Glued or butt joints
Glued or rubbed joints. These are used for jointing timber in its width. Lengths up to about 1m can be glued and rubbed only, but cramps are advisable for longer joints. Those to be rubbed should make a close fit throughout their length. At all costs avoid a rounded joint. When pivoted there should be definite friction at the ends. Cramped joints should be shot a trifle hollow and the cramps put in the middle. Alignment across the width should be tested with the straight-edge.
Glued joints are satisfactory for all woods which hold glue well, but other woods should be strengthened as shown. Wood 19mm thick or more can be planed in the vice, but thinner wood unless quite short should be jointed on the shooting-board. Remember that one piece should be face-side uppermost and the other face-side downwards. This ensures the two being in alignment when assembled. Wood 12.5mm thick or more can be glued in the vice. Thinner wood should be rubbed together lying flat on two battens on the bench. Pieces of paper beneath the joint will prevent them from sticking.
For shaped work the coopered joint is useful. It is virtually the same as the plain glued joint, but is at an angle. Wedge-shaped pieces fixed to the shooting-board enable the correct angle to be planed. It is advisable to make a cradle for assembling, this being the inner shape of the job. It ensures the parts being at the correct angle and supports them whilst the glue sets.
Doweled glued joints.
Dowels can be used to strengthen the glued joint. For 22mm wood use 9.5mm dowels, two or more according to length. Countersink the holes slightly and round over the ends of the dowels as at D. The length of the latter should be tested against the hole otherwise they may prevent the joint from going home. A pencil dropped into the hole and offered against the dowel will show this. Avoid a large gap at the bottom of the hole. Note the saw serf to allow surplus glue to escape when the dowels are knocked in.
A simple alternative way of forming the groove in the dowel is to bore a hole of the dowel size in a block of wood and insert a screw at the edge as at Fig. 1 E, so that the point projects at the hole. When the dowel is pushed through the hole the screw point cuts the groove.
Tongued and grooved joint.
This is easily the strongest form of butt or glued joint, but has a disadvantage for some work in that the tongue shows at both ends. Use a tongue about 4mm. (136in.) thick for 22mm. (fin.) wood. Both this and the doweled joint must be cramped. The tongue is cross-grained and should be a hand-tight fit. If too tight it will force open the groove. Plywood is often used for the tongue as it can be cut in long lengths, the grain running cross-wise.
Some workers prefer the method. Countersunk screws are driven into the one piece and left projecting about 10mm.-1 5mm. Holes to receive the heads are bored in the other and slots cut at one side, their width slightly more than the screw shank diameter and about 15mm long. The parts are lightly cramped and the one piece then forced along so that the screw heads bite a channel in the slots. When squaring the screw positions on the edges, the two pieces are staggered by the length of the slot so that the two are level when the one is knocked into position. The joint should be tried together iry and when satisfactory the screws tightened about half a turn before gluing. The cramps should be at a slight angle as shown by the dotted lines so that when the joint is knocked level the cramps are upright.
- A plain glued or rubbed joint;
- B coopered joints;
- C doweled glued joint;
- D enlarged view of dowel;
- E device for forming groove in dowel;
- F grooved joint with loose tongue:
- G end view of tongued and grooved joint;
- H slot-screwed joint.
Dotted lines show cramp positions; I close-up view of screw and slot.
Halving and bridle joints:
- A L-halving;
- B T halving;
- C cross halving;
- D oblique halving.
- E bare-faced dovetail halving;
- F dovetail halving;
- G mired halving;
- H part-mitered halving;
- I mitered bridle;
- J simple bridle;
- K bridle used when top rail lies flat