Basics of Woodworking

Materials

Tree growth is a very complicated subject but a simplified explanation of the structure of a tree is helpful in understanding what wood grain is, why boards warp, and the difference between softwoods and hardwoods.

Tree growth

Wood is basically made up of bundles of elongated cells much like drinking straws. It is through these cells that the nutrients from the soil and water travel from the roots of the tree through the trunk to the branches and leaves. The tree trunk consists of the outer hark, a layer of young, lighter coloured wood called sap­wood, and the central core of darker and harder wood called heartwood.

ABOVE: The annual growth rings in this cross-section of a log indicate the age of a tree. The outer, light rings are the younger sapwood through which the tree gets its nourishment: the darker and more dense heartwood is the older growth of the free. Just inside the bark is the layer of cells pulled the cambium.

Each year during the growing season, the tree acids a new layer of wood just inside the bark. As more sap rises in the spring, the wood produced then has larger, softer cells. This light-coloured wood is called spring wood. The wood which grows during the summer is denser and darker in colour. This difference in colour between spring and summer wood produces the rings to be seen in the cross section of a log, and counting these annual rings reveals the age of the tree.

In general, trees which grow quickly produce wider growth rings and the wood is therefore softer and coarser than that of trees which grow more slowly. Pine, which is a softwood, is inexpensive compared to mahogany, which is a slow growing hardwood.

Identifying and choosing wood

Woods can be identified by their grain pattern, colour and even their smell. Some pines, such as Pitch pine, have a strong resin smell. Cedar has a fresh scent which tends to keep away moths and is therefore ideal for making drawers and chests to store wool clothing.

The hardness and grain pattern is usually an important consideration. Generally, the denser or heavier the wood, the harder and more durable it will he. The grain pattern, however, tends to vary from one piece of wood to the next and should be chosen carefully.

The colour of the wood is also a consideration in deciding which type to use for a particular job. Wood colours vary from the almost pure white of sycamore and holly to the black of ebony, and range from the yellow woods like pine and boxwood, red woods like mahogany and rosewood and the rich browns like walnut and chestnut.

In the end the most important consideration is usually money. Softwoods are fairly inexpensive and widely available in a variety of sizes. Hardwoods like mahogany tend to be much more expensive and are available only at the larger timber merchants.

Cutting up timber When a tree is felled it is usually first sawn into planks so that it can he dried evenly and quickly. There are various methods of cutting tip the log to produce the maximum- amount of good quality timber. Nowadays, the whole tree is used.

The bark is used for fuel, the sapwood for veneers or for timber, and the heartwood for timber or for chemicals such as turpentine, pitch and tar. Even the chips and sawdust that are produced by cutting up the logs are used to make sheet materials like chipboard and hardboard.

Drying timber

There is a considerable amount ofmoisture in a tree. The weight of the sap can make up to half the weight of the wood. As the wood dries out, it shrinks in width, sometimes up to 10%, and the timber can be ruined by warping and cracks. It is therefore essential that the timber is dried at a uniform rate. To make the timber usable for making furniture or in construction, the moisture content must be reduced to a specified percentage, otherwise the wood will continue to shrink and warp and twist as it dries out. Once the wood is sufficiently dry, it is easier to work and is stable.

The traditional method for drying or season­ing the wood is to cut the log into planks and to slack these with sticks placed between each plank to allow the air to circulate. This method will reduce the moisture content to about 15% which makes the wood suitable for working, but
this process can take2 to 3 years for hardwoods.

Most wood today is dried in temperature-­controlled kilns rather like large ovens which quickly reduce the moisture content of the wood to the suitable level. Once the wood is dried it is t tit into standard sizes and lengths.

The timber at the local do-it-yourself shop has usually been dried. As long as it is stored in a reasonably dry atmosphere it will remain fairly dry and stable, without warping or cracking. If it is stored in the open, however, it is likely to have picked tip considerable moisture and may well warp and twist when brought into a dry room.

Faults and defects :

As with any growing thing, wood is subject to faults and defects, some of which affect the strength and usefulness of the wood and others which are blemishes affect its appearance only. Sometimes it is these very faults that make the wood more attractive and more valuable: the much priced bird's eye maple with its ttiny circular patterns is a defect caused by an insect boring into the wood.

Defects are one factor in determining the quality and grade of timber. Wood that is almost free of flaws is sold for cabinet work and wood with knots and imperfections is generally sold for less-finished or construction work.

The most common flaw is a knot, the cross section of a branch exposed in sawing at the point where it starts growing from the trunk. The knot may still be fresh and tit tightly into the surrounding wood. This type of knot is not a problem and can even bean attractive feature of the wood: knotty pine is used as a decorative wall covering. Some old knots, however, tend to shrink and fall out, leaving an unsightly hole in the wood.

