No. 38. A pinned mortise-and-tenon is one in which a pin is driven thru holes bored thru the mortised beam and thru the tenon to keep them from drawing apart. It is used in heavy framing as in bridges, in wagon-making, in window-sash, etc.
Fig. 267-38 Pinned mortise and tenon
No. 39. A keyed mortise-and-tenon is one in which the tenon protrudes thru the mortise far enough to receive a removable key and thus be drawn up tight to the mortised member. It is used in work-benches and in ornamental joints like knock-down bookcases and in other mission furniture.
Fig. 267-39 Keyed mortise and tenon
The keyed mortise-and-tenon is made as in a thru mortise-and-tenon, except that before cutting the tenons the holes for wedges should be laid out thus: measuring from the shoulder of the tenon, locate by superposition or measurement the outside of the mortised member. Deduct from this 1⁄16" and square a fine pencil-line across the face and opposite side. This line will be the inside of the hole for the wedge, and the 1⁄16" is deducted to make sure that the key wedges against the mortised member. On the upper surface of the tenon, lay off toward the end the width of the wedge at this point, A B, Fig. 252, and square across. On the under surface, lay off the width of the wedge at this point, C D, and square across.
