Part 22 (1/2)

_No. 58. A ledge and miter or lipped miter joint_, Fig. 268, is made by rabbeting and mitering the boards to be joined so that the outer portion of the two boards meet in a miter. It is strong and good looking and may be glued or nailed. It is used for fine boxes.

_No. 59. A stopped miter_, Fig. 268, is useful for joining pieces of different widths, when both sides can be seen.

[Ill.u.s.tration: Fig. 259. Column-Clamp.]

_No. 60. A double-tongue miter_, Fig. 268, is made by cutting on the adjoining edges tongues which engage in each other. It is used in high cla.s.s joinery, on members that join lengthwise of the grain.

_No. 61. A stretcher joint_, Fig. 268, is a slip joint in which one or both sides is mitered. It is used in frames for stretching canva.s.s for paintings by driving wedges from the inside. Two forms are shown in 61a and 61b.

_No. 62. A strut joint_, Fig. 268, is a form of miter joint used in making trusses.

_No. 63 and 64. A thrust joint or tie joint or toe joint_, Fig. 268, is one in which two beams meet at an oblique angle, one receiving the thrust of the other. The toe may be either square as in 63, or oblique as in 64. The pieces are bolted or strapped together with iron. It is used for the batter braces of bridges.

_No. 65. A plain brace joint_, Fig. 269, is one in which the brace is simply mitered and nailed into place. It is used for bracket supports.

No. _66. A housed brace joint_, Fig. 269, is a joint in which the brace is housed into the rectangular members except that the outer end of the mortise is cut at right angles and the inner end diagonally to receive the brace which is cut to correspond. It is much stronger than 65.

_No. 67. An oblique mortise-and-tenon or bevel-shoulder joint_, Fig. 269, is one in which the shoulders of the tenoned beam are cut obliquely and its end is cut off at right angles. The cheeks of the mortise are correspondingly sunk. By these means the tenon prevents lateral motion while the whole width of the beam presses against the abutment. Thus a much larger bearing surface is obtained. The whole is bolted or strapped together. It is used in heavy truss work.

_No. 68. A bridle joint_, Fig. 269, is an oblique joint in which a bridle or ”tongue” is left in an oblique notch cut out of one beam.

Over this tongue is fitted a grooved socket cut obliquely in the other beam. It is used in truss construction.

_No. 69. A bird's mouth joint_, Fig. 269, is an angular notch cut in a timber to allow it to fit snugly over the member on which it rests. It is used in rafters where they fit over the plate.

_No. 70. A plain or rubbed or squeezed or glue joint_, Fig. 269, is one in which the edges of two boards are glued and rubbed together tight. It is used in table-tops, drawing-boards, etc.

To make this joint, first the boards are all laid down flat, side by side, and arranged in the proper order. Three considerations determine what this order is to be: (1), if the grain is of prime importance, as in quartered oak, then the boards are arranged so as to give the best appearance of the grain. (2), if possible, the boards should be so arranged that the warping of each board shall counteract that of the adjacent ones. For this purpose the boards are so laid that the annual rings of one shall alternate in direction with the annual rings of the next, Fig. 280, a, p. 188. (3), if possible, the boards should be so arranged that after being glued together they can all be planed smooth in the same direction. When the above requirements have been met so far as possible, this order should be marked on adjoining edges for later identification. The edges of the boards to be joined should be finished with a jointer.

There are two princ.i.p.al methods of gluing edge-to-edge joints, rubbing and squeezing. In a rubbed joint, the surfaces to be joined should be planed so as to meet thruout exactly. After properly planing one edge of each board, keep one board in the vise, jointed edge up, and place its to-be neighbor in position upon it. Then use these four tests for an exact fit. (1) Sight down the end to see that the faces lie in the same plane. (2) Examine the crack from both sides. Be sure that both ends touch. Test this by pulling down hard on one end of the upper board and noticing if the other end is still in contact. If the other end opens, swing the upper board horizontally on the lower board to see where the high place is and then correct it. (3) See if the upper board stands firmly on the lower board by feeling gently to see if it rocks, or by rapping lightly the lower board. (4) Slide the top board slowly on the lower one to see if it adheres or ”sucks.”

[Ill.u.s.tration: Fig. 260. Applying Glue for an Edge-to-Edge Joint.]

After the pieces have been warmed, which should be done if possible, the glue is spread on them, Fig. 260, and they are then rubbed slowly back and forth in the direction of the grain, pressure being applied by the hand and care being taken not to open the joint in the least.

As the glue sets, the rubbing becomes more difficult. It should be stopped when the boards are in their proper relative positions. In rubbing together the edges of two boards, handscrews may be fastened to one in such a way that their jaws serve as guides for the other board to slide between, Fig. 261. Care must be taken to make the jaws of the handscrew diverge enough not to pinch the upper board.

[Ill.u.s.tration: Fig. 261. Rubbing a Glued Joint.]

Another method is to clamp a spare board alongside and projecting above the lower board. This spare board acts as a guide against which the upper board can be pushed as it is rubbed back and forth. The rubbed joint is especially suitable for short boards.

In joining long boards, a squeezed joint is common. In this case, the edges are planed so as to be very slightly concave from end to end.

The object of this is to counteract the subsequent shrinkage which is likely to take place at the ends of the boards before it does at the middle. The pressure of the clamps may be depended upon to close up the middle, and, especially if dowels are inserted, as in No. 75, the joint will be strong enough to resist the elasticity of the boards.

When the fit is good, warm the wood if possible, prepare the clamps, put a thin film of glue over both edges which are to be together, apply the clamps rapidly, keeping the faces flush, and set away to dry for at least six hours. Then another piece may be added in the same manner. If the boards are thin and wide, and therefore likely to buckle, they may first be handscrewed to cross-strips to prevent their buckling. The cross-strips are, of course, slightly shorter than the combined width of the boards so that the full pressure of the clamps may come on the glued joint.

_No. 71. A rebated, rabbeted or fillistered joint_, Fig. 269. Rebating is the cutting of a rectangular slip out of the side of a piece of wood. The re-entering angle left upon the wood is called the rebate or rabbet. A rebated joint, then, is one in which corresponding rebates are taken off edges so that the joined boards may overlap. It is used in flooring and siding.

A board is rebated and filleted when two adjoining rebates are filled with a fillet.

[Ill.u.s.tration: Fig. 262. Edge-to-Edge Joint, Doweled.]

_No. 72. A matched or tongue-and-groove joint_, Fig. 269, is made by making a projection or ”tongue” in the center of the edge of one board, and a corresponding groove in the center of the other so that they will match together. When used for flooring, the lower side of the grooved board is slightly rebated so that the upper edges will surely touch. This sort of flooring can be blind-nailed.

_No. 73. A beaded joint_, Fig. 269, is similar to a matched joint except that a bead is worked on one edge to disguise the joint for decorative purposes.