Cutting The Mortise. It will be remembered that the lines which appear on face B, Fig. 190, have their counterparts on the opposite face D. To cut the mortise, select a chisel having a width as nearly as possible equal to the space between the gauge lines, and, beginning on face B, near the middle of the mortise, advance toward one end, as shown by Fig. 149. The end of the mortise having been reached, commence at the starting point and advance to the other end. Always loosen the chisel by a backward movement of the handle; a movement in the opposite direction would injure the ends of the mortise. (See Fig. 149.) After the first few cuts, each deeper than the preceding, the chisel can easily be made to penetrate an inch or more, in pine or poplar. If the depth is equal to half the thickness of the work, no attention need be given to the chips. One side of the mortise having been cut in this manner, turn the work over and repeat the operation on face D, the chisel being driven down to meet the opening made from the first side. After the cutting is finished, the chips may be dug out with a chisel or driven through by use of a wooden plug. Never try to drive them through by using the chisel with its cutting edge parallel to the grain, as such use is very likely to split the work. The chips having been removed, the truth of the mortise may be tested by using the flat side of the chisel as a straightedge, as shown by Fig. 192. The sides of the finished mortise should agree with the chisel, as at a. Compare a with b. Remember that at least one-half the thickness of the line should remain on the work.

Fig. 101 Scale, 3"=1'

Side.

End.

166. The Tenon may next be cut by using the back-saw, both across the grain and with it. The sawing, if to line, leaves nothing to be done except the pointing of the tenon; this is accomplished by a stroke of the chisel on each side, which makes it appear as shown by Fig. 193. The pointing is necessary, because a square-ended, tight-fitting tenon, if driven to place, will splinter the sides of the mortise. The length of the tenon is sufficient to make it project beyond the mortise a distance more than equal to the part pointed. After the fitting has been done, the projecting part is cut off.

When both the mortise and tenon are finished, cut the piece on the line c, Fig. 190, and try the tenon in the mortise. It should enter at a light-driving fit. If the shoulders of the tenon do not make a good joint with the cheeks of the mortise, that is, if the joint at S, Fig. 191, is not good, it may be sawed to a fit, as in the case of the splice. When all is satisfactory, bore the pin hole, insert the pin, cut off the projecting portion of the tenon and of the pin, and take a light shaving from those surfaces on which a plane may be used.

Fig. 192

Fig. 103

Plan.

Elevation.