Basic Construction: Making Tables and Chairs

Construction, size and proportion

If you decide to meet a special need by designing a piece of furniture yourself, base your design on a similar article that you know works well.

Where possible, use timber that is near in size and use the same joints.

Close inspection of the junctions between members in an existing piece of furniture will usually give an indication of the types of joints used. You can confirm your deductions by referring to the descriptions and drawings of joints on:

T-Joints

L-Joints

Mitre Joints

X-Joints

Rebated and Grooved Joints

Dovetail Joints

Examination of Victorian furniture will give a good introduction to the traditional methods of using joints in hand-made furniture — usually in solid timber.

Modern furniture made from block-board, chipboard or flaxboard has machined joints, but these and the way they are used are very closely linked to traditional methods.

Other difficulties in designing furniture arise from size and proportion — these pose problems that professional designers spend years studying.

There is no way of being able to tell exactly what any piece will look like before it is actually made. However, you can save a lot of time and see something of the eventual result by drawing the article full size on a sheet of hardboard, using a set square and a straight-edge.

Use the drawing to work out which joints will be needed, and study similar articles to compare the sizes and positions of various members for proportion and strength.

If you wish to go a little further than a drawing, nail together a mock-up of the piece, using any timber or board to represent the various parts.

Paper stretched over a simple nailed frame can often give a good impression of a chest of drawers or a sink unit front.

A three-dimensional mock-up can be taken into the room where the finished piece is to stand and there it can be compared for size with the pieces around it.

The following examples show ways in which joints are used and combined in furniture construction.

Variations on these methods arc possible, but the most important fact to remember is that this traditional construction, evolved by the work of generations of craftsmen, is tried and known to withstand normal use.

Carcase construction

Carcases for sideboards, cupboards and bookcases are often formed from a basic outer box comprising four panels.

The choice of corner joint depends largely on the material used. Use the carcase joints shown on Three-Way Joints: Fixing Table Legs, or joints that do not involve extra corner pieces.

At top corners use through-dovetail, box or rebated joints, if it does not matter that the joints show. For hidden joints use mitred dovetails on solid timber and loose-tongue mitres on man-made boards. Use mitre joints or lapped dovetails on bottom corners, unless through-joints are acceptable.

carcase construction

When a carcase longer than 750 mm. (2 ft 6 in.) is not supported on an under-frame, a central upright panel is needed. Dovetail housing joints at top and bottom will carry considerable weight.

Use stopped or through-housings for shelves. A drawer support, whether shelf or frame, also needs housing joints.

Back panels

Back panels can be fixed directly to the back of a carcase, screwed into a rebate or held in grooves. In old furniture the back panel is often slid into grooves in the top and sides and screwed to the back edge of the bottom panel or rail.

Make solid panels undersize so that they can expand or contract, but this is not necessary with plywood.

Panelled doors

Use a haunched mortise and tenon joint at each corner of the frame. Mitre joints can be used where no end-grain must show.

The panel, either flat or profiled, can be fitted into a groove in the frame, or the frame can be rebated and the panel retained by a bead.

Make the panel undersize and do not glue it into the grooves. This allows the panel to expand or contract without either it or the frame being forced.

Underframes

The same basic underframe construction is used for dining or occasional tables, stool frames or bases for carcases such as sideboards.

The most important factor in designing a strong underframe is the width of the shoulders on the rails where they join the legs. The wider the shoulder, the greater the strength of the joint.

The best joint to use is the haunched and mitred mortise and tenon. Dowelled and other three-way joints are alternatives, especially when the legs are not very long, as on an occasional table.

underframes

The longer the legs, the greater the need for strength at their junction with the rails.

Corner plates give strength only when the rails are fitted to a firm top panel or carcase.

Shrinkage of timber must be carefully considered when fixing underframes to tops or carcases.

Chairs

Designing a chair that is strong, comfortable and good looking is one of the furniture designer’s greatest challenges.

No other piece of furniture is so dependent for success on its relationship to the user’s physique. The table below lists chair dimensions and angles that designers have found to suit most people.

The chair back can be high or low, provided it supports the sitter in the small of the back. A high back should give support across the shoulder blades and a head rest at the base of the skull. The seat must not give support behind the knees.

chairs

At the junctions of legs and rails, use dowelled or mortise and tenon joints and reinforce them when possible with glued and screwed corner blocks.

Stub-tenon the front legs into the undersides of the arms, or use a bridle joint. Stub-tenon the arms into the back legs. A dowel pin through the side of the arm into the back leg will prevent the arm tenon being pulled out.

29. June 2011 by admin
Categories: DIY Projects, Joints, Woodworking | Tags: , , | Comments Off on Basic Construction: Making Tables and Chairs

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