Furniture making in this country has its origins going back four or five hundred years to the days when the majority of the population lived in villages or small towns and when one of the principal craftsmen of the community was the carpenter. Chests, settles, tables and sideboard-cupboards were the main items made. Mortise and tenon joints abounded and the most common timber was oak. Decoration, if any, was by relief carving and the finish was oil or beeswax.
Eventually furniture making became a separate craft and English furniture reached its zenith about two hundred years ago in the days of elegant living for the privileged few and miserable poverty for the vast majority.
Most people connected with the furniture industry agree that furniture making went through a bad time in the years between the two world wars. Possibly it was a reflection of the times but the standards of construction, workmanship and finish were regarded as poor. Naturally there were exceptions but the bulk of mass-produced suites during this time were in most cases made with complete regard to a single overriding factor: price. Quality had to suffer.
Most manufacturers of any note now employ trained designers. This fact alone has elevated the standard of much of what we see offered for sale. New materials introduced a few years ago are now well proven, and this is particularly true of man-made boards. Chipboard has possibly been the biggest single influence on the trends in cabinet making, along with melamine plastics surfaces and laminated sheet, or in the form of other synthetic surfaces coated on to a board during manufacture.
Basic forms of construction
Woodworking constructions are generally of three basic types: frame, stool and box. Many are a combination of two forms while others involve all three. Some projects, however, cannot be conveniently classified into any particular type.
The chest is one of the earliest pieces of furniture and in the primitive form was of box construction. This would be made from wide boards, or a series of boards side by side. The earliest jointing would have been by crude nails or wooden pegs. Shrinkage of wood, more pronounced in wide boards, always creates problems. Whichever way the direction of grain was combined there was always a conflict of side grain with lengthways grain. As wood shrinks across the grain, but not lengthways, splits and distortion took place. Over the years techniques have been evolved which make allowance for the fact that solid boards, especially wide ones, are likely to shrink and sometimes swell.
Broadly, shrinkage takes place during seasoning but wood can re-absorb moisture under damp conditions and as a result swell then subsequently shrink again when conditions become drier. This is a very significant factor which has influenced construction methods over the last few years in many specific ways, as we shall explain.
Returning to box constructions, they are to be found a great deal in cabinet making. Although these days material forming the bookshelves may be of veneered chipboard, the use of other man-made boards does not alter the overall style, only the details such as jointing and methods of adding the back. In this example the plinth is shown as an integral part of the assembly.
While hardly an example of cabinet making as such it is another example of box construction. It has four sides and a bottom, and although the sides are narrow it can more conveniently be thought of as a box rather than a frame. It is of box form, even though there are only three sides to the box; rails are introduced as alternatives to the sides.
Most stools and tables are based on stool construction. Broadly, stool construction can be thought of as a three-dimensional framework where the members are relatively narrow compared with the overall size involved.
The cross-sectional sizes of the legs and rails, their positioning in relation to one another and the range of joints and variations to these joints are almost without limit. These factors, along with others such as proportion and shaping, form the basis of designing, and explain why even for a project like an occasional table the number of designs which can be produced is very large.
When cabinet- and chair-making were in their heyday many parts of a piece of furniture were produced by the woodturner on his lathe. Chair legs were often turned for at least part of their length and rails frequently for the whole length, when they were sometimes known as spindles. Using a dowel for a rail is a simplified version of a spindle where, in both cases, the rail is joined to the leg by a hole being bored in the leg to correspond with the diameter at the end of the rail. For both functional and appearance reasons it is possible to use metal tubing such as polished aluminium alloy for the lower rails, which also serve as footrests.
