Maria E. Ward

“A nut is a piece of metal adapted to screw on the end of a bolt.” “A bolt is a stout metallic pin adapted for holding objects together.” The nut is to the bolt what the knot is to the thread, to keep it from slipping through. Iron and steel are fibrous materials, and very hard; though strong, they are also brittle. Indeed, these metals, and metals generally, resemble molasses candy in their nature more than any other familiar substance that will serve for illustration. When heated, they become soft and liquid; when cold, they are tough, hard, and even brittle. A few powerful, sharp blows with a heavy object are enough to fracture a piece of metal. Direct, heavy blows or tapping on the end of a bolt will flatten and alter its shape sufficiently to cause the edges to project, a very little seemingly, but enough to render it useless.

APPLYING POWER.

If you wish to remove a bolt that seems to fit too tight and resists ordinary methods, place the nut on the bolt, and screw it on level, so that the end of the bolt will be flush or even with the top of the nut. Then lay your piece of wood, quite smooth and flat, on the nut and bolt, covering both, and hammer gently on that with a heavy hammer, with gentle, short, sharp, even strokes. The most obstinate bolt will usually yield to this method of persuasion. Should a burr have formed on the end of a bolt, a file is necessary to remove it; and filing off a burr is a somewhat lengthy and tedious operation.

Unscrew a nut gently and examine it. On the inside will be found a spiral groove and a spiral ridge or thread. Examine the bolt, and observe a similar spiral groove and thread. These, when screwed together, prevent slipping, and the nut cannot be pulled or pushed off. To remove the nut, it is necessary to turn it; and always turn one way, from left to right, if the nut lies uppermost.

To keep a nut from unscrewing by jarring, etc., screw it down until it jams, as it is called, firmly against the surface it rests on. If screwed too tight, it will burst or break the thread, or if enough force is applied the bolt may break. This hardly seems possible until we realize that in the wrench we possess a very powerful lever, capable of destroying quite a large bolt and its accompanying nut. If pains be taken always to start a nut on square and to turn gently and firmly and not too fast, the previous instructions may prove unnecessary.

There are usually two kinds of wrench in a bicycle outfit—an adjustable wrench with sliding jaw, and one or more key-wrenches, so called because made to fit particular parts of the machine, and to be used for them only. The adjustable wrench with sliding jaw should be used with the pressure or pull coming on the angle of the head, and the sliding jaw so placed as to hold its position, the wrench applied so that the greatest strain is taken at the strongest part; then the faces of the jaw keep smooth and true, and will not deface the plating or polish of the machine.

There is another point to note—that a properly adjusted wrench starts a nut easily, while if the strain is taken on the movable jaw of the wrench, there is give enough in the wrench itself to prevent the nut from starting, and the wrench slips off the nut without effecting its object. The handle of the wrench acts as a lever, and the head of the wrench forms a right angle with the handle; it is here that the power is centred, not at the angle made by the movable jaw. Of course, this position seems the reverse of proper until it is analyzed; but once understood and adopted, it will prove most effective.

There are various screws in and about the machine. A screw is defined as a bolt or bar having a thread cut upon it spirally, so that it will enter a hole in which a corresponding spiral groove and thread have been cut, or on which they will be formed by the screw entering the hole. The thread and screw interwind and prevent the screw from being withdrawn unless it is turned. To turn the screw, a notch is cut on one end, which is made flat for that purpose, and the other end of the screw is pointed, to enable it to enter the hole easily. After a screw is placed and started in its proper hole, it is only necessary to turn it until it is driven home. To turn the screw, a short bar is flattened thin to enter the notch on the end of the screw.

The screw-driver should be held and turned with one hand, and steadied and guided with the other. Metal is not so hard but that the leverage of the screw-driver is enough to bend the notches on the end of a screw, and thus render it useless. The question may be raised, Why are not screws made harder? If metal is tempered too hard, it becomes brittle, and flies. A well-tempered screw should be neither too hard nor too soft, but adapted for its particular use or position.

