s.

A dado joint, Fig. 266, No. 25, should not be so deep as to weaken the
supporting board.

A tenon should not be so large as to weaken the mortised piece.

Pins or other fastenings, Fig. 267, Nos. 38 and 39, may weaken rather
than strengthen a joint if they are so placed or are so large as to
shear or crush their way thru the timber.

9. _Place each abutting surface in a joint as nearly as possible
perpendicular to the pressure which it has to transmit._

Illustrations of this principle are as follows: the angle in a strut
joint, Fig. 266, No. 62, should be equally divided between the two
beams.

The thrust joint, Fig. 268, No. 63, in a bridge truss, is exactly at
right angles to the pressure.

It is on account of this principle that a spliced joint for
compression, Fig. 264, No. 4, is different from a spliced joint for
tension, No. 5; and that a housed braced joint, Fig. 269, No. 66, is
better than a plain braced joint, No. 65.

A joint to resist vertical cross strain is stronger when scarfed
vertically than horizontally.

THE PRINCIPLES OF JOINERY

REFERENCES:[*]

Goss, p. 132.
Adams, p. 12.
Rivington, Vol. I, p. 57.

[Footnote *: For general bibliography see p. 4.]

CHAPTER X.

WOOD FINISHING.

STAINS.

The function of stains is to change the color, and to enchance the
grain and texture of the wood. Stains may be divided into four general
classes, which are not, however, entirely distinct. (1) Oil stains,
(2) Water stains, (a) made from anilines, (b) made from dyes other
than anilines, (3) Spirit stains, (4) Stains due to chemical changes.

(1) _Oil stains._ Advantages: they are easily prepared, are easy to
apply evenly, and they do not raise the grain. Disadvantages: they
cover the grain somewhat, are apt to give a muddy effect, they do not
penetrate very deeply into the wood, and it is impossible to stain
hard wood dark with them and at the same time keep the grain and
texture of the wood clear. A convenient form in which to handle
these pigments is Devoe's "coach colors," ground in japan. To prevent
evaporation from cans once opened, it is well to keep them partly
filled with water and the water covered with a little oil. For use,
the pigments are thinned with turpentine or benzine, in the proportion
of one pound of color to one-half gallon of turpentine or benzine.
Benzine is much cheaper than turpentine, but evaporates more quickly.
The addition of a little