In the last chapter we entered a little upon the matter of dovetails, but
as the mode of uniting the angles of boxes, drawers, and such like, is
of almost universal application, it will be as well to devote a separate
short chapter to the subject.
There are several different kinds of dovetails used, according as it may
be desired to let them appear upon the finished work, or wholly or in
part to conceal them. Carpenters generally use the kind which is visible
on both sides, cabinetmakers, as a rule, take special pains to conceal
it, only using the other form upon work that is to be afterwards covered
with veneer (a thin covering of some ornamental and more expensive wood
glued upon the surface of that which is of less value, and of which the
article is made).
The dovetail described in the last chapter, as proper for the attachment
of the sides to the front of a drawer, is not that which is ordinarily
used by the carpenters, but the following, which is somewhat more easy
to make, and is the same as would be used for the other corners of such a
common drawer as that described.
I must at the outset remind my young readers once again of the standard
rule, without due attention to which they have _no hope of success_ in
this neat and delicate operation of carpentry. _Never cut out your guide
lines, but leave them upon your work_, and use your square diligently
upon the _edges_ of your work, the bottom of the dovetails, sides of the
same, and upon the sides of the pins. Never mind the _time_ necessary for
this. You are doing work, remember, that is to bear inspection,—work that
will stand wear, and be really useful in the household to which you have
the honour to belong. You would not therefore like to see open spaces
here and there, requiring to be filled up with putty, or the side of the
box not truly square to the back and front. And it may be noted here,
that if dovetails are properly fitted together, the box or other article
will stand firm, even before the glue is added; but if the same are badly
cut, and put together carelessly, no amount of glue will avail to hold
the work securely; and it would have been as well or better never to
have attempted dovetailing, as such bad work would be stronger united by
nails, and in any case is but a disgrace to the young amateur mechanic,
whose motto should always be, “_Whatever is worth doing at all is worth
doing well_.”
[Illustration: Fig. 29.]
You will remember how you were taught to wedge up mortice and tenon
joints with glued wedges, which, becoming part of the tenon, and
rendering it larger below than above, prevents it from being withdrawn
from the mortice. Now, a single dovetail has the same effect, and is in
point of fact of the same shape and size as the tenon with its wedges
attached. See Fig. 29, A and B, the first being a wedged tenon, the
second a dovetail.
We shall begin with a single dovetail, which is applied to the
construction of presses used by bookbinders and others, and also
domestically for house-linen. In these there is a strong tendency to
draw the sides upwards, and to tear them from the bottom—a strain which
this form of joint is exactly calculated to withstand. The same is also
used in making many kinds of frames, where similar strength in one
direction is necessary. If you have no special need of such at present,
you should nevertheless make one or two for practice, and to give you a
better insight into their construction. Indeed, if you cannot make single
dovetails well, you will hardly succeed in making a whole row of them
exactly alike, for joining together other articles, as drawers, boxes,
and cabinets. C of this fig. represents a bar of wood truly squared up,
and ready for being marked out. The square is laid across it as seen,
and a line drawn on each side by its assistance, as far from one end as
is the thickness of the other piece to which it is to be attached, and a
little over (say one-eighth of an inch) which will afterwards be neatly
planed off. This is allowed merely because the extreme angles at _e e_
sometimes get damaged in cutting out the dovetail, and if they are, they
will have to be removed. Having drawn the above line all round the piece,
divide it into three by the aid of your compasses, as shown, on what we
may call the front and back, and then on both these sides draw lines, _e
e_, to the angle. You now have the dovetail, or rather the pin of the
dovetail, marked, and with a fine saw you have only to cut out this piece
as you see at D, taking great care to cut accurately close to the lines,
but to leave them, nevertheless, on the edge of the piece you are about
to use.
If you can saw truly, you should not have to touch these pieces with a
chisel, but if not, you must take a _very sharp_ one, and pare the wood
exactly true to the lines which you have marked. Now the dovetail made
by dividing the width of the stuff into three, as given here, will not
answer so well for pine, which is liable to split off in the line H H
of the fig. D; but for ash, beech, elm, and such like, it is a good
proportion. If the material, therefore, is pine, divide it into four
instead of three, as seen at E, and draw lines to the angles from the two
outer marks; or, without any such division, set out equal distances from
each side, so as to give about this proportion to the pieces which are to
be cut out.