Certain imperfections occur after the tree has been felled as a result of uneven or too rapid shrinkage of the wood as it loses moisture. These include cracks along the length of the grain (called checks), splits or separations of fibres along the grain (shakes) and warping and bowing of hoards.

Wood has many other faults and it is also attacked by fungi and insects, and these are treated more fully in specialists hooks, which are usually available at local libraries.

Some of the snore commons faults to look for in timber warping (top) which results from uneven drying and which bows the bard across the width; knots (middle) which occur where branches join the main stock of the, tree; and splits (bottom). milled checks or shake` depending on their location, and often caused by uneven seasoning.

Hardwoods and softwoods

Hardwood and softwood are fairly arbitrary, botanical terns: no real measure of hardness divides the two types of wood and some hardwoods arc as soft or even softer than softwoods. Douglas fir is a hard softwood and bass-wood a soft hardwood. Surprisingly, balsa wood, which is the softest known wood, is a hardwood. Generally, hardwoods are more durable and more difficult to cut than soft­woods.

Hardwoods are produced by broad-leaved deciduous trees which are slower growing than softwoods, and the wood is usually denser and harder. Hardwoods are more expensive as they take longer to grow, and they are therefore reserved for fine work or are made into veneers.

Hardwoods are available in a wide array of colours and markings, from plain solid colours
like mahogany to exotically marked woods like zebrawood. Different hardwoods have specific characteristics which suit them for

special jobs: ash is flexible and extremely strong and is therefore used for implements which take a to of wear and shock, such as hammer handles.

Hardwoods which are commonly available through timber merchants include mahogany which is reddish brown and used for fine furniture, beech which is a light wood delicately marked with darker flecks, oak which is light brown and extremely tough, and teak, a warm, dark brown wood which is quite oily and is therefore used for outdoor furniture, draining boards, and for fine furniture. Larger timber yards stock more unusual hardwoods.

Softwoods are produced by trees with needle-point leaves. The most commonly used types are Red Baltic pine, Douglas fir, Parana pine, and spruce.

Softwoods

• DOUGLAS FIR: reddish brown wood with a pronounced wavy grain pattern. Almost free of knots and easy to work. Used for panelling, construction work, and furniture.
• HEMLOCK: Pale yellow with a straight grain and moderately fine texture. Used for general-purpose indoor work.
• RED BALTIC PINE: Light reddish brown wood with even texture and uniform grain. Fairly resinous wood. General carpentry and joinerv work.
• PARANA PINE: Brazilian softwood. Pleasant light to dark brown colour with red streaks. Used for indoor furniture. Easy to work but tends to split when nailed. Virtually knot-free
  with straight grain. Available in widths up to 300mm.
• WESTERN RED CEDAR: Light brown wood which is resistant to weathering and woodbor­ing insects due to a natural oil in the wood. Will not twist or warp even in heat, but bruises easily.

Hardwoods

• AFRORMOSIA: Brownish yellow wood used as substitute for teak. Oily and quite difficult to work.
• ASH: European and North American: Pale yellow wood with fairly straight grain. Tough, and bends without splitting. Used for bentwood furniture, for framing work and for tool handles.
• BEECH: Fine textured European wood, pink to yellow brown with straight grain. Easy to work and takes nails and tacks easily, so it is used for frames of upholstered furniture and cabinets.
• ELM: Distinctively grained wood with light brown colour. Strong and durable, but warps.
• IROKO: West African, similar in appearance to teak. Darkens on exposure to light. Used for joinerv work and furniture.
• MAHOGANY: Reddish wood with attractive grain pattern. A fine cabinet-making wood. African varieties darker and less expensive than those from Central America.
• MAPLE: Golden coloured North American wood. Nicely patterned, sometimes with bird's y eye. Traditionally used for butcher's blocks, as it has no odour.
• OAK: The two main varieties of oak, European or American, are very strong and dense and rather hard to work. Japanese oak is sometimes offered. It is fine grained, very stable and more expensive than European or American. Oak is used for furniture, window frames, fence posts.
  
• RAMIN: Straight-grained timber of uniform light colour used for picture-framing and mouldings.
• ROSEWOOD: Rich reddish-brown wood with beautiful grain pattern mostly used as a veneer.
• TEAK: Clear gold to dark brown colour. Hard to work and very oily, so difficult to glue and finish. Weathers to grey colour outdoors if not treated with special oil.
• UTILE: Similar to mahogany but less expen­sive. Easy to work and resists decay. Popular hardwood for furniture.
• WALNUT: Golden dark brown colour with attractive curling pattern, excellent to work and takes good finish.

