Combinations of the various shakes may be found in the same log.
A Few Suggestions about Working-Drawings.—Drawing is far too extensive a subject to be even briefly treated in a manual on wood-working, but a few general remarks on matters connected with working-drawings may be of help to some.
While an ordinary picture gives a correct idea of how an object looks, we cannot take accurate measurements from it. When we need dimensions, as in practical work, we must have some drawings which will show us at once the exact shapes, sizes, and positions of the various parts. In addition to the picture to give us the general idea, we have for working purposes what are called elevations, plans, sections, etc.
In such a case as that of the little house shown on page 242, the picture (Fig. 363) shows us the appearance of the building, but for purposes of construction, working-drawings should also be made. The view of what you would see if you stood directly in front of this house, with only the front visible, is shown in Fig. 364, and is called the front elevation. Stand opposite either side or end, and the view seen is represented in Fig. 364 as the side elevation. In the same manner the rear elevation is given. Next imagine yourself in the air directly above the house. This view is called the plan.[53] In this case, as the view of the interior is desired, the view is shown as if the roof were removed. If the sides or ends are not alike, as is sometimes the case, two side or end views may be needed. In the case illustrated, inside elevations are also given, to show the construction.
Elevations, whether one or several, must always be taken at right angles to the plan. Although commonly, in simple work, confined to representations of each side or end, they can be taken from any point of view that may be at right angles to the plan. They may be taken from the corners or at any angles that may best show any complicated details of the object. If the object is quite simple, one elevation and the plan, or two elevations without the plan, may be quite sufficient, as the elevation or plan omitted can in such cases be understood at once.
Always make your drawings full-sized when the object to be made is not too large. You are much less likely to make mistakes in taking your dimensions and measurements from a drawing the actual size of the object than where you have to take them from a smaller drawing, and you also can get a better idea from a full-sized drawing just how the object will look. It is a safe-guard, with a drawing which is symmetrical, to lay it out from a centre line, measuring to the right and left.
If you make a drawing of which each line is one half the length of the same line in the real object, it is called a "half-size" drawing, and is said to be drawn on a scale of 6" to the foot. If "one fourth size," the scale is 3" to the foot. The scale is often expressed as an equation, viz.: 2 in. = 1 ft., or ¼" = 1'.
If the drawing is not made with accuracy, it is necessary to put the dimensions upon it, and this is often done for convenience and quickness of execution in the case of drawings which are accurate.
Details inside of an object, that is, such parts as cannot be seen or properly shown in the elevations or plan, are often shown by dotted lines, as in Fig. 597. Sometimes dotted lines are used in the same way to show the back of an object, to save making extra drawings. Too many dotted lines, however, are confusing, so if the parts that do not show on the surface are not quite simple and cannot be clearly shown by dotted lines on the plan and elevations, it is usual to make another kind of drawing especially to show such details. This is called a "section" (Lat., sectio, from secare, to cut), and represents what would be shown if the object were cut apart or sawed through at the place where the view of the details is wanted. The surface supposed to be cut is usually indicated by parallel lines crossing the surface, independent parts, as those of different pieces, frequently being shown by changing the direction of the parallel lines, as in Fig. 504.
When both sides of an object are alike, labour and space are often saved by making a drawing of one side or one half only, from a centre line. The same way is sometimes adopted in making sections, and an elevation and section can sometimes be combined in this way in one drawing.