Where there are a row of dovetails to be made (as in cabinet work), even
this latter measurement into four would make them too angular, as you
will learn presently. You must now fix upright in your vice the piece
in which is to be cut the dovetail to receive this pin; and laying the
latter in place as it will be when the frame or other work is put
together, draw round it with a sharp pencil or scriber, as seen on the
end of K (the lines _c d_, at such distance from the end of the piece as
is the _thickness_ of the pin, and the perpendiculars, _a b_, are to be
drawn with the square); and if the angles of such pin do not reach the
angles of that in which the dovetail is to be cut, as will often be the
case, the lines on the opposite side similar to _a b_ must be also drawn
with the square. So you see that I was quite right in directing you to
add a square to your box of tools, even before many other requisites of
carpentry.
If it is not considered desirable that the dovetail should reach the
extreme angles of the pieces, as _a b_, fig. K, the pin piece is first
marked as if for an ordinary tenon, and the dovetailed pin marked on
this, as M. When the fellow-piece is cut out, it will then appear as N.
The effect will be the same as the last, except that the end of the pin
will be more conspicuous. A great deal depends upon the material, and on
the intended use of the finished article, therefore you must use your own
judgment, or consult that of others better acquainted with the art than
yourself. L shows the dovetailed joint complete as last described.
[Illustration: Fig. 30.]
We now recur to the row of dovetails and pins—or dovetails and _sockets_,
as the part is often called which is to receive the pins. The most common
kind is that represented by A B, Fig. 30; and as you ought now to be
thinking of a larger tool-box, and would not like it roughly nailed
together like the first, you might try your skill by constructing one
more worthy of the name, and with a drawer or two in it. You must begin,
as before, by marking the two lines across your work by the edge of the
square, or, if you prefer it, by your gauge, which, when set to the
thickness of one piece, will mark the others correctly; and remember to
mark _both sides_. Then set out your dovetails, but do not make them so
angular as you did the single one; for remember you have a whole row of
them to assist in holding the work together, and when glued, this will be
of necessity a very strong and reliable joint, if well made.
Always make the pins before the sockets, and mark round them as closely
as possible, and take great care when sawing not to break them, and if
possible keep their angles also very sharp and clean. It is solely care
in these particulars, and accurate cutting just to the gauge lines and
no further, that makes carpenters’ work generally so superior to that of
amateurs, and boys especially are generally careless, and in too great a
hurry to get the work done, that they may go to something else. Remember,
therefore, that when you begin to hurry your work, you begin to spoil it.
I have made the drawings of the three principal dovetailed joints so
plain as to render special description almost unnecessary after the
remarks already made. The second and third, however, may need a few
words, as they differ slightly from that used in the drawer, of which
a description has been given, chiefly because the piece in which the
dovetails are, is, in this case, as thick as that used for the sockets.
Suppose the dovetails _and pins_ marked out ready to be cut. Take your
marking-gauge and set the slide about a quarter of an inch from the
point, and run a line across the ends of the two pieces at A B, and at C
D, and also at E F. Stop at A B when you cut the sockets, and take care
to get the bottoms of these quite square and even. Cut the dovetails or
pins as directed in making the drawer, but stop on the lines _e f_ and _g
h_ (the latter also to be made with the gauge on both edges of the work),
thus the two pieces will, of necessity, fit nicely together, and only a
single line will appear a little way from one corner. If all lines are
made with gauge and square, this form of dovetail may require neatness
and care, but will not be beyond the skill even of a young mechanic. I
should indeed advise that every opportunity be taken of joining pieces of
wood with tenon or with dovetail, because, after all, these are the chief
difficulties to be encountered. If you can square up your work, and make
true-fitting joints, there is little in carpentry and joinery that you
cannot accomplish.
The third example is worked exactly like the second, but instead of
leaving square the pieces projecting beyond the dovetails and pins,
these are sloped off or bevelled carefully from the extreme corners
down to the pins and sockets. The result is, that when put together, no
joint appears, as it is exactly _upon_ the angle. There is no neater or
stronger method than this of joining the sides of drawers, boxes, trays,
and such like articles. The cabinetmaker employs no other for heavy work;
only when it is very light does he make use of a plan, the appearance of
which is (when finished) like the last-described, but it is less trouble
to make, and less strong, yet sufficiently so for many purposes. This
method is called _mitring_, and is accomplished in the following way.
