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In driving nails care must always be taken not to mar the surface of the wood by striking the nail head after it has become even with the surface, as this produces a depression and ruins any fine surface.

The use of the mallet is well illustrated by the making of a mortise-and-tenon joint, the chisel and mallet being used to cut the opening known as the mortise, as shown in Fig. 46.

Patent spiral screw-drivers have come into use in recent years, but where considerable force is required the brace and screw-driver bit are more effective.

It must always be kept in mind that a surface which has been sandpapered has become "gritty," i.e. the fine sand has come off and is more or less imbedded in the wood. Consequently sandpapering must not be done until all tool work has been finished, as the grit will take the edge off the best tool, and the finer the edge the more quickly will it be ruined.

Again, a sandpapered surface is always a scratched surface, and the finest of scratched surfaces cannot compare with the perfectly smooth, satiny surface produced by a sharp plane. However, there are many places where neither the plane nor spokeshave can be used, and here it is allowable to use sandpaper after the tool work has been carried as far as practicable.

Fig. 48 is a case where sandpaper may be used with propriety. The bevels in this lesson are to be chiseled and then sandpapered with a sandpaper block,--the block in this case being simply a small piece of wood with square edges, about which the sandpaper is fastened closely.

Curved articles, such as the hammer handle, must dispense with the block, the sandpaper being held in the hand.

The above method should always be followed in preparing stock for laying out the exercise.

Although the above is the method of laying out a typical joint, each problem will require special treatment and here the student will be guided by his instructor.

When two pieces are fitted together the surfaces of contact are called a joint. There are many kinds and shapes in joinery, and usually some extra fastening is required to hold the pieces together. These aids are glue, nails, and screws; while on heavy construction still others, such as wedges, pins, and dowels are used. The first three are commonly used in small work.

Glue is of two kinds, fish and animal. Both are made from refuse matter,--animal glue being manufactured from such products as bone, horn, hoofs, and hide.

The dry glue in the form of chips must be dissolved in water and heated, being applied while hot. Liquid glues sold in cans ready for use are now very common and require no heating.

In some cases nails are used together with the glue, as at the corners of picture frames. It is customary in this instance to nail in only one direction, as shown in Fig. 53.

Flat-head wire nails, as the name implies, have thin, flat heads, which prevent the nail from being driven beneath the surface.

In a working drawing more than one view is necessary to show the true shape of an object.

In Fig. 57 is shown the mechanical drawing of a cylinder,--the front view, as its name implies, being the image it would make in a mirror held before it vertically, and the top view the image it would make in a mirror held directly over it horizontally.

In making drawings of this kind the greatest accuracy is required and special instruments are necessary.

The drawing board on which the paper is fastened must be perfectly flat, with one of its edges straight.

The T square is used for guiding the pencil or pen when drawing horizontal lines.

The position of T square and triangle when drawing vertical lines is that shown in the sketch, the line being drawn from the T square upward. Horizontal lines are drawn from left to right.

The rule used in mechanical drawing is called a scale, and should not be used for drawing lines. Its purpose is measuring.

All dimensions must be given, and as far as possible they should be so placed as not to interfere with the clearness of the drawing. Neat, small arrowheads and plain, clear figures add to the general appearance, just as does careful lettering in titles and all printed words.

A drawing which is made the exact size of the object represented is known as a full-sized drawing; but for large objects such a method would necessitate large and unhandy sheets of drawing paper. It is customary in such cases to make what is called a scale drawing.

Other scales may be used. In map making, for example, a sixteenth of an inch may represent one, ten, or even a hundred miles. Whatever scale is used, however, the dimensions must always give the exact size of the object represented.

ELEMENTARY WOODWORKING

PART II

WOOD

The lumberman selects trees which have large, straight trunks. They are usually cut with the ax, although the first cut is often made partially through the trunk with a saw. The branches are then chopped off and the body of the tree cut into lengths convenient for handling. They are rolled into a stream and floated down the river to a sawmill, or, in case there is no river near by, are carted on sleds or wagons to the railroad and thence to the mill.

