Although mitreing is used in everyday woodwork, it comes last in our list of regular joints simply because it has been partly dealt with in almost every previous chapter. For example, we have mitre halving in [Fig. 34], a mitre bridle joint in [Fig. 74], a tongued and grooved mitre in [Fig. 116], mitred mortise and tenon joints in [Figs. 148] and [159], a dowelled mitre frame in [Fig. 202], and a mitred dovetail in [Fig. 286].
| Fig. 321.— Mitred Skirting. | Fig. 322.— Curved Mitre. | Fig. 323.— Halving the Angle. |
Mitreing.—The term mitreing is generally used to denote the type of joint used at the corner of a picture frame; or where two pieces of wood are bevelled away so as to fit each other, as the skirting or plinth mould at [Fig. 321]. In these cases the timber is cut so that the joint is at 45 degrees to the face, and the two pieces, when placed together, form an angle of 90 degrees (a right angle).
The term mitreing, however, is not confined to the fitting of timber around a right angle; it may be justly applied to the fitting of a moulding around an angle irrespective of the number of its degrees.
One often hears such terms as "a half mitre," used to denote the fitting of a moulding around an octagonal column or pedestal, and probably it would be more correct to describe the joint as a mitre cut at 221⁄2 degrees. Mitreing consists of halving the angle and making each piece to fit the line of bisection. Should the angle be bounded by straight lines, as at [Fig. 321], then the mitred joint will be a straight line, but should the angle be bounded by a curved and a straight line, as at [Fig. 322], A, or by two curved lines, then the mitred joint will have to be a curved line if the mouldings are to be of the same section.
Fig. 324.—Sawing Block for Mitreing.
Finding the Angle.—For straight mitres, the mitre joint line is found by bisecting the angle, as shown in the various examples, and the following instructions are given to enable the reader to follow the diagram ([Fig. 323]). Take a pair of compasses, or dividers, and with any convenient opening strike out the arc A, B. Put the point of the compasses on A, and mark another arc C; then, without altering the distance between the points of the compass, put the point on B, and mark the arc D. Draw the line E from the corner, so that it cuts through the intersection made by the arcs C and D. The angle A B is now halved by the line E, and this method may be applied to any angle.
Sawing Block.—For sawing mouldings, etc., to their approximate shape, a home-made sawing block is generally used, as shown at [Fig. 324]. Two pieces of wood are glued one on the top of the other, the required angle is transferred thereto, and the saw kerf made. In the sketch the saw kerfs are shown at 45 degrees, right and left, and other angles and kerfs may be made where desired.