The wood (let it be for a small tray) is prepared as usual, truly and
evenly, and the ends exactly square to the sides. If you use stuff about
a quarter or half an inch thick, or even an eighth (the first or last
being suitable for such light work), you can make a mitred joint with the
help of the gauge alone, but frequently a _mitre-board_ or _mitre-box_
is used, which saves some trouble in measuring and marking. It is well,
however, that you should begin with this trouble, and take up the easier
method afterwards; especially as it will in this case give you a simple
lesson in mathematics, and teach you some of the properties of the figure
called a square. Let us commence with this lesson.
A, B, C, D, Fig. 31, is a square; the lines at the opposite sides are
parallel,—that is, they are exactly the same distance apart from one
end to the other. To make this clear, E and F are given, which are not
parallel, for they are further apart at one end than they are at the
other. And as A B is parallel to C D, and A C parallel to B D, so A B
is perpendicular to B D and to A C, or what we have called _square_ to
it, as you would find with your square, which is made, as you know, to
prove your work in this respect. The consequence is, that the angles (or
corners) are all alike, and are called right angles. Understand what is
meant by angles being the same size or alike. M and H are alike, though
the lines of one are a great deal longer than those of the other; but
though the lines of K and H are the same length, the angle K is much
smaller than that at H.
[Illustration: Fig. 31.]
As I have gone a little into this subject, I will go a little further,
for it is as well that you should learn all about the sizes of angles,
and I only know of one way in which to make the matter clear.
Every circle, no matter how small or large, is supposed to be divided
into 360 equal parts, called degrees. That large circle which forms the
circumference of the earth is considered to be so divided. Now, if we
draw lines from all these divisions to the centre, they will meet there,
and form a number of equal angles. I have not divided the circle P all
round, because it would make so many angles that you could not see them
clearly; but I have put 360 at the top, and then 45, which means, that
if I had marked all the divisions, there would be 45 up to that point.
Then at 45 more I have marked 90, and so on, marking each 45th division,
and from these I have drawn lines to the centre of the circle. Now, if
you understand me so far, we shall get on famously. Look at the line from
360 to the centre, and that from 90°, and see where they join. This is
a right angle, and this is the angle at each corner of a square. At N,
I have drawn this separately to make it clear, and you see I have taken
a quarter of the circle, or the _quadrant_, as it is called, of 90°.
And you now see that I might extend the lines beyond the circle to any
extent, but it would make no difference,—we should still have 90° of a
circle, only the circle would be larger, as those which are partly drawn
with the dotted lines.
Now, all angles are thus measured by the divisions of a circle; the line
at 45, which meets the line from 360 at the centre, makes with it an
angle of 45°, which is half a right angle. A line drawn at 30° would
make an angle of 30 with the same line from 360, and so on right round;
only when two lines come _exactly_ opposite one another, as 360 and 180,
or 270 and 90, these make _no angles_—they are but one straight line
passing through the centre, and are called diameters of the circle,
a word which means _measure through_, or across the circle. Now, the
corners of a square frame, or of a drawer or box, are right angles of
90°. At R, I have drawn such a corner of a frame, and if I place one
point of a pair of compasses at _e_, and draw a circle cutting through
the lines of the sides of the frame, you see I should make it 90°, or a
quadrant, like N. Moreover, if I draw the sides of the frame as if they
crossed as at _e_ R, I draw a small square, and the line _e_ R is the
diagonal of such square: _e_ R _is the mitred joint I have to cut_. Look
at T S and you will see this, as here the two sides of the frame are
represented as cut ready to be joined together.
A square has another quality: all its sides are equal, and this is very
important, and will help us in cutting out the work. _x_ Y represents the
strip of wood to be properly sloped off for a mitred joint. With a gauge
such as that just above _x_, or your regular marking gauge, set off on
the side Y a distance equal to _x x_ (the _width of the_ pieces); join _x
b_ by a line, and you will have the right slope. Why? Because when you
measured with the gauge you marked the _two equal sides of a square,
and x b is the diagonal of it_, which is exactly the same as you had at
_e_ R. By measuring in this way, therefore, you can, if your strips are
already truly squared up, always mark out a mitred joint correctly. The
two little angles at _x_ and _b_ are also, I should point out, equal—each
half of a right angle or 45°, and the other strip or side of the frame
will make up the other half right angle, or complete the exact square of
90°.
