[Illustration: Fig. 31.]
[Illustration: Fig. 32.]
It will now be in order to show how the square can be used for getting
the lengths and bevels for braces of regular and irregular runs. If we
wish to lay out a brace having a three-foot run on both post and beam,
the matter is quite simple, for we can take 12 inches on the tongue and
12 inches on the blade and transfer this distance three times on a
straight line and we have the extreme length of the brace from point to
point, and by marking along the blade at one end of this length and
along the tongue at the other end we also get the bevels. This is easy
and simple enough, and without further refinement will give the lengths
and bevels exactly for a flat-footed brace. When the run is different
than the rise, as in the example shown at Fig. 31, the square is applied
in a somewhat different manner. Here we have a run of three feet and a
rise of four feet. To get the proper length and bevels for a brace to
fit in this situation we must use 12 inches on the tongue and 16 inches
on the blade, then the bevel of the upper end of the brace will be found
along the line of the tongue, and the line of the blade will give the
bevel for the foot of the brace. In this case the square is transferred
three times, just as though the rise and run were both three feet; the
difference being made by dividing the odd foot into three equal parts of
4 inches each and adding one part to the blade, thus making the gauge
point on the blade 16 inches instead of 12 inches, which regulates the
extra length and the change in bevels. A little study on the part of the
reader will reveal to him how the square may be set to gauge points so
as to make a brace suitable for any rise and run of any right-angled
frame work.
A brace intended for equal run and rise of four feet is shown at
Fig. 32. Here we have the fence in use, and the square is shown in all
its positions from start to finish in the formation of the brace. The
gauge line marked _0000_ is the line from which the marks 12 and 12 are
supposed to measure, and this when squared over as shown leaves a butt,
or “heel of the brace,” which is to rest on a shoulder “boxed” in both
beam and post. The dotted lines on the ends of the brace show the tenons
for which mortises are made in both post and girt or beam. It must be
understood, of course, that this operation is only performed once for
each kind of brace, and that on a pattern made of some kindly wood, such
as pine, cedar or whitewood. For the pattern, dress up a piece of wood
to 4 inches wide if the braces are to be made of 4x4-inch stuff; if for
larger or smaller stuff then make the pattern the width of brace to
suit. Have the pattern of sufficient length; if for a 4-foot run and
rise it will require to be not less than 6 feet long. Run a gauge line
three-eighths of an inch from the straight or front edge, as shown at
0000, and set the two 12-inch marks on this line, then screw the fence
tight on the square with its sliding edge against the edge of the
pattern, and then slide and mark as shown four times, when the length
and bevels of the brace will be obtained. Provide for the tenons beyond
the lines shown by the square, or for a “flat-foot” brace, saw the
timber off on the lines shown on the edge of the square. After the
pattern is made the fence and square may be laid aside, as the pattern
can be used for any number of braces, and when finished with on one job,
may be safely placed away to use again for the same “run and rise” when
occasion arises. The pattern may be any thickness from half an inch to
one inch. The same rules may be observed in making patterns for any
regular or irregular runs and rises.
With regard to the _brace rule_ as given on steel squares, I may say
that there is some slight difference in the lengths given by different
makers—though nearly all modern makes figure up alike—but this
difference is so small that in soft wood framing it has no effect. In
hardwood framing the framer never applies these rules, but gets his
lengths with the square and fence.
The length of any brace simply represents the hypothenuse of a
right-angled triangle. To find the hypothenuse, extract the square root
of the sum of the square of the perpendicular and horizontal runs. For
instance, if 6 feet is the horizontal run and 8 feet the perpendicular,
6 squared equals 36, 8 squared equals 64, 36 plus 64 equals 100, the
square root of which is 10. These are the figures generally used for
squaring the frame of a building or foundation wall.
If the run is 42 inches, 42 squared is 1764, double that amount, both
sides being equal, gives 3528, the square root of which is, in feet and
inches, 4 feet, 11.40 inches.
In cutting braces always allow in length from a sixteenth to an eighth
of an inch more than the exact measurement calls for.
Directly under the half-inch marks on the outer edge of the back of the
tongue will be noticed two figures, one above the other. These represent
the run of the brace, or the length of two sides of a right-angled
triangle; the figures immediately to the right represent the length of
the brace or the hypothenuse. For instance, the figures 36-36 59-91 show
that the run on the post and beam is 36 inches, and the length of the
brace is 50.91 inches.
Upon some squares will be found brace measurements given where the run
is not equal, as 18-24 30. It will be noticed that the last set of
figures are each just three times those mentioned in the set that are
usually used in squaring a building. So if the student or mechanic will
fix in his mind the measurements of a few runs, with the length of
braces, he can readily work almost any length required.
Take a run, for instance, of 9 inches on the beam and 12 inches on the
post. The length of brace is 15 inches. A run, therefore, of 2, 3, 20,
or any other number of times the above figures, the length of the brace
will bear the same proportion to the run as the multiple used. Thus, if
you multiply all the figures by 4 you will have 36 and 48 inches for the
run, and 60 inches for the brace, or to remember still more easily, 3, 4
and 5 feet, or 6, 8 and 10 feet.
There are other runs that are just as easily fixed in the mind. 51-inch
run, brace 6 feet, 12 hundredths of an inch; 8 feet, 3-inch run, brace
11 feet, 8 inches, etc.
The following examples and explanations on roof framing are simple and
easily understood, and cannot fail of being valuable to the young
mechanic who aspires to become an expert roof framer. These examples
will serve as starters, and in the following volume, which will be
issued shortly, more advanced examples will be presented.