The main part of the sideboard is known as the carcase, and this is of box construction. The same applies to the drawers. The underframing is made up as a separate part and is of stool construction. Before the introduction of plywood and other man-made boards the panels were, of course, made from solid wood, but the construction allowed the panels to shrink or swell without this affecting the job overall, and eliminated the likelihood of splitting taking place. Shrinkage and swelling
The problems associated with the shrinkage of timber during seasoning or drying out were known to early craftsmen but it took time for these difficulties to be overcome. Timber is to some extent hygroscopic. This means it acts in the same way as a sponge and releases moisture to the air during favourable atmospheric conditions, re-absorbing it during very humid
The use of ‘buttons’ for securing a solid top to a table is now a very old established way of holding what can be a quite large area of wood. At the same time they allow the all-important freedom for the top to move, which in a large table could be quite considerable. The small mortises into which the buttons engage are made rather wider than the buttons; this applies especially to the rail which will be at right angles to the grain of the top. Mortises should also be made so that when the button is inserted it is not quite level with the upper edge of the rail. This is to ensure that the screw used to secure the top will hold it tight against the rail. When screwing the top in place the buttons on the rails which are parallel to the grain of the top should not be fully inserted into the mortises, again to allow for free movement.
As a modern alternative to buttons, shrinkage plates can be used. For one, it is necessary to cut a recess in the rail, as shown. The angled type can also be used for other assembly work, such as fixing a plinth to the main carcase.
Where a fairly wide rail is being tenoned into a stile the tenon is often cut with small edge shoulders. Many craftsmen, however, feel it is good practice to cut small edge shoulders wherever this is reasonably practicable, as it always conceals the end of the mortise and makes for a better job.
Edge shoulders are always formed on good quality cabinet work but rarely on softwood joinery. One reason for this is that in joinery the edges of a rail, as shown, would in all probability be either rebated for glass or grooved for a panel. Both of these cuts mean that the edge of the joint becomes hidden anyway. It is often required to fix a batten across the grain of part of a carcase. Here again there is a conflict of grain direction, where solid fixing by glue and screws would almost certainly result in trouble. By making the holes for the screws in the form of slots, the solid side with the screws in it is free to move. This technique is known as slot-screwing. The piece supporting the shelf is usually referred to as a batten, while the upper one, fixed to the top, is called a screw-block.
Half-lap joints can be employed in a number of different forms.
Corner-halving for the corners and T-halving for the intermediate members are the most straightforward. As the name suggests, half the wood is removed on each part of the joint. Where one side of the frame will be visible, the mitre halving has a neater appearance; where there might be a tendency for the frame to be pulled apart the dovetail version has certain self-locking characteristics.
The dovetailed halving is probably the most basic form of dovetail joint. Some craftsmen settle for a 1 in 7 slope for all timbers.
In practice, the bridle would not be used in the type of framing shown as it would leave a very thin ‘neck’ in the rail. The bridle is, however, a useful joint with other applications to be discussed later.
The mortise and tenon joint is the most widely used joint in woodwork. For a joint which is at the corner of a framework such as a door the haunched joint is usual. The haunch is made about one-third the width of the wood, while the thickness of the tenon is one-third, or slightly more, the thickness of the wood. The haunched mortise and tenon has itself a number of varieties. An ordinary through joint is shown at.
A blind mortise and stub tenon joint are really the same type of joint. It is also known as a stopped mortise and tenon. The proportional length of the tenon can vary. For location purposes only, the tenon can be quite short, but for maximum strength the mortise should be cut as deeply as possible without penetrating the member and the tenon made fractionally shorter than this depth. For all blind mortise and tenon joints there should be a slight gap at the end of the tenon in order to ensure tightness at the shoulder.
Hard and fast rules cannot be laid down to decide at what point the tenon in a wide rail should be made into double tenons. The governing factor is the mortise: too long a mortise in a thin member will weaken it, particularly if it is a through joint. Where the width of the wood exceeds about 4 times its thickness, double tenons are used with a centre haunch. The length of a haunch from the shoulders equals the thickness of the tenon. The purpose behind a double tenon is to make the tenon in two parts with solid wood left between them so that strength is not impaired. The tenon is continuous haunched for a shallow depth in order to keep the member ‘in-line’ and provide a clean, tight joint in the finished work.
It is frequently required to rebate the edge of material which is to be mortised and tenoned. The rebate must be allowed for in both parts of the joint. Shoulders of the tenon are not level, the one on the rebated side must be made nearer to the end by an amount equal to the depth of the rebate. The rebate will also cut away part of the tenon, so reducing its width. The extent of the mortise must, therefore, be diminished accordingly. This tenon is said to have ‘long and short shoulders’.
In this case the tenon must be further cut to the form shown at and the mortise made to suit this.