In all this I have clearly laid down the principles of mitred joints,
and given you a lesson in mathematics. I shall now, therefore, go on to
the work of practical construction (Fig. 32). You must be very careful
to make the edge B square to the side A, as in all other work which I
have explained to you; or, if this side is moulded like the front of a
picture-frame, you must square the edge with the back. After having cut
all the pieces, you have to glue them and fasten them together. Warm
them, and use the glue boiling, as directed before, and quickly lay the
pieces together. To do so effectually, you must place them flat on a
board or on your bench, and having adjusted them, you can tie a strong
cord round the whole, putting little bits of wood close to the corners,
so that the string shall not mark your work, if such marks would be of
consequence. Or you can wedge up strongly in another way. If you look at
C you will see a square representing a frame with eight spots round it.
These are nail heads, and mark the position of eight nails driven round
but not touching the frame into the bench. Then, having prepared eight
small wedges, drive them in between the frame and the nails.
You will find this as simple and easy a way of keeping the frame together
as any, and all must remain till the glue is dry and hard—probably till
the same hour on the following day? Then remove the wedges and take up
your frame, which should be trim and strong. Nevertheless, you are now to
add considerably to the strength of it in one or both of the following
ways.
[Illustration: Fig. 32.]
With a mitre-saw or tenon-saw cut one or two slits at each angle, as
seen at D, Fig. 32, _e_ and _f_. Cut little pieces of thin wood, and
having glued them, drive them into these slits. If you saw them slanting,
some tending upwards and some downwards, it will be better than cutting
straight into the frame. Then, when all is dry, neatly trim off these
pieces even with the frame. You may also, if the work is of a more heavy
kind, as a large picture-frame, finish with keyed mitres, _g_. Cut a
place with a chisel of the shape here shown, about one-eighth of an inch
deep, half into one piece and half into the other. Then cut out a key
of the same form of thin hard wood, to fit exactly, and glue it in. The
shape of the key prevents the joint from coming apart, and makes it very
strong and durable. A very large number of light boxes are made with
mitred joints, as workboxes, water-colour boxes, compass-boxes, and such
like; and you can examine these for yourself; but you will not often
see the keys at the angles, because most of such boxes are veneered, or
covered when finished with a thin layer of some ornamental wood.
I shall now proceed to show you how these joints can be cut at once
without the trouble of gauging and measuring to find the proper angle.
Therefore I shall let you into the secret of mitring boxes and mitring
boards, which, if you had much to do of this kind, would shorten your
work considerably.
Fig. 33, A, represents a mitring-board, B a mitring-box. We must go into
a little mathematics again, and try to understand these, because, if you
do so, you may devise others, occasionally more suitable for any special
work you have in hand.
[Illustration: Fig. 33.]
First, look at D of this figure. You have a line, _a b_, standing upon
another C D, and perpendicular to it—that is, it leans neither to the
right nor to the left. It makes two angles at _b_, one on each side of
_a b_, and these are angles of 90°, or right angles, as I explained.
Now, if one line like _a b_ stands on another, these two angles are
_together_ equal to 180°, or twice 90°, whether this line is or is not
upright or perpendicular to the other. Look at fig. C. Here you have the
line _x x_, and standing on it several others; one, _a b_, is upright or
perpendicular, making with it two angles of 90° each, or 180° together.
Now, take _f b_, and suppose this to make 45° on the right-hand side,
you see it makes therefore a proportionately larger angle on the other.
It makes, in fact, an angle of 135°. But 135° added to 45° equals 180°,
which is the same as before, and whichever line you take, the angles
together made by it at _b_ will equal 180° of the circle—that is, they
will equal two right-angles.
Now, if I take the fig. D again, and carry on the line _a b_ right
through _c d_, where it is dotted, two angles will be made on the other
side of _c d_, which will each be right angles of 90° as before, so that
all the four angles thus made are equal. It follows from this, that
whenever any two lines cut each other—E Q and R S for instance—the angles
at T _equal_ four right angles, no matter whether the lines are or are
not perpendicular to each other: and what is more (and what I specially
want you to note), the _opposite_ angles _are equal_—_i.e._, the two
small ones, or the two large ones.
The action of a mitre-block or mitre-box depends upon the principles
here laid down, so you see that although few carpenters understand much
about mathematics, and simply work as they were taught, without knowing
or caring why, those who planned the method of work, and invented
mitre-boards and such like devices to shorten work and lessen labour,
must have understood a great deal about such things. And so it is
generally, as you will find with inventions: things look easy enough, and
natural enough, when we see them every day; but it has taken a great deal
of thought and sound knowledge to invent them in the first place, and a
great deal of practical experience to construct them so neatly. Even a
common pin goes through such a number of processes as would surprise you,
if you have never been able to see them made.
