FOOTNOTES

To teach an idle boy to read,His mind be sure to jog;But if he’s very bad indeed,You’ll be obliged to flog.Yet if you flog him day by day,He’llneverlearn to read;For boys require a lot of playTo make them work with speed.But young mechanics, if they errOr join the lazy team,Would all, as I suppose, preferTo be well flogged by steam.

To teach an idle boy to read,His mind be sure to jog;But if he’s very bad indeed,You’ll be obliged to flog.

To teach an idle boy to read,

His mind be sure to jog;

But if he’s very bad indeed,

You’ll be obliged to flog.

Yet if you flog him day by day,He’llneverlearn to read;For boys require a lot of playTo make them work with speed.

Yet if you flog him day by day,

He’llneverlearn to read;

For boys require a lot of play

To make them work with speed.

But young mechanics, if they errOr join the lazy team,Would all, as I suppose, preferTo be well flogged by steam.

But young mechanics, if they err

Or join the lazy team,

Would all, as I suppose, prefer

To be well flogged by steam.

If not, they had better not let me patent my flogging-machine. Luckily it is not invented yet.

Thecutting edgesof drills come under the same rules as other cutting edges. You might, for instance, hold a large drill flat on the rest, and use either edge as a turning-tool. You will see at once that these edges will not cut if made in the usual way, but only scrape. The bevel wants to be ground only to 3°, as before explained, to give the proper clearance, and the cutting edge requires to be then made by grinding back theuppersurface, which is just the same in effect as is produced by twisting the metalor cutting a spiral groove, which hollows out this upper surface and gives it cutting power. It is no use grinding a sharper-looking bevel, or making more of a point—you only weaken the edge;mornis quite pointed enough, though the first is a right angle and the second greater; and, for cast-iron, a rounded point, showing no angle at all, will do just as well, or better, when once it has begun to penetrate. Do not be deceived, therefore, by making drills look pointed and keen, for, I repeat, they are scraping tools only, unless you file an edge by bevelling back the upper face of each side of the point. If you were to make a very thick, strong drill, you might begin by grinding back the two sides to 3°, to form the accidental front line of the point or section angle, and then grind back,at 45° from this line, the upper face, by which you would do just what you did to give the graver cutting edges of 60°—only a drill thus formed must have a point of 90°. It would cut in two directions, like one for a drill stock and bow.

I hope my bigger boys will not pass over the remarks on cutting edges interspersed in this book, for, once understood, they will be found to be most valuable. Indeed, they cannot work intelligently until they understand exactly the nature and principles of the tools which they have to use. In drilling iron, use water or oil, or soap and water, or soda-water—either will do; but the holes are drilled in the ships’ armour-plating with soap and water to cool thedrill; and very well it answers, for these plates are several inches thick, but the holes are soon made. When working in brass and gun-metal, use no water, but work the drill quite dry. The same rules, in short, apply to drilling as to turning or planing metal; and if you could see the action of a well-made American twist-drill, you would recognise this similarity, for you would see the metal come forth in long, bright curls, as pretty and shining as those of your favourite young lady or loving sister—oneof which you have, I daresay.

To give you some idea of what a straight course a drill will take, if rightly made and skilfully used, I may tell you that a twist-drill has been run through a lucifer-match from end to end without splitting it; and as to thefinenesspossible, I have seen a human hair with an eye drilled through it, by which, needle-like, it was threaded with the other end of itself.

I told you how to bore a cylinder, which is but drilling on a larger scale, and in Fig. 65 I sketched the method of doing this in the lathe with a rosebit. But I did not explain another tool used just in the same way, but which will bore holes in solid iron wonderfully. Fig. 65, L, H, K, is one of these. This is an engineer’s boring-bit, and is made of all sizes, from that required to bore the stem of a tobacco-pipe—(don’t smoke, boys, it will dry up your brains)—to that which would bore a cannon. A rod of steel is forgedwith a boss or larger part at one end. This is centred in the lathe, and the centre-marks are well drilled, and not merely punched, especially that at the small end. The boss is then turned quite cylindrical, after which it is filed[4]away exactly to the diametrical line, as you will see by inspection of L. The end is then ground off a little slanting, to give, as before, about 3° of clearance. The cutting edge thus obtained, and the end in which the centre hole still remains, are carefully hardened. You thus have a tool which will bore splendidly, but you must give it entrance by turning a recess first of all in the work, or drilling, with a drill of equal size, a little way into the material. Used like the rosebit, this tool will run beautifully straight, so that you can bore very deep, long holes with it, and cylinders can be most beautifully bored with it. I think you would be able to make these tools with a little care; but, when you harden them, only heat and dip the extremities, or it is ten to one your steel rod will bend and warp in cooling, and you will not be able to rectify it. If the ends are quite hard, it is as well that the rest should be soft, as the tool will not then be so liable to get broken.