For a panelled frame edges of the material have to be grooved as a means of holding the panels. Here again the joint will be affected. Because it is very much easier to form grooves from end to end wherever this is feasible, the mortise and tenon have to be adjusted to suit. The groove on the rail cuts away part of the tenon, so the mortise is made narrower by an amount equal to the depth of the groove. Because the mortised member is grooved right through, the tenon has to be prepared with a square haunch. This serves to fill what would otherwise be a gap. If so, the tenons and the spaces are made approximately one fourth of the width available. If the groove is narrower than the joint, adjustments have to be made in a similar way as for rebated material.
It is generally considered easier and more straightforward in work of this kind to cut the joints first, then make the grooves or rebates. Rebates in doors and frames are the usual way of supporting and holding glass, bedded in putty and retained by glass sprigs and putty or wooden beads which may be pinned or screwed to the frame.
Sometimes it is necessary to form a mortise and tenon joint on the face of the wood, rather than on the edge. This type of joint is known as twin tenons. Note that the twin tenons are side by side, as distinct from the in-line double tenons.
This provides for a stronger tenon, and therefore a stronger joint. Thus the shoulders are kept quite small to provide a tenon around half the thickness of the member. Stool and box joints
This has a shoulder on one side only. If the tenon were to be positioned in the centre of the rail it would mean that the mortise in the leg would be very near the edge of the wood, thus creating a weak spot. Where two tenons meet at right angles, as they do in a leg of the type illustrated, the usual way of obtaining maximum length for both tenons is to mitre the ends but always so as to leave a small gap between the mitred edges. In the example shown a small edge shoulder is included in the lower edge but it does not matter whether the top haunch is square or sloping.
In work such as small tables and plinths it is often the case that a wide piece of wood has to be jointed to a narrower one.
To minimise loss of strength the trenches need only be fairly shallow but the actual depth would depend on the sizes of the parts being jointed.
Box construction techniques
A wide variety of jointing methods is available for constructions of the box type. Actual choice depends on the nature of the job, amount of strength required and the importance of appearance, to name only three. All the joints shown are suitable for solid wood, but those of an intricate nature, such as the comb joint or the dovetails, are not suitable for chipboard although, with care, they can be cut on plywood. The wood is merely butted together, with the strength coming very much from the nails employed. Ovals, roundheads and panel pins are all used for this purpose but it is usual to slope the nails as shown. This is known as dovetail-nailing and the arrangement resists being pulled apart more than it would if the nails were driven in straight. In any case, nails do not hold so well in end grain as they do in side grain so dovetailing is a good compromise.
The area that can be glued is slightly increased, but again the joint needs reinforcing with nails.
It is wrong to make the tongue too long or too thick as this would result in a weakness between groove and the end of the wood, where splitting could occur because of the short-grain situation. Carefully cut and with a good adhesive, this joint will hold without nails or screws.
It is a joint which is increasing in popularity, partly because it can be quickly cut with the aid of an attachment working in conjunction with a small circular saw, or with a power drill.
The basic principles of the mating slope of pins and tails is that the joint cannot be pulled apart against the slope as, in fact, force applied in this direction makes the joint tighter. For this reason it is quite important on which member the pins should be cut. For instance, they should be made on the horizontal parts of a tool box which has to be carried, and on the front of a drawer. Such joints should always be glued.
In order to conceal the joint on one face, lap dovetails are used. This is the traditional joint for a drawer front and is sometimes referred to as a drawer-front dovetail. The piece with the lap is often thicker than the part with the tails.
Other dovetails which can be used for corners include the double lapped dovetail, where the joint is almost completely hidden and the mitre dovetail, where the completed and assembled joint has the appearance of a plain mitre. Both require considerable skill to make properly.
For both maximum strength and appearance the tongue should have the grain running crossways, when the tongue becomes inconspicuous at the edges. This is a popular type of machine-made joint but can be tedious when made by hand.
As already mentioned, the screws must be slotted if the wood is solid, but this is not necessary with man-made boards.
