Brief mention will be made here concerning the drawing instruments and their use.1
The pencil is of course the draftsman's most useful instrument. Without a pencil of the proper grade, and in good condition, a draftsman can not hope to produce a good drawing. Select the pencil for the work in hand and sharpen it carefully. For sketching use a drawing pencil of grade F; for average drafting work and lettering use an HB or an H and for very accurate work where fine, sharp lines are necessary, a 2H or 4H will serve. The draftsman will soon become familiar with the different grades of hardness of leads and when to use them. Sharpen the pencil to a long tapering point as in Fig. 12, Plate 3, and keep the lead sharp by means of the sandpaper pencil pointer, Fig. 18. It is important that the point be kept sharp, as accurate work can not be done with a broad dull lead. By twirling the pencil between the fingers as a line is drawn, the point will be kept sharp longer than if it were held in one position as it is drawn along. This is an easy and valuable habit to acquire.
This should be a perfectly flat, smooth board of soft wood made in such a way that it can not warp or split. All edges should be perfectly true and smooth. A board 24 by 30 inches is a good size for the student although a smaller one may be used at first.
The T-square, as shown in Fig. 11, is used for ruling horizontal lines only. The head must be held tightly against the left edge of the board thereby keeping the blade in a horizontal position. As the head is slid up or down along the board all positions of the blade will be parallel. Rule against the upper edge of the blade only, and from the left toward the right. A 30-inch blade will work well with the 24 by 30 inch board.
Two triangles will be needed, a 45-degree triangle as shown in Fig. 15 and a 30-60 degree triangle as in Fig. 16. The first is used in conjunction with the T-square to draw 45-degree and vertical lines. The other is for drawing lines at 30 degrees or 60 degrees with the horizontal or vertical. It too may be used to draw vertical lines. Always draw vertical lines from the bottom toward the top of the paper. It will be found that, with these two triangles, one may draw lines 15 degrees apart in any direction.
PLATE 3. INSTRUMENTS.
An irregular or "French" curve, as shown in Fig. 19, is needed for ruling curved lines other than circle arcs.
The architect's scale, which is shown full size in Fig. 27, is one of the most important of the instruments and the beginner will do well to understand it thoroughly before proceeding. As architectural drawings are of necessity much smaller than the objects which they represent, it is necessary to adopt a "short foot and inch" with which to do the measuring on the drawing. So the architect has a scale for this purpose. It is a strip of wood covered with celluloid usually and is divided accurately into spaces which represent feet; these in turn are divided into twelfths, each twelfth representing an inch. Thus one edge is marked off into spaces of 1/8 inch each and each space is considered as being a foot. Then one of these spaces is divided up into twelve parts for the inches. This is called the scale of 1/8 inch to 1 foot and is written 1/8" = 1' - 0". Notice that the mark (") represents inches and the mark (') represents feet. The scale shown in Fig. 27 is divided so that 1/8, 1/4, 1/2 and 1 inch are equal to 1 foot.
If we are to draw a building which is 100 feet long by 50 feet high at the scale of 1/8 inch equals 1 foot, our drawing would be actually 12 1/2 inches long and 6 1/4 inches high. The beginner will have a tendency to think of it in this way which is absolutely wrong and will be found very confusing. Think of each 1/8 inch as being a small foot and use the scale accordingly. Even though the drawing is quite small, think of it as being 100 feet by 50 feet. This will require a mental effort at first but becomes very easy with practice.
1 For a complete discussion consult Reference Books, page 147.
In a similar manner the scale is divided so that 3/4 inch, 1 1/2 inches, and 3 inches each represent 1 foot. Thus a drawing of any object, however large, may be made at a scale to fit the desired size of paper.
The dividers, Fig. 20, are used to step off equal distances or to divide a line or space into equal parts.