There are many other tools used for boring iron and steel, but you need not trouble yourself at present to learn anything of them—they are no use to you now.

I have headed this chapter “Hardening and Tempering”tools, but as yet I have only partially explained the process, which is a very curious one; and though theresultis highly necessary in many cases, it is by no means well understood what really takes place in the process, or why this effect should occur in steel, but not in iron, or brass, or other metals.

If you heat a piece of bright steel over a clear gas jet or fire which will not smoke it, you will see several colours arise as the metal gets hotter and hotter, until finally it becomes red. These are due to oxidation, which is so long a word that I am not sure I can stop to explain it thoroughly. Let us see, however, what we can make of it. The air we breathe contains two gases, oxygen and nitrogen, with a small proportion of a third called carbonic acid. Neither of thesealonewill support life, or keep the fire burning, or enable vegetables to live and grow, but it is the first which is in this the chief support. The second is only used by Nature as we use water to brandy, viz., to dilute it and render it less strong. If we breathed oxygen alone, we should live too fast, and wear out our bodies in a few hours. If we breathed nitrogen only, we should die, and so of carbonic acid. Now this oxygen seizes upon everything in a wonderful and sometimes provoking manner. If you leave a bright tool out of doors to get damp, down comes our friend oxygen and rusts it. It combines with the iron and makes oxide of iron, which is what we call rust. I suppose,however, this oxygen comes more from the water than the air, because water is made also of two gases, hydrogen and this same oxygen. It is certain that oxygen in this case always finds any bright tools that we leave about in the wet, and coats them with a red jacket very speedily. Then if you look at a blacksmith at work, you will see scales fall from the hot iron as he hammers it. These are black, but our old friend has been at work, and united with the red-hot metal and formed another oxide of iron, called black oxide. We can understand this. If a man eats a good deal, or drinks a good deal, he gets red in the face; if he eats till he chokes himself, he gets black in the face, and I suppose it is much the same when oxygen eats too much iron. Well, when we begin to heat the steel, down comes oxygen and begins his work; and first he looks very pale; then he gets more bilious and yellower; then he gets hotter and shows a tinge of red with the yellow forming orange; then he begins to get purple, then blue, then deeper blue; and finally black before he gets absolutely red and white hot.

Now to temper steel, we first heat it red-hot, not minding these colours, and then we cool it suddenly in cold water. This renders it very hard indeed. No file will cut it, or drill penetrate it; but if we strike it, behold it breaks like glass! This is too hard for general work, for the edge will break and chip if it meets with any hard spot in the metal, or chances to bite in too deep. Its teeth are too brittle, andso get broken off. For this reason we have to “let down,” or temper, the tool, and we proceed as follows: The part to be tempered is ground quite bright. It is then laid upon a bar of iron heated red-hot, or if small, it is held over a gas jet or in a candle; heated, in short, in any way most suitable and convenient. And now, first, our friend oxygen puts on a pale yellow face as before. This will do for turning steel and iron, but is still too hard for general work. Then comes the orange, and this presently tends slightly to blue; at which point, if the tool is instantly cooled in water, it will be found to bear a good edge, hard, but sufficiently tough for work. Most tools for metal and drills are let down to something between the yellow and blue, and we know that the more they approach blue, the softer they will be. Thus we can easily manage our tools;—some to bear hard blows, like axes, which are tempered to a blue colour; some like files, which a blow will break, but which are famous for their own special work—these are let down only to a pale yellow; others, like springs and saws, are let down to a more thorough blue, because they are required to be elastic and tough, but are not needed to be so particularly hard. Then tools like turnscrews, and bradawls, and gimblets are left even softer, sometimes not tempered or hardened at all, but just forged and ground to the required shape.

