The Technique of FURNITURE MAKING

AREAS OF CARCASS CONSTRUCTION

Carcass construction can be broadly broken down into four main areas, the first being most applicable to present-day large scale production:

1 Knock-down (KD) construction using sheet materials

2 Pre-assembled carcasses from sheet materials

3 Frame and panel, or frame and thin skin construction

4 Solid board carcass construction.

KD construction using sheet materials

Most inexpensive mass-produced carcass furniture is now made from pre-finished plastic coated chipboard, either white, in colour or in simulated wood veneer. In either case, the edges are simply veneered from rolls of the same finishing material and the whole carcass is packed flat into boxes and assembled later, either in the shop or the home, with simple but ingenious KD fittings. Few people realize that of the acres of teak and mahogany furniture that fill our cheaper retail stores, much of it is no more than a paper-thick film of photographed wood protected by a clear plastic coating.

So inexpensive is this pre-finished material and the KD method of construction, that it has

largely replaced the bulky and time-consuming frame and thin panel construction of a decade or so ago for most kitchen and storage furniture in the lower price ranges. Slightly higher in price, but still of the same construction, is KD carcass furniture produced from pre-wood-veneered sheets of chipboard or, occasionally, MDF. These are spray-finished after edge-veneering or, better quality still, after solid edges have been applied.

Carcass assembly with knock-down fittings

KU and KD fittings are described in Chapter 31 p. 291, and 175:1-4 shows a typical particle board wardrobe construction employing these fittings. In practice, these provide rigid fixtures; while any looseness which might develop in use can always be corrected with a screwdriver. They can be used for some solid wood carcass - work, and in fact table shrinkage plates, table brace plates and detachable leg fittings are knock-down fittings in the true sense, but the usual run of KD carcass fittings call for dimensionally stable materials.

Pre-assembled carcasses from sheet materials

In reproduction work and in quality living room and dining furniture, in particular, much is still manufactured, assembled and finished in the factory as complete items of furniture, and it is this area of industrialized construction which is of most interest to the small cabinet-maker. In this area, where veneering and surface finishing are undertaken as part of the production, MDF is fast superseding both plywoods and chipboard as the base material. Its main disadvantage (its considerably increased weight) is far outweighed by its advantages, namely:

1 its dense pre-sanded surfaces;

2 edges that for many purposes require no edging but can be sanded, moulded, stained or coloured at will;

3 no grain direction as on plywoods, so no breaking out across grain;

4 no brittleness or weakness on edges, unlike

176 Jointing methods 1. Mitre and tongue/spline 2. Tongue and lap 3. Tongue and mitre 4. Tongue and groove 5. Housed/dadoed and dowelled 6. Housed & inset tops 7. Dovetail housing

8. Inset tops

particle board, enabling grooving, rebating/ rabbeting, housing/dadoing and edge joints to be cut cleanly and accurately without breaking out or crumbling.

These advantages are obviously just as beneficial to the one-man concern as they are to factory production.

Fig. 176 shows eight basic machine joints for use with sheet materials from 1/2 in (12 mm) thick upwards. Most could also be used, though less satisfactorily, in solid wood instead of the more traditional dovetailing and stub tenoning.

1-4 are all corner joints for top and bottom fixings on flush carcasses, while 5-8 can all be used as alternatives for jointing divisions, fixed shelves, raised bottom panels and inset and oversize tops. It is a matter of choice or of the equipment available whether one stops the joints at the front edge or merely applies solid wood edgings after the joints have been through cut with the spindle shaper or groover. Naturally, the biscuit jointer and portable router come into their own when joints are stopped. Figure 177 shows some of these joints in a very basic construction with an oversize top and separate plinth.

Carcass edging

There is no structural advantage in edging MDF and quality plywood, but particle board and laminboard should always be edged whatever finish is to be applied. The reason for edging MDF and plywood is therefore largely aesthetic, the most obvious example being in order to match face veneers; but if the piece is to be sprayed in colour, this is not necessary at all, although plywood edges would need to be well sealed to prevent the plies showing through.

Solid edges do not require tongues if they are kept to a maximum of 5/16 in (8 mm) thick (Fig. 178); anything above that should be tongued and grooved.

Edge veneering is widely used throughout the furniture industry, but it means near razor sharp and vulnerable edges, and is a practice which is incompatible with quality. It can only be legitimately used in quality work when cross banding is required for decorative reasons, and then the vulnerable edges should be capped with hardwood, either planed flush or left as cock/corner beads.