The next day, as they were about to resume their study, Ralph said:
"There is so much to drawing that I hardly know where to begin, or
what to leave out; but in shop drawing, a picture will not do; imagine
an architect trying to build a skyscraper from a picture. The shop
drawing must tell the mechanic everything he needs to know about the
object he is making. He cannot keep running to the office asking
questions; the drawing must answer them all. That is the reason why the
draughting-room is such an important part of every manufacturing plant.
Drawing is the language the designer uses to tell the workmen what he
wants made. It is doubly important when the designer is hundreds or
thousands of miles away from the workman.
"A battle-ship can be designed in Australia and built in England,
so this language of the shop has grown to be a very interesting and
important art. Every one who works with tools must learn it sooner or
later, the sooner the better.
"Usually it is necessary to represent even the simplest object by at
least two views. For example, suppose I hand you this sketch _a_ (Fig.
23), and tell you to make two out of wood. You wouldn't know what to do
because no thickness is shown, but if I give you this sketch _b_, you
would see immediately that it has practically no thickness and might be
a sheet of paper. You learn that from the top view looking down on it.
[Illustration: Fig. 23. Front and top views]
[Illustration: Fig. 24. Showing necessity for top view]
"The first view is called the front view. Now, suppose I change the top
view to this _c_; thickness is shown here, and if I say, make two of
these out of white pine, you would know all that would be necessary to
go ahead.
"Again, suppose I give you this sketch _a_ (Fig. 24), and ask you to
make two out of gum wood. You would be completely at sea, because that
front view might have any one of these top views shown at _b_, _c_,
_d_, _e_ (Fig. 24). In other words, it might be a triangle without
thickness, a wedge, cone, or pyramid.
"So you see, two views are absolutely necessary, and very often a
third, taken from the right or left side. The three views of a book
would look like Fig. 25. The side view is not necessary in this case,
but that is the way it would be drawn if a third were needed. You will
have plenty of opportunities for practising this as we get along with
our tool work, because in order to understand drawings you must be able
to make them. Suppose you try your hand now, by drawing the two views
of a cylinder, two inches in diameter and three inches high."
[Illustration: Fig. 25. Three views of a book]
Ralph rolled a sheet of paper up until the ends met, to illustrate a
cylinder, and the drawing produced by Harry looked like _a_. (Fig. 26.)
[Illustration: Fig. 26. Mechanical drawings of cylinder and cone]
"Now," said Ralph, "no shop drawing is complete unless it shows all the
necessary dimensions; so I will put them on to show you how it is done,
but after this you must dimension every drawing you make."
The finished drawing of the cylinder is shown at _b_.
Harry was told to make the mechanical drawing of a cone, 2 inches in
diameter, and 3 inches high. While he was working at this problem,
Ralph disappeared, and when he returned Harry asked where he had been.
[Illustration: Fig. 27. Making a tip cat]
"Never mind. Let me see your drawing," _c_ (Fig. 26). "All right." Then
he laid a little wooden object on the table.
"Why, it's a cat," said Harry.
"Yes, a tip cat, and as soon as you make a working drawing of it, you
are going to manufacture one with your knife. Please notice that the
tip cat is a cylinder with a cone at each end, and two views will show
everything about it."
The drawing took longer to make than Harry imagined it would; or it
seemed longer because he was so impatient to get to work with his
knife. His finished drawing is shown at _a_ (Fig. 28).
The different stages in the making of the tip cat are shown in Fig. 27.
[Illustration: Fig. 28. Second tip cat]
First came the squaring up, shown at _a_. Then the two ends were
whittled down to wedges as shown at _b_, and these two ends reduced to
square pyramids, as at _c_.
Lines a quarter of an inch from each edge were drawn on the four sides
of the square part and continued out to the points of the pyramids, as
at _d_. Cutting to this line changed the square to an octagon, and the
square pyramids to octagonal ones.
The edges were again whittled off until there were no more to be seen;
the cat was smoothed with sand-paper, and called finished.
Harry was delighted, but Ralph said: "That is not the best form for
a tip cat, because it will roll. We will make a bat for it now, and
after we have played with it awhile, we'll make a better one; just the
same except that the centre part will be left square and only the ends
rounded." (Fig. 28, _b_.)
The bat they made is shown in Fig. 29. Its handle was cut out with the
coping saw and whittled to the lines. Ralph explained that anything to
be held should be rounded, or it would be hard on the hand, so all the
edges were curved with the knife and finished with sand-paper.
[Illustration: Fig. 29. Bat for tip cat]
They had so much fun with the cat and bat that woodwork was forgotten
for two afternoons. The third day it rained, so the boys were glad to
get at work again in the shop.
Ralph suggested that, as they were doing so much drawing, it might be
well to make a pencil sharpener.
The drawing they produced is shown in Fig. 30. This was easily worked
out in 1/8-inch wood with a piece of sand-paper glued in the oblong
space.
[Illustration: Fig. 30. Pencil sharpener]
The sand-paper suggested match scratchers, and as they are useful
articles, several designs were worked up for Christmas gifts. Three of
these are shown in Fig. 31, but after a good deal of discussion it was
decided that for scratching matches a longer space for sand-paper was
necessary, and three other designs (Fig. 32) were the result of several
hours' work.
[Illustration: Fig. 31. First match scratchers]
"I'm getting tired of match scratchers," exclaimed Harry; "let's make
some toys!"
[Illustration: Fig. 32. Later designs in match scratchers]
"Very well, we'll get ready for Santa Claus, and provide a stock of
things for our numerous young cousins," replied Ralph. "This will give
us a chance to use our coping saw, and I have been wanting to do that
for a long time."
V