To break up this jam very often requires much labor and great daring on the part of the drivers, who wear spiked shoes and are armed with long poles having sharp steel points. When such a jam breaks up, the crashing of the logs and rush of water can be heard for miles.

The boom consists of logs chained together and stretched across the river just as a fence is built on land to inclose cattle.

The sawmill of to-day is a mass of automatic machinery, and after the log enters it is not touched by human hands until it comes out as lumber of various sizes ready to be loaded on boats or cars.

The number of rings tells us the age of the tree, as a new ring is added each year.

In some woods the difference between the heartwood and sapwood is very marked. In ebony, for instance, the heartwood is coal black and the sapwood white.

After a tree has been cut down the cut end at first looks like Fig. 72. If it is allowed to lie for some time exposed to the weather, its appearance changes to Fig. 74. This is due to the evaporation of the sap, and as there is more sap toward the outside, the shrinkage is greatest there and becomes less toward the center where the heartwood is comparatively dry. This is an important fact to know, because if we had cut the log, while it was still green, into planks, as shown in Fig. 75, the boards would have curled up or warped, as shown in Fig. 76.

When we construct anything in wood we must always consider how the object will be affected by warping and shrinkage, remembering that the shrinkage is only across the grain.

Let us consider the problem of constructing a drawing board to see how warping and shrinkage may be overcome.

The student will find many evidences about the house of how the woodworker has tried to prevent warping and shrinkage, as, for instance, in the paneled doors, tables, etc.

The wood of the various trees differs greatly in hardness, evenness of grain, durability, etc., and every boy should know not only what our woods are used for, but he should also know the trees when he sees them.

We are indebted to the trees for many things besides wood. They give us delightful shade and coolness in summer; many of them produce delicious fruit and nuts; from them we obtain such valuable products as maple sirup and sugar; while tar, pitch, turpentine, rubber, and tannin are only a few of the many tree products. The houses we live in, the chairs we sit on,--in fact, most of our furniture, even to the frames of our pictures, the cars we ride in, and the very pencils we write with, are of wood which was once part of the living forest.

BROAD-LEAVED TREES: THE OAKS

Among the broad-leaved family are such trees as the oak, chestnut, hickory, maples, elms, etc.; and among the evergreens or cone-bearing trees are the pines, spruces, hemlocks, firs, and cedars.

The oak family is a very important one, the wood being hard and strong and the tree a sturdy, healthy, and well-known specimen of tree life.

White oak is perhaps the most common member of the oak family. It grows to a very large size and has a leaf of the form shown in Fig. 79. Observe carefully the outline of the leaf and compare it with the sketch of the next form.

The white oak, like all oaks, bears acorns, and its timber is used as a standard when comparing different kinds of wood. If we say that the strength of white pine is one half, we mean one half that of white oak, and in all timber calculations white oak is the standard, just as the yard and mile are standards of length. In work which requires strength, such as carriage making, shipbuilding, and cooperage, white oak is used very extensively.

The quartered oak used so much for furniture is obtained by cutting the logs in a special manner. The method of cutting gives a beautiful mottled effect with the silver rays spread out in irregular white splashes on a dark background.

We might separate the oak into two distinct groups: those trees whose acorns ripen in one season; those which require two years. The acorns of this latter group remain on the tree throughout the first winter and ripen the second summer.

To the first class belong the white oak just mentioned, the post oak, chestnut oaks, mossy-cup oak, and live oak.

In the second class are the red, scarlet, black, pin, laurel, and willow oaks.

The difference in the leaves of these trees is so great that we need never mistake one for the other. Notice the cut of the red oak and compare it with that of the white oak. The latter has rounded lobes, while the red-oak leaf has sharp points and the fingers of the leaf are indented again with smaller teeth.

The different trees in the white-oak family all have leaves with rounded lobes, and most of those in the red-oak group have pointed ones, yet there is a difference between members of the same family, just as among human beings.

We can tell at a glance whether a man is a negro, a Chinaman, or a white man. If a white man, he may be a Frenchman or an American; and again, if an American, he may belong to the Jones family. But all the members of the Jones family do not look alike and we know one from another.

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