Veneers

Because hardwoods are so expensive and quite difficult to work, they are often sold as veneers. The wood is shaved into very thin sheets about 1mm thick and then tut into suitably sized pieces or large sheets which are then glued on to less expensive woods or man-made sheet materials. The advantages of veneers in addition to lower cost is that, glued to a stable surface, the veneer will not twist or warp. Many timber yards sell ready-veneered plywood, blockboard and chipboard with matching iron-on edging. The most common veneer faces are oak, teak, and mahogany.

Man-made sheet materials

There are several types of sheet material manufactured either by gluing layers of veneer together or by bonding wood chips and sawdust into hoards. These sheets can he made in large sizes in a variety of useful thicknesses and, it stacked properly, they do not shrink or warp or crack. The common types arc plywood, blockboard, chipboard and hardboard.

Plywood

Plywood is an extremely versatile and strung sheet material, used for furniture work as well as for construction. It is made from layers of special veneers which are glued together. F.ach successive layer is placed at right angles to the one before to avoid any weakness resulting from grain direction. Unlike ordinary timber, plywood is strong in both directions and resist, warping or twisting. The layers are glues together in machines under pressure and heat For exterior plywood a waterproof glue is used

1 The cutaway section of a plywood sheet shows how successive layers, or plies, are glued at right angles.

The sheets are then trimmed to standard sizes. The most common sheet size sold is 1220 x 2440mm, but plywood can be bought in smaller quantities by the square metre from local shops. It is available in a variety of thicknesses from 4mm to 25mm. The more plies it has the stronger it is.

The most common types of plywood are birch plywood from Finland, the strongest and most expensive; Gaboon plywood from West Africa, the least expensive; and Douglas Fir from North America, which is medium priced. Plywood is used to make tables, wall units or cupboards. It can be stained, painted, or varnished to bring out the natural wood grain,

Blockboard

2 Blackboard is constructed with a solid core of narrow wooden strips sandwiched between layers of veneer.

Blockboard is a sheet material with a solid core made of narrow strips, usually softwood, glued together side by side and sandwiched between layers of veneer. The strips run parallel with the long side of the hoard. It is sold with a variety of hardwood veneer faces such as birch, mahogany, teak and oak.

Chipboard

Chipboard is manufactured from wood particles from both hardwoods and softwoods. Synthetic adhesives are added to the chips which are then heated and pressed into sheets. Chipboard can be waterproofed with waterproof adhesives, and, as it has no grain, it is a stable sheet, but it is not as strong as plywood or blockboard, Chipboard is available in the standard 1220-2440mm sheet size or by the square metre in thicknesses from 9mm to 25mm. It is available in different grades depending on the fineness of the chips used to make it. The smaller the particles the better the grade.

3 Chipboard is made from wood particles and special adhesives pressed together to form sheets. 4 Veneered chipboard looks like solid boards of timber and is inexpensive to buy; the sides are covered with a matching iron-on edging.

Chipboard is often veneered for use in cabinet work. Most timber merchants sell veneered boards in handy widths with matching edging. Chipboard used without veneer can be sealed with a coat of polvurethane or emulsion paint and then gloss painted, the edges smoothed by rubbing with wood tiller or plaster and then sanded down. Chipboard can also he stained with wood tones or with coloured polyurethanes. The stains look very attractive on the flecked pattern of the chipboard.

Hardboard

5 Hardboard is available plain, or perforated as sh mon.

Hardboard is one of the most useful of the sheet materials for cheap panel work but it is too weak to use on its own. It is a dark brown colour, with one face glass-smooth and the other textured with a criss-cross pattern. Hardboard sheets are manufactured from wood fibres bonded together under pressure and heat without any glue, and is very hard. It is usually available in 1220 x 2440mm sheets in thicknesses of 4 and 6.5mm. It is often used for drawer bottoms, cabinet backs and also nailed to floors as a base for laying tiles and carpets. It is also sold perforated or pierced with uniform decorative patterns for use as a storage pegboard or for wall vanelline.

6, 7 tongue-aid-groove boards are ready-proee" ed for immediate use.

Special sections

Mouldings

Most of the wood you buy will be simple rectangular pieces and sheet material, but specially shaped sections of wood are produced for specific jobs. These sections (mouldings) are used as decorative features for picture frames, skirting boards, cornicework, picture rails, or for a specific function in a piece of furniture such as carrying a sliding door. There is a wide variety of mouldings, ranging from a simple half round to a complex ogee pattern and usually one to suit each job.

Picture frame mouldings, usually milled from an inexpensive hardwood such as Ramin. are available in a wide variety of patterns. They are as marked: (a) cushion moulding, (b) spool moulding, (c) enamelled mouldmg. (d) hockey stick moulding (e) flat picture frame, (f) on temporary box moulding.

