burned out the blast is stopped and the converter turned down to receive a quant.i.ty of ferro-manganese or spiegeleisen (a compound of iron containing manganese), which unites with and removes the sulphur and oxide of iron, and then the lurid monster, with its breath of fire abated, and its energy exhausted, bows its head and vomits forth its charge of boiling steel, to be wrought or cast into ten thousand useful articles.

[Ill.u.s.tration: FIG. 253.--POURING THE MOLTEN METAL.]

[Ill.u.s.tration: FIG. 254.--SIDE VIEW, SHOWING TURNING GEARS.]

Like most all valuable inventions, Mr. Bessemer's claim to priority for the invention was contested. An American inventor, William Kelly, in an interference with Mr. Bessemer's United States patent, successfully established a claim to the broad idea of forcing air into the red hot cast iron, and United States patent No. 17,628, June 23, 1857, was granted to Mr. Kelly. The honor of inventing and introducing a successful process and apparatus for making steel by this method, however, fairly belongs to Mr. Bessemer, to whose work was to be added the valuable contribution of Robert F. Mushet (British patent No. 2,219, of 1856) of adding spiegeleisen, a triple compound of iron, carbon and manganese, to the charge in the converter. This step served to regulate the supply of carbon and eliminate the oxygen, and completed the process of making steel. The Holly converter, covered by United States patents No. 86,303, and No. 86,304, January 26, 1869, represented one of the most important American developments of the Bessemer converter.

The importance of Bessemer steel in its influence upon modern civilization is everywhere admitted. It has so cheapened steel that it now competes with iron in price. Practically all railroad rails, iron girders and beams for buildings, nails, etc., are made from it at a cost of between one and two cents per pound.

In recognition of the great benefits conferred upon humanity by this process, Queen Victoria conferred the degree of knighthood upon the inventor, and his fortune resulting from his invention is estimated to have grown for some time at the rate of $500,000 a year. In a historical sketch of the development of his process, delivered by Sir Henry Bessemer in December, 1896, before the American Society of Mechanical Engineers at New York, Mr. Bessemer was reported as saying that the annual production of Bessemer steel in Europe and America amounted to 10,000,000 tons. The production of Bessemer steel in the United States for 1897 was for ingots and castings 5,475,315 tons, and for railroad rails 1,644,520 tons. The extent to which steel has displaced iron is shown by the fact that in the same year iron rails to the extent of 2,872 tons only were made, as compared with more than a million and a half tons of Bessemer steel.

In the popular vote taken by the _Scientific American_, July 25, 1896, as to what invention introduced in the past fifty years had conferred the greatest benefit upon mankind, Bessemer steel was given the place of honor.

A recent improvement in the handling of iron from the blast furnace is shown in Fig. 255. Heretofore, the iron was run in open sand moulds on the floor and allowed to cool in bars called "pigs," which were united in a series to a main body of the flow, called a "sow." To break the "pigs" from the "sow," and handle the iron in transportation, was a very laborious and expensive work. The ill.u.s.tration shows two series of parallel trough moulds, each forming an endless belt, running on wheels.

The molten cast iron is poured direct into these moulds, and as they travel along they pa.s.s beneath a body of water, which cools and solidifies the iron into pigs, and then carries them up an incline and dumps them directly into the cars.

[Ill.u.s.tration: FIG. 255.--CASTING AND LOADING PIG IRON.]

_Open Hearth Steel_ is not so cheap as Bessemer steel, but it is of a finer and more uniform quality. Bessemer steel is made in a few minutes by the most energetic, rapid and critical of processes, while the open hearth steel requires several hours, and its development being thus prolonged it may be watched and regulated to a greater nicety of result.

For railroad rails and architectural construction Bessemer steel still finds a great field of usefulness, but for the finest quality of steel, such as is employed in making steam boilers, tools, armor plate for war vessels, etc., steel made by the open hearth process is preferred. It consists in the decarburization of cast iron by fusion with wrought iron, iron sponge, steel sc.r.a.p, or iron oxide, in the hearth of a reverberatory furnace heated with gases, the flame of which a.s.sists the reaction, and the subsequent recarburization or deoxidation of the bath by the addition, at the close of the process, of spiegeleisen or ferro-manganese. The period of fusion lasts from four to eight hours.

The advantages over the Bessemer process are, a less expensive plant and the greater duration of the operation, permitting, by means of sampling, more complete control of the quality of the product and greater uniformity of result.