Mitre Shooting-Board.—See page 94.
Mitring.—A common joint is the mitre (Fig. 568). Its only advantage is that it shows nothing but a line at the angle and the "end wood" is entirely concealed. It is a weak joint at best, even when made by a skilled workman, and is particularly hard for an amateur to make well. The slightest variation in one of the corners of a frame or box throws the whole structure out of shape and in attempting to correct the error the other joints are apt to be opened, and if the whole is finally got together in a fashion it is often after bother enough to have accomplished much good work in some other way.
Fig. 568.
Fig. 569.
Fig. 570.
The mitre is particularly unscientific for wide pieces used flatways (Fig. 569), as the inevitable expansion and contraction of the pieces is very apt to cause an open joint. If the wood is not quite dry, so that it shrinks, the joint may open permanently toward the inside corner, for when the wood shrinks in width the pieces will become narrower and so separate at the joint, leaving a crack, tapering from the inner to the outer corner. Even if the wood is thoroughly seasoned it will expand and contract more or less. When it expands, the joint will tend to open at the outer corner (Fig. 570). When it contracts it will tend to open, as just shown (Fig. 571), at the inner corner.
