Fig. 126.—Tongueing Shoulders of Tenons.
[Fig. 126] shows the method of tongueing the shoulders of tenons as used in thick timber which is to be veneered on the face. A temporary piece of wood (A) is put between the tenon cheek and the saw, thus forming a guide for the latter. After cutting one saw kerf a thicker piece is made and a second saw kerf cut; the waste between the saw kerfs is now removed with an 1⁄8 in. chisel and this completes the groove. A tongue of this type acts as an extra tenon and prevents the joint from "lipping" (becoming uneven) on the face side.
THE MORTISE AND TENON JOINT
A mortise and tenon joint is the method of joining timber by working a solid rectangular projection in the one piece and cutting a corresponding cavity to receive it in the adjoining piece. The projection is called the tenon, and the cavity the mortise. Joints of this type are secured in various ways. Small wedges, wooden dowels, metal dowel pins, glue and paint are frequently used, and prior to the introduction of glue we have examples of Egyptian furniture in which the mortise and tenon joints were united by a composition of cheese.
| Fig. 127.—Barefaced Tenon Joint. | Fig. 128.—Stub Tenon. |
Barefaced Tenons.—[Fig. 127] illustrates the joint in its simplest form and shows a tenon having only one shoulder. This is called a barefaced tenon, and it will be noticed that the portion which carries the mortise is thicker than the rail on which the tenon is cut. The joint is therefore level (or flush as it is called) on one side only, and it should never be used at the corner of a frame. It is a useful interior joint for framing that has to be covered on the back side with matchboarding, and allows the work to finish level at the back when the boarding has been applied (see plan, [Fig. 127]).
Stub or Stump Tenon ([Fig. 128]; also occasionally called a joggle tenon).—The illustration shows a tenon as used in the interior of a frame. The tenon is not allowed to run through the stile, and unslightliness on the edge is thus avoided. This type of tenon is often used at the corner of a frame, and it then requires to be haunched. A good workshop method of gauging the depth of the mortise for a stub tenon is shown in [Fig. 129]; a piece of gummed stamp paper is stuck on the side of the mortise chisel, indicating the desired depth of the mortise. This greatly facilitates the work, as it is not necessary to be constantly measuring.
A Haunched Tenon as used at the end of a door frame is shown at [Fig. 130].—In this case it will be seen that the width of the tenon is reduced, so that sufficient timber will be left at the end of the stile to resist the pressure of the tenon when the joint is driven together. The short portion (A) which is left on the tenon is called the haunch, and the cavity it engages is termed the haunching. The haunch and haunching prevent the two pieces of timber lipping, or becoming uneven on the face side, as would be the result if it were cut away entirely up to the shoulder.
[Fig. 131] shows the type of tenon and haunch used when the stile or upright rail is grooved to receive a panel. In this and similar cases the haunch is made the same width and the same depth as the groove; the groove therefore acts as the haunching. An application of this joint is shown in the top rail of the door frame, [Fig. 132].