In making picture frames of simple cross section, it is first necessary to cut the rabbet ([Fig. 147]) with a rabbet plane. If this moulding is made by hand, the size of the picture should be measured, the length of all four sides added, and a liberal allowance made for waste.
Fig. 147. Making picture frames
In the figure, the triangles a a are waste, the rabbet being indicated by the dotted line. After the four pieces have been sawed out on the mitre box, they should be placed together on a flat surface, such as the bench top or floor, to see if the mitres fit perfectly. If they do not, one of them can be block planed to make a perfect fit, and the other three laid close together, as shown in the illustration.
The assembling is the hardest part of the operation, and many devices have been tried and some patented to hold the parts together while the glue is drying.
Perhaps the surest way is to drill a hole in one piece of each joint large enough for the passage of a wire bung-head nail.
The undrilled piece is placed vertically in the vise. The drilled piece, after receiving a thin coat of glue, is brought into position horizontally, and the nail driven home.
Theoretically, the nail should catch at the first blow, but the horizontal piece will sometimes slip, even with the best of care. It is wiser to place this piece about 1⁄16 inch above its final position, to allow for this slip.
A method sometimes used is to glue near the ends of each piece a triangular block of wood, as shown at d. These must be left over night to harden.