Fig. 2429.
Fig. 2430.
We now turn our attention to the flanges, and apply a square to the crown of the box, bringing the edge of the blade fair with the edge of the box, as shown in [Fig. 2428], a representing the box in section, and b the square. Supposing the crown of the box to stand square, as shown in the engraving, and as it should do, we set the brass upon a truly-surfaced iron plate and square up the joint face, as shown in [Fig. 2427], in which a is the surfaced iron, b the brass, and c the square. Since, however, the joint face of the brass may not be parallel with the crown face, we may place the square so that its blade edge comes fair with the crown face—that is, as shown at d in [Fig. 2427]—and set the brass crown (by means of inserting a wooden wedge under its face) truly perpendicular or parallel with the square blade edge. Now try the square with the side face of the brass, setting the latter true with the square blade, as in [Fig. 2430]; a being the iron plate and b the square; and, supposing the box to be true, as it usually is, we may set a scribing-block, as shown in [Fig. 2427], and mark off how much is to come off the flanges by scribing a line around the flange, sufficiently depressing the scriber-point to allow an equal amount to come off each of the flanges. Sometimes, however, the inside faces of the box are not true with the outside face. To test this, we place a straight-edge across the outside face, place a square on it, and apply it to the inside face of the box, as in [Fig. 2429], which is a plan view of the box, a being the straight-edge and b the square. If the square thus applied shows a want of truth in the box, we may set the brass over when adjusting it (as in [Fig. 2427]) to a corresponding amount, and thus mark off the flanges to suit the box.
Fig. 2431.