Look carefully at A. It represents a block of wood, about 1½ or 2
inches thick, and 3 or 4 wide, firmly screwed on the top of a board 1
inch thick. The length is about 18 inches. Two saw-cuts are made with a
tenon-saw, right through the block to the board, at angles of 45° with
the line _a b_. These are guides for the saw to work in. The wood to be
cut is laid against the edge of the block, and rests on the board, and
the saw is then applied in one of the grooves while the wood is being cut
by it. Let H be such a piece. If the saw is put in the left-hand slit,
it will cut it like _y_; if in the other, it will cut it the other way,
like _x_; and thus, if a piece is taken off at each end, it will be as
you see, ready to become one side of a frame. Now, examine K, which shows
all the lines or edges of the mitring-board, as seen from above, with
the strip _a b_ sawn across in the line _c a_. The lines _a b_ and _c a_
cross each other, making the opposite angles equal; and as one angle is
45° the other must be 45° also, so that the right-hand side of the strip
is correctly cut. But so also is the other end, and if we turn it over,
it will exactly fit, and the two will form two sides of a square. I could
prove to you that the second strip contains angles exactly similar to the
first, but you ought to be able now to detect the reason for yourself,
and I do not want to teach you more mathematics at present, as I am
afraid you are tired of these, and will want to go on with the real work
of fitting and making. I have, however, said enough, I think, to make you
comprehend _why_ the two saw-cuts must be at an angle of 45° with the
edge of the top board.
Perhaps you wish to make your own board, however, and would like to know
an easy way to get the saw-cuts at the right angle? I shall therefore
show you how to do this, but you must be very exact in your workmanship.
A B, Fig. 34, is the piece of thick board as seen from above, and close
to it is a perspective view of the same which shows the thickness. Set
off a distance, A E, equal to A C, and join C E. The dotted line shows
you that C E is the diagonal of a square, and the angles at C and E
are consequently each 45°; but we do not want this line to end at C,
it is too exactly at the corner for convenience. Measure, therefore,
a distance, E _b_ and C _a_, equal, and join _a b_, which will be the
place for the saw-cut; and the other can be marked out in exactly the
same way. _a x_, in the perspective view, must be carefully marked by the
help of the square. Take care to mark the line on the bottom board, where
the edge of this upper thick piece will fall, and screw the two firmly
together. If the edge and face of the thick piece are not truly square to
each other, the mitres cut thus will not be correct; but, if all is well
made, they may be glued at once together, no paring of the chisel being
necessary or desirable.
The mitre-box, Fig. 33, B, is on precisely the same principle, but is
chiefly used to cut narrow strips not over 2 inches wide; it should be
neatly made of mahogany, half an inch thick. There is also generally made
a saw-cut straight across, at right angles to the length of the box or
board, which is convenient in sawing across such strips of wood, as it
saves the necessity of marking lines against the edge of the square: of
course, it is specially used where a large number of strips have to be
cut square across. In all these you observe one saw-cut leaning to the
right, the other to the left. This is necessary when picture-frames or
moulded pieces have to be cut to 45°, because you cannot, of course, turn
such pieces over and use either side, which you can do when the piece has
no such mouldings.
[Illustration: Fig. 34.]
Several modifications exist of mitring-boards; some arranged for sawing,
and some for planing; and where thousands of frames have to be cheaply
made, the angles are cut off with circular saws, of which I need not
speak particularly here, but which I shall probably have to describe
in a future page. In Fig. 34, K, I have shown one corner of a simple
picture-frame, covered with what is called rustic work, that is—short
pieces of oak, ash, or other wood cut from the tree, left with the bark
on, or peeled and varnished. These are nailed on with small brads; and,
if well assorted and arranged, this will have a very neat appearance,
suiting well for rooms fitted up in oak, as many studies and libraries
are. In picture-frames, however, a rebate (called rabbit) has to be made
at the back, like L, in which the picture with its glass and back-board
has to rest; and this requires a special plane. The front also is always
either sloped off or moulded. I shall therefore make this kind of work
the subject of my next chapter, and describe the operations of rebating,
grooving, tongueing, and moulding.