TENONING, MACHINES. Tenons may be made entirely with saws, or entirely with rotating cutters, or with a combination of both. Where cutters are used, one head may be made to cut a single, a double, or a treble tenon entire, at one operation. Where saws are used it is always necessary to have two sets. To cut a tenon with one cutter necessitates that the stick and the cutter-head shall have relative motion to each other parallel to the plane of the cheek of the tenon ; the cutler projecting over the stick to an extent equal to the desired length of tenon. This motion of the stick or of the cutter-head in a plane parallel with the cheek of the tenon will, if the cutter has the proper outline, cut both checks, both shoulders, and the end of the tenon.
By the use of a single cutter having a central tongue projecting beyond the rest, there may be made a double tenon having no shoulders on the outside, but having any desired amount of shoulder between the two tongues.
Where two entter-heads are used, their axes are parallel with the length of the stick. and the latter is fed in a direction at right angles to its own length and to that of the cutter mandrels. Each of these cutter-heads is practically making a gain or kerf, which has only one side, the side kerf making the shoulder of the tenon. The distance between the cutter-heads determines the thickness of the tenon ; the height of the stick with respect to that of the mandrels, the shoulders. By raising the stick, or both the heads together, the shoulders may be made of the same width, or one wider than the other, with a fixed thickness of tenon. By keeping the stick in a plane parallel to those of the cutter heads, but inclining it so that its length is inclined to those of the cutter mandrels. there may be made a tenon having a bevel shoulder ; but the end will be square with the timber, as for ordinary use, unless the cutters are arranged one in advance of the other, and one of their mandrels bears a cutting-off disk ; in which case there may he made a tenon having both the shoulder and the end beveled to the stick, but parallel to each other.
Tenoning machines producing their work by the action of cutters which remove chips have the advantage of doing work that is smooth in surface and of great accuracy in dimensions, but they consume more power than those which operate by saws. To cut tenons with saws there are required. to produce one double-shouldered tenon at one operation, two parallel mandrels, each bearing a cross-cut saw, and one bearing two ripping saws, the latter mandrel at right angles to the former two and to the stick. To make a tenon with square shoulders, the stick is fed in crosswise, while lying parallel to the mandrel bearing the cross-cut saws, the stick being parallel to them. To produce a double shoulder, it must be fed in askew. The power required to remove two blocks of wood by four saw-cuts is for tenons even of the ordinary width of shoulder less than that needed to cut up into chips the material of the same blocks ; and the advantage in favor of the sawing system increases with the width of shoulder. But it is evident that double tenons cannot be cut with circular saws alone. To mount upon the same mandrel with the ripping saws, a grooving saw, so called, would accomplish the desired result in the same machine, but of course the grooving saw, so-called, is not really a saw, as it performs its work by the utter destruction of the material removed. instead of by taking it out in bulk, with only the kerf as the waste.