A screw should always be made clean before it is screwed home, any particle of dust or rust being liable to injure the thread and spoil the screw. If the screw is oily or greasy, it will work loose. All screws, bolts, etc., therefore, should be carefully wiped, and never placed where there is any chance for even a little dust to settle upon them. A nut with a small grain of sand inside will burst or break the thread of the bolt.

Bolts and screws are used to hold different parts together or in place and to give strength and firmness.

There is usually an oil-can belonging to every machine, and a bicycle should be provided with a good one, small, light, and easily carried; and special care should be taken that it does not leak. A greasy oil-can is unpleasant to handle and almost useless, as it cannot be handled properly. The least possible amount of oil that can be used is the proper quantity. Greasy bearings only collect dust, and the dust follows the oil back into the friction surfaces, where its presence is always undesirable.

Two kinds of lubricant are used on a bicycle—oil and graphite. A lubricant is used to diminish friction where two or more surfaces move over each other. If these surfaces are of the same material and the same degree of hardness, they do not slip; but the unevennesses of the surfaces engage each other and cause resistance, which produces friction, and friction causes heat, and the parts move more and more slowly, until at last they stop. Now, if a substance of a different character, like oil or graphite, is introduced between the moving surfaces, it forms little cushions, which prevent the two surfaces from coming into close contact; and, as the oil or graphite splits up readily into minute particles, the surfaces slip upon that, instead of holding fast. A smooth surface of metal is full of inequalities, perceptible when magnified, and slipping past each other with as much difficulty as would surfaces of sand paper. Only oil of the best quality and pure graphite should be used. Nothing sticky or gritty in its nature should be allowed near bearing surfaces.

The pump is an all-important and indispensable adjunct of the pneumatic tire. Each tire is fitted with a valve, and accompanied by a pump with which to inflate it. A valve is a lifting, sliding cover, connected with an aperture to prevent the passage of air or other fluids, and so constructed that the pump forces the cover down, and the air pushes past. The cover is held in place by a spring and air pressure, and, fitting tightly against a washer of some soft, impervious material, makes an air-tight joint, and will not move unless displaced. The pump itself is fitted with a valve to fill its cylinder or barrel with air, and to hold the air after the cylinder is full and when the plunger of the pump is forcing the air out of it again. A flexible tube coupling is used to connect the pump-barrel with the valve of the tire.

The valves are of many patterns and sizes, and there are pumps made to fit special tires, and pumps that will in a manner suit almost any ordinary valve. It is most important to note that all the washers about the pump and valves are in place. Deflated tires are often caused by a misplaced washer; and though valves are so constructed that it is not easy to disturb the washers, still it is well to know where they are and when they require attention. Washers wear out and require renewing, and sometimes a defective washer should be replaced; they are usually made of rubber or leather, but metal washers are sometimes used where there is much pressure or friction.

The metal used in bicycle construction must be finished, smoothed, and prepared to resist the corroding effects of the atmosphere and to present an attractive and durable exterior. The metal used for the different parts must be smoothed and polished; all foreign substances, like grease, removed from their surface by a chemical process; and lastly a coating of nickel deposited on the surface by means of electricity. The nickel in this way becomes a part of the original metal, and protects its surface from rust and corrosion. A well-nickeled piece of metal, beautifully polished, and kept free from finger marks, loses its lustre only when neglected. Of course, there are other ways of finishing the surface of the metal parts of the bicycle; other plating metal may be substituted for the nickel, and other finish than polish used.

Light wheels cannot be recommended for rough country or for very fast work over only moderately good roads. A certain weight of material has been taken from the bicycle to make it light; the machine begins to lose its rigidity and consequently its accuracy, and cannot maintain its direction, but wavers, and really travels further to attain a given distance. The weight of a bicycle should depend on the roads it is to cover and the purposes it is to serve. Very light wheels wear out quickly; they cannot stand the strain of practice. Beginners, therefore, should choose a wheel that can endure the handling they will give it.

A very light, well-made, and delicately adjusted bicycle can carry a skilled cyclist anywhere; but a light wheel sooner loses its accuracy, and is then more difficult to work than a heavier wheel that runs true. Heavy wheels are not to be endured; light wheels, too light wheels, not to be encouraged.