Whatever the furniture you make, you will in-variably use one of three forms of construction, or a combination of them: the frame, stool and box. They form the basis of nearly all cabinet construction, and one or more of them can generally be adapted to suit any design. To an extent, however, the matter is complicated by the use of man-made materials—plywood, laminboard and chipboard—which frequently replace solid wood, because the latter is often hard to come by and extremely expensive. The advantage of using man-made materials is the absence of a shrinkage problem, though difficulties may arise if one of them and solid wood are used in the same job, since the one will shrink whereas the other will not. In the case of shaped work it is necessary to use specie! methods.
Systems of construction.
The three are at once clear that the frame can be elaborated to form a door or piece of paneling by the addition of further rails; the stool could become the framework of a sideboard or table; the box might develop into the car case of a chest of drawers or cupboard. All three have been largely evolved to accommodate the two chief characteristics of solid wood: its greater strength along than across the grain, and its liability to shrink in its width. It is because plywood and laminated board are free from these weaknesses that modern construction using these materials is different from the old.
Typical examples of the application of this are mirror frames, paneling, table tops when framed screens, backs and so on. Doors obviously come under the same heading, but these form so wide a subject that they are dealt with separately. Here again man-made materials frequently result in veneered flush doors replacing framed and paneled work.
The point about the framed method is that it over comes the bad effects of shrinkage in timber, at the same time providing strength in both length and width. The panel which might fit in a groove or rebate is free to shrink or swell without affecting the framework, it is never glued unless of plywood or block board, and even then glue is seldom necessary. Strength is ensured by the framework, the grain of which runs in its length along both width and height, so giving rigidity in both directions. Either mortised and tenoned, doweled or mitered joints are used at the corners. As a rule the last named are not so strong and come in for lighter work.
In a sense this may be regarded as four frames put together to form a rectangle in plan, except that there is usually only one post or leg at each corner. Here again the shrinkage problem is overcome as in the case of the frame, and strength is provided in all directions. Items made under the system include tables, chairs, stands and the framework of some cabinets. A point to remember when using the method is that, since wood does not shrink in its length, the resulting car-case will not shrink. Consequently, any solid wood fitted across it such as a top must not be secured rigidly otherwise it is liable to split in the event of shrinkage. It is seldom possible to use anything other than solid wood for such items, except sometimes multi-ply for rails to be veneered. Chipboard is of little use because its strength is low when cut into long narrow strips, and in any case it does not lend itself to strong corner joints. Legs are always in solid wood so that turning, shaping or other work is possible.
- How stool construction was evolved. The method consists of four frames joined together as shown to the left. The same result is achieved by using solid legs.
- Example of box construction in solid wood. The grain direction is arranged so that the whole shrinks together to avoid splitting.
- Faulty construction using solid wood ends and plywood top and bottom. The ends are liable to split as the plywood resists movement.
- Safe construction using ply or block board ends and bottom and solid wood rails.
- Box construction in solid wood. A arrangement for fairly shallow carcase;
- deeper carcase in which small end dovetails prevent curling out of ends;
- chest of drawers construction. The bracket pieces help to keep the ends square.
This is used for all box-like carcases. Shrinkage is no problem because when in solid wood the whole shrinks together from back to front as in Fig. 4. Note that solid wood should not be used in the same carcase as man made materials because the latter would resist the shrinkage of the former and cause splitting. An exception, however, is that narrow solid rails can be used to join ends of such stuff as plywood because shrinkage over such narrow pieces is negligible. Chests of drawers, sideboards, cupboards and any other items built out of solid wood without framing come under the heading. In older, traditional furniture, beneath the main top there was usually a false top of rails with brackets at the ends. Today the top itself frequently forms part of the construction neces-sitting special, and frequently rather awkward joints at the corners。