Now, I fancy some of my sharp boys will say that thefirst description I gave of the mode of hardening and tempering was not exactly like this; nor was it, yet in principle it is the same. For instance, if you give a drill to a smith to make, he will do as I then said. He will heat the extreme point red-hot, then dip the point in water, give a rub on the stone or bricks of the forge, and watch the colours. This can be done when the tool is of sufficient substance to retain heat enough after the edge has been dipped tore-heatthat edge sufficiently. In this case there is no need to chill the whole tool and then heat it again. But in the case of small drills and tools, pen-knife-blades, and other articles of this nature, there will not be sufficient heat retained, after dipping, to bring up to the surface the desired colours; for oxygen likes ahotdinner as well as you do, and if the iron is not hot enough he will have nothing to do with it.

One great difficulty you would find if you had much tempering to do, viz., that the articles bend under the operation, some more than others. Try this: Take a thin knitting-needle when the owner is not looking, and run off with it;—it is all in the cause of science! Heat it red-hot, and with a pair of pliers take it up and drop itsidewisein a basin of water. It will bend like a bow. Heat again, straighten it, re-heat, and this time pop it in lengthwise—endwise, point first—I mean (don’t you see that a round needle hasno sides, and puts me into a perfect quagmireof difficulty). However, you will understand this, and will find the needle not bent nearly so much as before, but still it is not straight. As I explain most things as I go on, I may as well explain why this bending occurs before I tell you how to straighten your work again. All metals expand with heat, and contract with cold. I am sureIcontract terribly in the winter until I have had plenty of hot soup, and hot roast-beef, and plum-pudding; and I know mytemperimproves, too, when I get expanded and warm. Well now, when you dropped your sister’s knitting-needle all hot on its side into the water, that side contracted before the other, and consequently the needle bent; but when you put it in the water,end on, it was cooled all round at once, and if you could but cool a piece of metal equally all over, inside and out,at once, all parts would shrink equally fast, and the article would remain straight.

But there is, unfortunately, another cause of this bending, which is, that all articles are not of such form that the same quantity of metal is on all sides of the axial line. Take a half-round file, for instance; one side is flat, the other curved, so that taking these two surfaces into consideration, one contains a great deal more metal than the other, and will not cool at the same rate. These articles are far more liable to bend than those whose sides are parallel. Another result of the hot mass being cooled most quickly on the outside is, that cracks are produced inthe latter, because, so to speak, the skin is contracted, and can no longer contain all the expanded metal within it. Hence, to make a mandrel for a lathe, it is common to bore it out first, before hardening, to remove this mass of metal, and to allow the water to touch it inside as well as out. Such mandrels seldom crack or bend.

The only way to straighten articles which have warped by hardening, is by what is called hacking or hack-hammering, which is nothing more than hammering the concave or hollow side with the edge of the steel pane of a hammer. This spreads the metal upon the hammered side, and, by expanding it, straightens the tool, for the hollow side, remember, is that which was too much shrunk or contracted. This is not an operation you will have to do, especially if you only harden the extreme points of the drills and little tools you make.

There is another way of hardening, not steel, but iron, called “case hardening,” because it puts a case of steel over the surface of the metal. Obtain a salt called prussiate of potash. It is yellow, like barley-sugar, but is poison. Heat the iron red-hot, and well rub it upon this salt, and then cool it in water. You will find that now a file will not touch it, its surface being as hard as glass. It is carbonised on its exterior, and made into hard steel. This can be done in another way, as gun-locks, snuffers, and many other things are case hardened. They are enclosedin an iron box, with cuttings of leather and bone-dust, and the box is luted about with clay and put in the fire. All the pieces get red-hot, and the leather chars and blackens, and some of it combines as before with the hot iron, and makes it into steel. And our friend oxygen is considerably at a loss in this case to find his way in, or he would make black scales again and spoil the work; or combine with the carbon (or charcoal) and make it into gas. Probably, however, as we shut up a little oxygen with the contents of the box, this changeDOEStake place, butjust as the gas rises the iron seizes it, and holds it fast.

