Veneering has become an essential feature of cabinet work today largely because of the shortage of finely figured timbers in solid form, and indeed the shortage of all the hardwoods, quite apart from their prohibitive cost.
In the trade the work is done almost exclusively in a press of one kind or another—indeed many cabinet-makers do not attempt veneering them-selves but give out the work to specialist firms who are equipped for all types of veneering. For the plainer work ready-veneered panels of ply-wood or chipboard are used, the construction being adapted accordingly. These larger firms have presses which not only enable large panels to be veneered but, by the use of resin-based adhesives, turn out the work quickly since these adhesives set rapidly under heat, leaving the press free for further work.
The only press likely to be found in the small workshop is the hand-operated screw type. In using this any jointing in the veneer that may be needed for wide panels or built-up panels such as quartering, is done beforehand and laid as a whole in the press. Many small workshops have no press, however, and the alternative is to use a caul which is cramped down over the surface. It will be realized that not only is a caul larger than the work in hand needed but also a large number of cramps and cross-bearers at any rate when the work is of any great size.
For this reason some workers still prefer to lay veneer by the older hammer method since the equipment needed is simple and inexpensive. The procedure is entirely different in that any jointing is done during the process rather than beforehand. Generally, it is advisable to use the caul or press method for work which is at all complicated. Whatever the method used, however, the preparation of the groundwork is the same.
The plane is used in all directions. It takes out irregularities and gives a key. the shrinkage problem associated with solid wood. On the other hand, the edges have invariably to be lipped and sometimes an edging of solid wood is needed to give a fixing for such items as hinge screws. A rule to remember is that, as far as possible, the grain of the veneer should run at right angles with the outer layer of the plywood or laminboard as in Fig.1 . If this is not done hair cracks may develop in the veneer. When solid wood is used for the groundwork it should be of sound timber, preferably made of strips with the heart sides alternately upward and downward. When a softwood is used any knots should be chopped out and filled with sound wood, and the surface given a coat of size to satisfy the suction of the grain.
First, however, the groundwork should be toothed. This is necessary partly to give a key to the glue, but chiefly to take out any inequalities left by the plane. It will be realized that an absolutely flat surface is essential because any unevenness will be reflected through the veneer. In the case of good-quality plywood or lamin board this may not be essential and it may be enough to go over the surface with coarse glasspaper held over a flat block. Glasspaper only is used over chipboard. Whenever possible both sides of the groundwork should be veneered because veneer tends to pull a surface hollow, and by covering both sides the pull is equalized.
Preparation of veneer.
Veneer is cut with a keen knife or chisel and straight-edge. The latter is not only a guide but serves to hold the veneer flat and-prevent it from buckling or splitting.
- Veneer laid on plywood. Note that the grain of the veneer is at right angles with that of the ply.
- Groundwork made of strips of solid wood, the heart sides alternately upwards and downwards.
- Fig. 3 Preparing surface of groundwork
- How to cut veneer with chisel edge. The veneer must be placed on as otherwise it is liable to splinter out over any irregularities.
and straight-a flat board
- Method of trimming edge of veneer with plane. The veneer should overhang slightly and be pressed down with a straight-edge to prevent it from buckling.
- Parallel strips of veneer cut with the cutting gauge.
- Curved cross-bearers used when caul veneering.
- Order in which cross-bearers are cramped.
- Centre lines on veneer and groundwork to ensure that a built-up pattern or marquetry is positioned correctly.
When it is necessary to trim the edge the veneer is placed on the shooting-board and a batten placed over it to press it flat and hold it firmly. Sometimes several leaves can be shot true simultaneously. When a number of veneer strips are required as for cross-banding, they can be cut with the cutting gauge. The edge of the veneer overhangs as shown and a batten placed on top holds it in position and prevents it from buckling. A cut is made from each side.
When veneers are buckled it is necessary to flatten them first, and this is done by damping and cramping between two flat heated cauls. In bad cases this may be too violent and cause the veneer to crack. An alternative is to damp the veneer with glue size and place between two cauls with a weight on top overnight.
Caul and press veneering. To lay veneer with the caul or in the press the groundwork is given a coat of adhesive and, assuming that resin glue is being used, the glue should be spread evenly with a serrated spreader, preferably followed with a roller. It is then put in the press or the caul is cramped down over it. With a panel of any great size it is advisable to use pairs of cross-bearers with slightly rounded edges so that pressure is applied in the middle first.
For the same reason the centre pair of bearers should be tightened first. The procedure in the case of Scotch glue is similar, but both groundwork and veneer should be glued and allowed to harden. The caul must be thoroughly heated on both sides and cramped down without loss of time. The curved cross-bearers are essential because the glue has to be pressed from the middle outwards. When both sides are to be veneered the work can be done in a single operation, two cauls being used. When there are joints in the veneer as in the case of a built-up pattern all jointing is done beforehand, and the veneers held together with gummed tape applied over the surface. To centre the veneer on the groundwork both should be marked with centre lines and the two sets of lines made to coincide. A couple of veneer pins will hold the veneer in position when being cauled.