There is a wide range of metal and plastics devices on the market nowadays, designed to simplify and speed up assembling construction of the type under discussion, especially in the commercial field. Many are of the K.D. type designed for furniture which can be packed flat in a carton and assembled at home. It is a two-part fitting, each half being screwed to the respective pieces forming the joint, then the assembly is held together by a set screw joining the two half blocks.
With many box constructions it is often required to have components which sub-divide the area formed by the four main sides. Trenches of this nature are often made about one-third the thickness of the material.
The stopped trench is used. This is really a combination of a double-stopped trench with mortise and tenons. Details of the arrangement can vary considerably regarding number and position of the tenons, and whether the trench is double or single stopped. This joint is sometimes used as a decorative feature, with the option of inserting wedges of a contrasting colour to secure the tenons.
This combines a great deal of joint applications and furniture-making practice. It can be regarded as typical of traditional techniques, but there are many alternatives depending, for instance, on appearance. Alternatively, small legs could be added to the underside.
Where the top is to be added separately to the main carcase, top rails are employed. The usual method of jointing these to the ends is by dovetailing. Note how the tails are off-centre: this is to prevent the corner of the carcase from being weakened and maybe splitting as a result. It is usual to add a screw through the joint. The back top rail is positioned to be level with the rebate. Screw blocks between the rails serve a double purpose and must be the same thickness as the rails. They act as part of the means of securing the top and also help to control the movement of the drawer. The kicker, which prevents the drawer from tipping when it is pulled out, must never be made a tight fit between rails because an allowance is needed in case of shrinkage.
The rail immediately below the drawer is called the drawer rail and the use of twin tenons is a way often used to joint the ends. Dowels can also be used as a quicker method. Tenons would normally be stopped.
Runners, which are the main components on which the drawer slides, are best if stub-tenoned into the back of the drawer rail. This joint is really for location purposes only, to ensure that the alignment necessary on the top surface for the smooth action of the drawer is achieved.
Cabinets of this nature often contain a shelf, and there are many ways of supporting such a part. There are many fittings available for supporting the shelves. These are often used when there is a need to make the shelf adjustable for height.
A separate plinth is a common feature on small cabinets, and alternative ways of jointing the parts are available. In addition to the ones indicated on the drawing the tongued and mitred joint can be used at the front, and the rear part of the plinth positioned right at the back and jointed by rebating, tonguing or lap dovetails. Often on parts that are completely out of sight, like the inside of a plinth, blocks are glued to the internal corners of the joints to add strength. These are known as ‘glue blocks’.
Note how the dovetail on the front is lapped to conceal the joint, with the pins themselves arranged so as to resist the pull of the drawer. The back of the drawer is positioned to be level with the grooves in the sides, so that the bottom can be slid in after the sides are assembled.
Not shown are the glue blocks usually added to the underside of a drawer. Glue blocks add a lot to the rigidity of a drawer and also increase the area on which the drawer slides.
Plywood is a very satisfactory material for the backs of cabinets. A minor disadvantage of grooving is that there is a slight loss of internal depth. When rebated fixing can be by glue, with pins or screws. Sometimes, to facilitate the finishing process, the back is not actually fixed until the finishing is completed. The back is then screwed or pinned in place.
We now have a great range of adhesives produced synthetically. Many of them are impervious to moisture, and some are boil-proof. Others bond on contact, after first being applied to both mating parts, others even bridge small gaps in jointing surfaces. These are called ‘gap-filling’ adhesives. The subject of adhesives alone is a big one but for general woodworking the many general purpose woodworking adhesives are suitable and makers provide full instructions. They are usually used cold; animal glues generally have to be heated, applied hot and the assembly must be cramped up before the glue cools.
There are some points to be considered when using glues and adhesives: wood is much stronger with the grain than across it, it varies in cell structure and moisture content. These things have an effect on the type of adhesive most suitable for the work.
Face grain to face grain or edge to face and edge to edge produces very strong bonds. End grain is, however, difficult because of the thousands of ends of hollow fibres that are involved. Adhesive must be applied generously to end grain and allowed to soak into the fibrous structure. Dowel joints are a big help with end grain.
When clamping glue joints together while setting the pressure should be firm enough to hold the parts close but not so firmly that all the glue is squeezed out of the joint. Any that does should be mopped away while still wet.