And now, boys, I find it necessary to lay down the pen, which I see has almost run away with me, and written a good many more pages than I at first intended. Since I began to write I have visited the workshops at King’s College, and seen a sight to gladden my eyes. Boys carpentering, boys turning, boys filing; engines of real use, with single and double cylinders, finished, and in course of construction, and all these the work of schoolboys, whose hands and brains are alike engaged in this delightful branch of industry. Let no one, therefore, pretend that boys are not capable of executing good work of this kind in a masterly manner, or that what they do is always child’s-play, or I shall take up the cudgels in their behalf. I have also seen, in the Working-Men’s Exhibition, a very neat little engine, made by a boy only twelve years of age,which makes me hope and believe that the few hints upon wood and metal work which I have here thrown together will neither be unacceptable nor useless to those whom I address in these pages. In this hope I take my leave, and sign myself, with gratification and pride—

The boy mechanic’s faithful friend,

THE AUTHOR.

FOOTNOTES[1]In the drawing, they are all accidentally drawn of the same pitch.[2]The parts so jointed are highly exaggerated; when hammered down, the joint only forms a light beading.[3]The bottom joint must therefore be hammered close; the upper one will become a ledge for the boiler to rest on.[4]In large tools this is not done by the file.

[1]In the drawing, they are all accidentally drawn of the same pitch.

[2]The parts so jointed are highly exaggerated; when hammered down, the joint only forms a light beading.

[3]The bottom joint must therefore be hammered close; the upper one will become a ledge for the boiler to rest on.

[4]In large tools this is not done by the file.

Heroes of the Nations.

EDITED BYEVELYN ABBOTT, M.A.,Fellow of Balliol College, Oxford.

A series of biographical studies of the lives and work of a number of representative historical characters about whom have gathered the great traditions of the Nations to which they belonged, and who have been accepted, in many instances, as types of the several National ideals. With the life of each typical character will be presented a picture of the National conditions surrounding him during his career.

The narratives are the work of writers who are recognized authorities on their several subjects, and, while thoroughly trustworthy as history, will present picturesque and dramatic “stories” of the Men and of the events connected with them.

To the Life of each “Hero” will be given one duodecimo volume, handsomely printed in large type, provided with maps and adequately illustrated according to the special requirements of the several subjects. The volumes will be sold separately as follows:

The first group of the Series will comprise twelve volumes, as follows:

Nelson, and the Naval Supremacy of England.ByW. Clark Russell, author of “The Wreck of the Grosvenor,” etc.Gustavus Adolphus, and the Struggle of Protestantism for Existence.ByC. R. L. Fletcher, M.A., late Fellow of All Souls College, Oxford.Pericles, and the Golden Age of Athens.ByEvelyn Abbott, M.A., Fellow of Balliol College, Oxford.Theodoric the Goth, the Barbarian Champion of Civilization.ByThomas Hodgkin, author of “Italy and Her Invaders,” etc.Sir Philip Sidney, and the Chivalry of England.ByH. R. Fox-Bourne, author of “The Life of John Locke,” etc.Julius Cæsar, and the Organization of the Roman Empire.ByW. Warde Fowler, M.A., Fellow of Lincoln College, Oxford.John Wyclif, Last of the Schoolmen and First of the English Reformers.ByLewis Sargeant, author of “New Greece,” etc.Napoleon, Warrior and Ruler, and the Military Supremacy of Revolutionary France.ByW. O’Connor Morris, sometime Scholar of Oriel College, Oxford.Henry of Navarre, and the Huguenots in France.ByP. F. Willert, M.A., Fellow of Exeter College, Oxford.Alexander the Great, and the Extension of Greek Rule and of Greek Ideas.By Prof.Benjamin I. Wheeler, Cornell University.Charlemagne, the Reorganizer of Europe.By Prof.George L. Burr, Cornell University.Louis XIV., and the Zenith of the French Monarchy.ByArthur Hassall, M.A., Senior Student of Christ Church College, Oxford.

Nelson, and the Naval Supremacy of England.ByW. Clark Russell, author of “The Wreck of the Grosvenor,” etc.