Floorings and claddings

There are two special cross sections for use as floorboards and wall cladding. Floorboards are softwood planks tongued on one edge and grooved on the other which fit together to make the floor stronger and draught-proof. Wall cladding is a finer grade of timber and is also tongued and grooved with the front face planed smooth. This type of cladding is also used for the backs of pieces of furniture such as Welsh dressers. Cladding is usually sold in packages of 20 x 2.4m lengths.

Dowels and rounds

Dowels are round wooden sticks, usually of hardwood, in diameters which range from 5mm to approximately 50mm. They are sold by the metre, usually in lengths up to 2m. Dowels are widely used in furniture, especially chairs, and are particularly easy to attach.

Rough-sawn or planed?

Softwood like pine is sold either rough-sawn or smooth-planed. Buy softwood that is already planed for anything other than construction work; although it costs more, it saves planing time and also enables you to inspect properly the boards.

Timber is sold according to the nominal dimensions. Some wood (about 3mm) is shaved off in the planing process. A 100 x 50mm hoard, for example, would have an actual size of 97 x 47mm after planing. Planed softwood is referred to as P.A.R., "planed all round". It is important to keep this in mind when planning the dimensions of your project. If you need the timber to be finished to an exact thickness, it may he better to buy the boards in the next thickness and plane them yourself to the desired MM.

Cutting to size

timber is sold in standard sections in thicknesses generally from 16mm to 30mm, in widths from 16 to about 300mm, and in lengths to about 6-7m. Shorter lengths are sold by the metre by local timber merchants. Sheet materials are sold in a standard 1220 x 2440mm size or as half or quarter sheets. Some timber merchants are prepared to cut up sheet material for you which makes it easier to transport and eliminates the need for a domestic saw. Bring a detailed cutting list of the pieces you will need with you and a try square to check that the pieces are cut at right angles.

Many timber merchants will deliver a reasonably large order at no extra charge, and some provide regular customers with discounts. Smaller merchants do not usually have facilities for delivery, but they are very helpful in cutting up pieces or in supplying oftcuts which are easier to carry hone.

Wood is expensive so plan carefully to reduce waste. If you need, say, four 1 metre long pieces, it is better to buy one 4.2m length than two 2.2m lengths. Larger timber merchants will usually not cut off short lengths but their prices are lower than those at most local shops. Find out which lengths are available before assessing the cutting cost.

Softwood is sometimes sold in two grades: joinery and construction. If the wood is not going to show, such as at the hack of cupboards, use the cheaper construction grade.

Other sources of timber

Old furniture, such as wardrobes, which can often he bought cheaply at sales, are a useful source of dry, planed hardwoods like oak and mahogany. A heavy coat of varnish may hide some beautiful boards. Remove the varnish by sanding or planing and the wood can he used for other projects. Check carefully that all nails and screws are removed as these can damage your tools such as saws and chisel.

Buying timber

The wood or sheet material selected for a job will greatly affect the amount of work and its final appearance. As the wood is the most expensive item in a project, it is important to choose it carefully and to buy good quality material.

How to choose

First decide on the type of material most suited to the article being made. Fine furniture calls for a hardwood, but a softwood such as pine is excellent for most work. Pine is easier to work as it can be bought already planed, though a few light strokes with a smoothing plane may be needed before finishing. It is much softer than hardwood, and is less expensive. Sheet materials like plywood and chipboard are ideal for making fitted units and work surfaces, where a large and stable surface is essential.

The type of wood will depend on how much money is available; chipboard is less expensive than plywood, and some hardwoods cost considerably less than others. If the wood is to be left natural, your choice will also depend on the colour of wood best suited for the article, and the grain pattern you find most pleasing.

As the wood is expensive, it is important to plan out the job carefully and prepare a drawing or diagram of the finished piece to find out how much material is needed. With hardwoods, as with knitting yarns, the colour of the wood will vary from one tree to another, so it is important to buy all the necessary wood at the same time. Planning the work out will save you the inconvenience of having to buy extra wood or the unnecessary expense of buying too much.

The wood should be well seasoned and dry. Unseasoned wood will warp, shrink, crack and how and spoil your project. Most smaller timber merchants will allow you to look at each piece before buying it. Inspect each board carefully to ensure that it is straight and true, by sighting along the length. Check for defects and imperfections like cracks, splits and loose knots. Buy wood that is relatively free of knots unless knots are to he used as a decorative feature. It is more difficult to inspect hardwoods, as they are usually sold unplaned and much of the grain cannot be seen on the rough surface of the wood.

Never buy wood that has been stored in the open as it is likely to he very wet and will warp. When buying sheet material, check the edges and ends for damage and if they are veneered, check that the veneer is properly stuck down all over the sheet and at the edges, and that the overall pattern of the sheet is pleasing. Boards which have not been stored properly, if warped, should be rejected.