The Technique of FURNITURE MAKING

Housing/dado, halving and bridle joints

HOUSING/DADO JOINTS

Housings are usually taken to mean wide grooves cut across the grain to receive the full thickness of fixed shelving, drawer runners, etc., although they can also be worked with the grain. Probably the only real difference between a housing and a groove is that the latter is designed to take a shouldered tongue and not the full thickness. Trenches are usually taken to mean seatings or wide housings, but the terms are interchangeable.

Housings/dadoes for fixed shelves can be worked right through or stopped short of the front edge so that they do not show (139:lA), in which case the shelf is notched at the front to allow the remainder to enter. In working hous­ings it is not advisable to rely on measurements exclusively, for the shelf could taper fractionally in the thickness, giving a sloppy fit if the housings were squared across and of constant width throughout. A better plan is to square a pencil-line across the cheek, place the shelf end vertically on the cheek against the pencil-line and scribe the thickness both sides with a sharp knife pressed hard against the shelf. A portable electric router can be used to cut the housings, working against a batten cramped/clamped to the work. Alternatively, if cut by hand, the correct depth is gauged on the back edge, a hole bored at the front to the correct depth, the hole cut out square, the knife-cuts deepened and a small bevel formed to act as a guide for the tenon-saw, the sides sawn down to depth and the waste chopped out with a chisel or routed
away with the hand-router (138). Without a router, or in positions where it cannot be used, a temporary depth-gauge can be made by driving a panel-pin through a block of wood with the point projecting the required depth, as shown in 138. Working the block backwards and forwards will scratch the high spots which can then be levelled.

If the sawing has been accurate the shelf will fit tightly first time, but if not then the sides of the housing/dado must be eased with an edge- trimming plane or chisel. The same setting of the marking-gauge used for the depth must be used to mark the shoulder cut on the shelf which should be sawn in fractionally short of the mark so that the shoulder pulls tight against the cheek when assembled. Housing depths can be about 3/16 in (5 mm) for normal work—and there is little point in recessing more deeply—while the set in from the front edge of the panel can be about 1/4 in (6 mm). The strength of the joint relies on the overall tightness, and a good joint will require knocking home with a hammer and block. Drawer runners in plywood panels need only be recessed about 1/8 in (3 mm) for they can be glued and screwed if necessary, and in any case the loading is up against the side and there is little strain; but drawer runners in solid timber panels will probably require a 3/16 in (5 mm) deep housing for they must not be glued across the grain (see Chapter 21, Carcass construction).

Dovetail housings/dadoes (139:2) are used where there is any considerable side pull, as in tall cupboards, etc., where the side may tend to bow outwards in the length. They can be bareface, i. e. tapered one side (B), or double

(A) , with the former more usual as the bareface at the top helps to keep the shelf square. The dovetail housings are usually cut to rather less than half the thickness of the side and run right through. They can, however, be stopped about 5/16 in (8 mm) from the front edge, which is simple enough with a portable electric router and dovetail-cutter, but more difficult to cut solely by hand. A shaped block (139:4) can be used as a guide for sawing in, and another (139:5) as a seating for chisel cuts to the shelf. Such joints must be tight enough to be effective, yet free to slide across the width of the panel; and as the glue always tends to swell up the fibres, making assembly more difficult, a stopped and tapered (diminished) form (139:3) is sometimes adopted, in which the back portion is an open housing and only the front few inches (100 mm) (B) are taper dovetailed. The taper can run the full length if required (A), but here again the fit is fairly critical, and if too tight the shelf will not travel the full distance. For most normal work there is much to be said for a

straight-sided housing, and, provided it is really tight, infinitely preferable to a badly cut, complicated joint. Simple housing joints can, in any case, be strengthened with the addition of close-fitting blind dowels (139:IB).