Carcass assembly

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Final assembly of the various component parts is the culmination of many hours of patient work and should never be hurried. A

preliminary assembly in the dry state can be made but only to establish the direction of entry and the exactness of the fit. Dowelled components can be tried with spare dowel-pegs sanded slack (tight dowels should never be used as the suction in a tight hole can hold them immovable), and there can be no objection to fully seating tenons in order to check the shoulders, but dovetails only fit once and should not be entered beyond the halfway mark. If parts of the carcass can be glued, assembled and set aside to dry well before-hand, so much the better; but the squareness must be carefully checked, and if rails or fixed shelving are first glued to the carcass sides both carcass top and bottom should be partially entered to act as spacers. All joints should be clearly marked and readily distinguishable: tenons in chalk or soft pencil on the face of the rail, mortises also numbered on the face, sides marked in bold chalk lettering 'left' and 'right', 'top' and 'base', and other parts according to their location. These precautions might seem needless in straightforward assemblies, but all tenons look alike when covered with glue, and carcass sides have a habit of transposing themselves. A stout hammer and striking-block are necessary, also a long rule for checking opening or the spread of legs, long try-square, squaring-rod for the diagonals and a pair of winding-sticks. Before

Alan Peters Furniture
191 Solid wood carcass construction used on a simple four drawer chest by Alan Peters

the glue is mixed sufficient cramps/clamps should be assembled, tail slides set to the approximate postion and G-cramps/C-clamps likewise, with wood cross-bearers and softening pads for the cramps within reach. If hide glue is used then the component parts must be warmed slightly, but resin glues will set at ordinary room temperatures, giving plenty of time for methodical assembly. Dowelled constructions can have the pegs glued into one side, checked for length and the tops chamfered for easy entry.

192 Detail of a corner dovetail construction

Dovetails Chamfered

Most old craftsmen only kissed the joints with glue, a dab on each tenon and perhaps a wipe across the shoulders, a brushful across the end of dovetails which were then smeared across the pin section, a trickle of glue run into the housings/dadoes. This was deliberate as it saved time applying and time in cleaning up, but the joints did fit and the glue was fairly thick; but with modern glues of low viscosity there is always a danger of starved joints if only a minimum of glue is used and the wood absorbent or the cramping/clamping pressure too great. Moreover, there is no comparison between this day and age and 80 years ago, for furniture must now withstand the ravages of central heating, and so every part should be glued thoroughly. If the surfaces are delicate then a wash coat of white shellac or cellulose can be applied up to but not over the glue-line to protect the surface, and a stick of chalk rubbed across the extreme edge of meeting joints will

Setting up carcasses prevent a dark glue-line showing on pale woods—sycamore, holly, cherry, etc. The actual assembly should be done on a firm and level foundation and the work supported so that it does not sag under the weight of the cramps. Immediately assembly is completed it should be

checked and rechecked for levelness and squareness. Openings should be checked with wood try-square (193:1 A) and set-square (193:lB), carcasses with the squaring-rod (193:2). If the diagonals show a difference of say 1/8 in (3 mm) (193:3) then the carcass will be

1/16 in (1.5 mm) out of square, which could be counted as negligible in a medium or large carcass, but greater disparities should be corrected by tilting the cramps (193:4A, 5A). Flat frames, drawers, etc. should be laid on a level foundation and checked for twist, and if the twist cannot be corrected by tilting the cramps then the high corner should be weighted down, packing up the other corner if necessary to force the twist in the opposite direction. If the carcass has to be cramped across the middle of the width, particularly with fixed shelvings in tight housings, heavy cross-bearers across the sides from front to back should be protected with a pad of newspaper (193:6) to apply the pressure where it is most needed. If a side or top tends to bow inwards it can sometimes be corrected by forcing it to the other extreme as in 193:7 (the distortion shown in 193:4, 6 and 7 is exaggerated for illustration purposes). A close watch should be kept that heavy cramps or cramping pressure do not bow the timber; if so it should be reinforced or the pressure eased a little. After checking from every angle the completed work should be left undisturbed until the glue has set, but heavy cramps should not be left in position longer than necessary or the carcass will tend to sag under the weight.

Carcass backs

Carcass backs can perform three functions: (1) closing in the opening; (2) adding stiffness and rigidity to the carcass; (3) increasing the back weight, thus reducing any tendency for tall carcasses to topple forward when the doors are opened. The thickness of the back and the method of construction will, therefore, depend on the degree of rigidity and the amount of extra weight required, and there is much to be said for the traditional framed-up panelled back, both from the utilitarian and aesthetic standpoints, particularly if solid cedar is used for its permanent moth-repellent properties. Sheet backs of stiff plywood or laminboard are normal and satisfactory, but thin plywood or hardboard are only used in the cheapest work. An additional advantage of the heavy back is its ability to pull a carcass square if for any reason cramping/clamping pressure has distorted it.

The usual form of panelled back is shown in

194:1, 2, while 194:3 is the flush back of ply or laminboard, etc. Backs for pedestal tables and desks can be in individual units (194:4), or taken across the carcass width in a single sheet (194:6) with a bearer rail dovetailed, dowelled or tenoned between the pedestals to support the lower edge. Figure 194:5 shows the construction of the framed back (194:2) with extra wide top rail cut to fit the shaped top; the stiles and rails are normally from 2 in (50 mm) to 3 in (75 mm) wide and 5/8 in (16 mm) finished thickness, according to the size of carcass. Panels can be 3/16 in (5 mm) or1/4 in (6 mm) ply, or 5/16 in (8 mm) or 3/8 in (9.5 mm) solid wood machined to fit the grooves. Haunching of the tenons is optional, and the framing can be dowelled together instead of the orthodox mortises and tenons. In all cases the carcass base is set back to allow the framing to pass over (194:5A). Backs for glued-on tops are shown in 194:7, with the top bearer rail set in and the stiles rebated/ rabbeted into the cheeks or tongued and grooved, as in 194:9. The long edges of the stiles are beaded as shown. Where the top is mitre or double lap dovetailed or tongued and grooved to the sides, and there is no supporting bearer rail for the top of the framing, the rebate can run through (194:8A), but if the top is not mitred (194:8B) then the rebate must be stopped, or a 1/2 in (12.5 mm) by 3/4 in (19 mm) fixing fillet screwed to the underside of the top to form the rebate. Tongued and grooved backs (194:9) are usually rebated into the top, and fixing screws into the rebate are not objectionable if mounted in brass sockets, but the back can be pocket screwed from the inside if preferred. As mentioned before, the carcass base is set back (194:5A).

Types of solid sheet back are shown in 194:11, 12. Veneered carcasses to stand against a wall are not usually edged on the back, but if edgings are provided they must be carefully laid out. Figure 194:13A is a bad placing of the opposing grooves in which the small section beween the tongues (X) will be lost in the machining unless the edgings are glued on before the side grooves are worked, and even then there will be little strength. Figure 194:13B shows the ideal, but if narrow edges are essential they can be offset as in 194:13c and the edges applied before working the side grooves.

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195 Plinths

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  • Steven
    How to build carcases for drawer chests?
    8 years ago

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