Jointing Machine

“Jointing” a piece of wood or timber, means producing a surface, so that the joint between two pieces that are to come together or be glued shall be close. In order to produce surfaces that shall be true enough for this purpose, it is necessary that the work be held in such a way that it is not sprung or deflected by the holding devices or feeding apparatus.

Fig. 3208, for example, represents a jointing machine, in which the work abuts against an inclined plate p at one end, while the other end is clamped down to the table, which is traversed past the revolving head h, to which are secured two gouge-shaped cutting tools, one of which is seen at t. By using tools of this class, the amount of cutting edge in action is small, and will not therefore spring the work, and if the cutter spindle is adjusted to have no end motion, the work will be true, notwithstanding any slight vibration of the head, because its plane of revolution coincides with the plane of the surface being surfaced or jointed.

In some jointing machines, knives are set on the face of a revolving disc, an example of this class of machine being shown in Fig. 3209, which is for facing the spokes of wheels and for finishing the mitre joint on them.

Three cutters are used, each being set at an angle to a radial line, so that the inner edge of the knife will meet the work first. This gives the knives a shearing cut, and prevents the whole of the cutting edge from striking the work at once. The spokes are placed against a stop on the table, and brought into contact with the cutters by the foot treadle.

The table has beneath it a spiral spring at each end, which returns the table as soon as the foot pressure is released from the treadle. The cutter head or disc is 10 inches in diameter, and should make 2,000 revolutions per minute.

Stroke jointers are machines (such as shown in Fig. 3210) in which a long plane e of the ordinary hand plane type is worked along a slide by a connecting rod c, operated by a crank motion. A machine of this class will do very accurate work, but is obviously suitable for thin work only.

A machine constructed by J. J. Spilker, for cutting mitre joints by hand, is shown in Fig. 3211. The frame a carries a slideway for the slide to which the mitre cutting knife k is secured. The handle g operates a pinion gearing into a rack, which gives vertical motion to the slide and knife. At c is a fence or gauge against which the work is rested, and which is capable of a horizontal motion, so as to bring the work more or less under the knife. For heavy work, the fence c is set back, so that the first cut of the knife will leave the moulding, as shown at h, partly severed, and a second cut is necessary to sever it; for very fine work, a fine shaving may be taken off by a cut taken on the end of each piece separately, after the piece is severed. At d is a graduated scale or rule for cutting the work to exact dimensions, and as its lines are ruled parallel to the right hand edge of the knife k, the inside measurements of a mitre joint may be taken at the outer edge, and outside measurements at the inner end of each line, a set stop at e serving to gauge the pieces for length.