Gustavus Adolphus, and the Struggle of Protestantism for Existence.ByC. R. L. Fletcher, M.A., late Fellow of All Souls College, Oxford.

Pericles, and the Golden Age of Athens.ByEvelyn Abbott, M.A., Fellow of Balliol College, Oxford.

Theodoric the Goth, the Barbarian Champion of Civilization.ByThomas Hodgkin, author of “Italy and Her Invaders,” etc.

Sir Philip Sidney, and the Chivalry of England.ByH. R. Fox-Bourne, author of “The Life of John Locke,” etc.

Julius Cæsar, and the Organization of the Roman Empire.ByW. Warde Fowler, M.A., Fellow of Lincoln College, Oxford.

John Wyclif, Last of the Schoolmen and First of the English Reformers.ByLewis Sargeant, author of “New Greece,” etc.

Napoleon, Warrior and Ruler, and the Military Supremacy of Revolutionary France.ByW. O’Connor Morris, sometime Scholar of Oriel College, Oxford.

Henry of Navarre, and the Huguenots in France.ByP. F. Willert, M.A., Fellow of Exeter College, Oxford.

Alexander the Great, and the Extension of Greek Rule and of Greek Ideas.By Prof.Benjamin I. Wheeler, Cornell University.

Charlemagne, the Reorganizer of Europe.By Prof.George L. Burr, Cornell University.

Louis XIV., and the Zenith of the French Monarchy.ByArthur Hassall, M.A., Senior Student of Christ Church College, Oxford.

To be followed by:

Cicero, and the Fall of the Roman Republic.ByJ. L. Strachan Davidson, M.A., Fellow of Balliol College, Oxford.Sir Walter Raleigh, and the Adventurers of England.ByA. L. Smith, M.A., Fellow of Balliol College, Oxford.Bismarck. The New German Empire: How It Arose; What It Replaced; and What It Stands For.ByJames Sime, author of “A Life of Lessing,” etc.William of Orange, the Founder of the Dutch Republic.ByRuth Putnam.Hannibal, and the Struggle between Carthage and Rome.ByE. A. Freeman, D.C.L., LL.D., Regius Prof. of History in the University of Oxford.Alfred the Great, and the First Kingdom in England.ByF. York Powell, M.A., Senior Student of Christ Church College, Oxford.Charles the Bold, and the Attempt to Found a Middle Kingdom.ByR. Lodge, M.A., Fellow of Brasenose College, Oxford.John Calvin, the Hero of the French Protestants.ByOwen H. Edwards, Fellow of Lincoln College, Oxford.Oliver Cromwell, and the Rule of the Puritans in England.ByCharles Firth, Balliol College, Oxford.Marlborough, and England as a Military Power.ByC. W. V. Oman, A.M., Fellow of All Souls College, Oxford.

Cicero, and the Fall of the Roman Republic.ByJ. L. Strachan Davidson, M.A., Fellow of Balliol College, Oxford.

Sir Walter Raleigh, and the Adventurers of England.ByA. L. Smith, M.A., Fellow of Balliol College, Oxford.

Bismarck. The New German Empire: How It Arose; What It Replaced; and What It Stands For.ByJames Sime, author of “A Life of Lessing,” etc.

William of Orange, the Founder of the Dutch Republic.ByRuth Putnam.

Hannibal, and the Struggle between Carthage and Rome.ByE. A. Freeman, D.C.L., LL.D., Regius Prof. of History in the University of Oxford.

Alfred the Great, and the First Kingdom in England.ByF. York Powell, M.A., Senior Student of Christ Church College, Oxford.

Charles the Bold, and the Attempt to Found a Middle Kingdom.ByR. Lodge, M.A., Fellow of Brasenose College, Oxford.

John Calvin, the Hero of the French Protestants.ByOwen H. Edwards, Fellow of Lincoln College, Oxford.

Oliver Cromwell, and the Rule of the Puritans in England.ByCharles Firth, Balliol College, Oxford.

Marlborough, and England as a Military Power.ByC. W. V. Oman, A.M., Fellow of All Souls College, Oxford.

G. P. PUTNAM’S SONS

NEW YORK27 WEST TWENTY-THIRD ST.

LONDON24 BEDFORD ST., STRAND

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