"In taking up mechanical drawing," said Ralph, "always remember that
accurate and neat work, containing all necessary dimensions, is half
the battle. You will probably feel, as I did at first, that it is a
waste of time, but you can always consider that when your drawing is
finished the work is half done. You can judge from it the number of
pieces of stock required, and their over-all dimensions This saves much
time at the wood pile, and tells at a glance to just what size you must
square up each piece of stock.
[Illustration: Fig. 17. The outfit for mechanical drawing]
"The drawing board is an absolute necessity. It need not be perfectly
square, but the surface must be flat and true, and at least one of the
edges absolutely straight. (Fig. 17.) The T square must have a thin
blade--about 1/16 of an inch, and be made of hard wood. It should form
a right angle with the head, which slides along the left-hand edge of
the drawing board, and that must be the straight edge.
"The T square is used as a guide for the pencil in drawing horizontal
lines, and it should always be kept on the same side of the drawing
board. When drawing a vertical line, one of the wooden triangles should
be placed on the T square and the line drawn along the left-hand
edge of the triangle. Circles or arcs of circles are drawn with the
compasses held at the extreme top."
With this introduction, the boys proceeded to fasten with four
thumb-tacks a piece of drawing paper to the upper part of the drawing
board.
"Why don't you put the paper in the centre?" asked Harry.
"Because, if one worked on the lower part of the drawing board, the T
square head would extend below the edge of the board, and touch the
table. You would have to watch it constantly. The head of the T square
should always be tight against the board, for when you slide it too far
down, it sometimes strikes the table without your knowing it, and you
find your horizontal lines are _not_ horizontal; so I always like to
have the drawing paper as high up on the board as possible."
[Illustration: Fig. 18. Blocking out the crosses of St. Andrew and St.
George]
The boys agreed that while the younger was learning to make drawings,
each one should represent something to be made later in wood. Drawing
number one was a square, 3 inches on a side. Ralph showed how this
was made with only two measurements. Drawing one horizontal and one
vertical line, 3 inches were marked off on each, the other two lines
drawn through these new points, and the square was finished. Ralph
insisted that all lines be very light, as they could be darkened up
later, if necessary, and were easy to erase in case of a mistake. (Fig.
18.)
Harry was then told to divide the upper and left-hand sides into even
inches, and to draw across the square vertical and horizontal lines
from the four points obtained.
Thus the large square was subdivided into nine 1-inch squares, and by
darkening the lines shown in the figure at _a_ the cross of St. George
was produced.
Another 3-inch square was drawn, and marked off, as shown at _b_.
The points were connected by oblique lines by means of the 45-degree
triangle, and by darkening the lines shown at _c_ the cross of St.
Andrew was formed. After explaining that the British flag was a
combination of these two figures Ralph said, "While we are drawing
crosses, we may as well make a Maltese one."
Starting with a 3-inch square again, it was measured off as shown
in Fig. 19. The lines were connected and darkened, as shown at _b_.
"Now," said Ralph, "you can cut that out of wood, tie a ribbon on it
and wear it as a medal."
"Huh," grunted Harry. "Pretty big medal--three inches across!"
"Well, make it any size, an inch or even less."
"That's not a bad idea. I'll make it out of white holly, and put a red,
white, and blue bow on it."
"And print on it 'American Order of Junior Woodworkers'."
"Not a bad idea either; we can find lots of boys who would be glad to
join and come here Saturdays to work in the shop."
"There would be no trouble to get candidates; the trouble would be
to take care of them. They would fill the yard and overflow into the
street," said Ralph.
"But why couldn't we----"
"Come now, let's do one thing at a time; you are supposed to be
learning mechanical drawing. We'll leave the organization of the A.
O. J. W. till another time. I'm going to show you how to use the
compasses."
[Illustration: Fig. 19. The Maltese cross]
While they were drawing the circle, quarterfoil, heart, and oval,
shown in Fig. 20, Ralph reviewed his pupil on the meaning of diameter,
radius, circumference, etc. "If you want to cut hearts out of paper or
wood, I would advise you to wait until St. Valentine's Day, and reserve
the oval or egg until Easter.
"The circle is a wonderful figure. By marking the radius off on the
circumference, with the compasses, we find that the former divides the
latter into exactly six equal parts, and by connecting the points, we
have a perfect hexagon. By connecting the alternate points we obtain a
perfect equilateral triangle, and by connecting the remaining points
we get another triangle of the same size. The two triangles form a
six-pointed star. (Fig. 21.)
[Illustration: Fig. 20]
"Now," said Ralph, "I am going to give you a problem by dictation; all
you have to do is to obey orders. First draw a circle 3-1/2 inches in
diameter."
"What's the radius?" asked Harry.
"That's for you to find out."
Harry thought a moment, divided three and a half by two, and setting
his compasses at 1-3/4, drew the circle.
"Now divide the circumference into three equal parts."
[Illustration: Fig. 21. Triangle, hexagon and star]
The boy puzzled over this for a moment, then marked off the radius,
cutting the circumference into six parts, as if for a hexagon, and
erased every other point, leaving three.
"Draw radial lines from these points to the centre."
"Easy," remarked Harry, and drew a line from each point to the centre
with the edge of one of his triangles.
"Find the centre of each of those lines."
"Easy again," said the boy, as he set his compasses at 7/8 of an inch,
and from the centre of the circle cut each of the straight lines with
an arc. (Fig. 22.)
"Draw a semicircle from each of these points with a radius of 5/8 of an
inch."
"Easier still," quoth Harry, as he drew the semicircles. The drawing
then looked like _a_ (Fig. 22).
[Illustration: Fig. 22. Pulley design]
"Now," said the teacher, "let me show you something." He made a few
strokes with the compasses, and the drawing as shown at _b_ was
finished. "That is enough for to-day. The compasses are about the
easiest of all instruments to use, provided you keep in mind that the
pencil point needs to be sharpened to a chisel, or flat shape, the same
as any other drawing pencil. The number of designs which may be made
with it are simply endless, as you will learn later on."