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The Furnishing industry uses a wide range of materials such as timber and other wood products, adhesives, hardware items, glass, plastics and surface finishes to name just a few. In this section we will talk about: Identifying the main materials used in the furnishing industry
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The Furnishing industry uses a wide range of materials such as timber and other wood products, adhesives, hardware items, glass, plastics and surface finishes to name just a few. • In this section we will talk about: • Identifying the main materials used in the furnishing industry • Understanding the nature and characteristics of these materials.
Trees • The main construction materials used in the furnishing industry are wood products. • You will need to understand the characteristics of these materials so you can work with them successfully. • Food produced by the leaves flows downward through the live bark • Water and food flow upward through the sapwood • Leaves: absorb carbon dioxide, produce food and expel oxygen • Trees are the natural resource from which all wood products are made.
Parts of a Tree How the tree gets the food and water necessary for its growth.
Tree Structure • The roots extract mineral salts and water from the soil and the leaves produce sugars from carbon dioxide and water by the process called “photosynthesis”. • This process can only occur in the presence of sunlight and chlorophyll (green substance in leaves). • The illustration shows the parts of a tree trunk.
Structure of a Tree • Dead Bark Or outer bark protects the trunk and helps to reduce water loss from the living cells of the tree. • Live Bark Is a layer of living tissue under the dead bark which conducts food from the leaves to the other parts of the tree. • Cambium Layer Is a thin layer of cells inside the live bark which is responsible for all growth in the thickness of the tree trunk. • The cambium grows wood cells on the inside and live bark cells on the outside.
Structure of a Tree • Sapwood Is the new wood under the cambium layer. It is usually lighter in colour than heartwood and it conducts water and food materials from the root system to the other parts of the tree. • Heartwood Or truewood is made up of dead cells. It is much more durable than sapwood and is formed by blockage of the channels which conduct food materials when food stored is converted into tannins, resins and other substances the tree needs to survive.
Structure of a Tree • Pith Is the soft pulpy core at the centre of the tree. It is also called the Medulla and is usually about 1cm in diameter. • Medullary Rays Are groups of wood cells which radiate out from the pith through the heartwood and sapwood zones of the tree. Food materials are conducted horizontally in the trunk of the tree through the medullary rays. • Growth Rings Show the annual growth in the trunk of the tree. As growth slows down in the winter compared to the growing season, the layers of wood cells (late wood) are smaller and more closely packed, forming a ring which is darker in colour than wood grown at a faster rate (early wood). • The age of the tree can be determined by counting the number of growth rings.
Wood Structure • Hardwoodcontains large tube-like vessels called pores which conduct much of the water and food materials. The smaller, thick walled cells shown in the diagram are wood fibres which make up most of the wood substance. • Softwoods are made up of long thin cells or trachiedswhich are much smaller than the pores in hardwood. The walls of the trachieds make up most of the wood substance.
Timber • Logs are usually sawn into commercial sized timber soon after the tree has been felled, to minimise damage from shrinkage such as splitting at the ends of the log.
Wood Conversion • The method used to convert a log into commercial timber will depend on the type of timber and its end use. • Live sawing is the simplest method of cutting logs into boards. Parallel cuts produce wide boards, some of which can be prone to excessive warping and uneven shrinkage. Some live sawn boards could be classified as back sawn or quarter sawn.
Wood Conversion • Quarter sawing produces boards with faces roughly parallel to the medullary rays and at right angles to the growth rings. Timbers with pronounced medullary rays, such as silky oak, have a distinctive figure when quarter sawn. Quarter sawing is the least economical method because more timber is lost in waste. Boards are classed as quarter sawn when the average inclination of the growth rings to the face is greater than 45°
Wood Conversion • Back sawing produces boards with faces generally tangentialto the growth rings. This method allows for sawing around defectsin the log with little waste. • Cabinet timbers with distinctive growth rings are often back sawn to give the best figure on the face of the board. Trade practice is to class timber as back sawn when the average inclination of the growth rings to the face of the board is less than 45°.
Selection & Defects • When you select timber for a furniture project, you should inspecteach piece for defects. • A defect in timber is anything that affects its normal appearance, durability or strength. • The presence of a defect doesn't always mean that the timber can't be used in your project.
Selection & Defects • If the defect doesn't weaken the wood too much the timber could be used where the defect will not be visible in the finished article. • Knots are branches embedded in the tree and cut through in the milling process. They tend to weaken the timber and spoil the appearance of some cabinet timbers. • Knots can shrink, become loose and may even fall out.
Knots • The ordinary knot (roughly circular in shape) is formed when the cut is madeacross the embedded branch • The spike knotis formed when the cut is made in the same direction as the embedded branch.
Shakes • Shakes are caused by layers of wood separating between the growth rings or along the medullary rays. • Layers sometimes separate when uneven shrinkage occurs in the heartwood while the tree is still standing. It might be possible to cut the board down to remove the defect and salvage some of the timber.
Pipe • A pipe or cylindrical hole forms when the wood around the pith decays. • A piece of timber with a small pipe might still be used if the pipe was not visible in the finished article and did not severely weaken the timber or cause excessive warping.
Gum veins • Gum veins are cavities which contain resin substances or gum. • Gum veins can occur naturally in the wood or they can be caused by an injury to the tree. • Gum veins disfigure and sometimes weaken timber. • In some timbers, the substances found in gum veins will `bleed' through paint or clear wood finishes. • You should always consider this when selecting timber for a project.
Selection & Moisture Content • Moisture content affects the stability of timber. • If moisture content increases, timber swells. • If moisture content decreases, timber shrinks. • This is called `movement' in timber. • Timber that is used in a furniture project should be subject to minimum movement. • In other words, the timber should be properly seasoned. • Seasoning is the process of drying out most of the water from the cell walls and cell cavities of the wood.
Seasoning • Air seasoning is a natural drying method in which green sawn timber is placed in well ventilated stacks out in the open. • Air seasoning could take two or more years depending on the type and thickness of the timber. • Kiln seasoning is an artificial drying method which could take a few days or a few weeks, depending on the type and thickness of the timber. • The timber is placed in large drying rooms called kilns and stacked so that air can circulate around the boards. • Humidity and temperature are controlled in the kilns during the seasoning process.
Shrinkage • Shrinkage occurs in the seasoning process as the water dries out of the wood. Wood fibres become smaller causing dimensional change in the boards being seasoned. • Very little shrinkage occurs in the length of the board. Most shrinkage occurs in the direction of the growth rings which tend to straighten out causing `cupping' of the board.
Selected timber for furniture making should be properly seasoned and allowed to stabilise in the local atmospheric conditions. • Timber tends to reach a moisture content that is in equilibrium with the moisture content of the surrounding air over a period of time.
Equilibrium Moisture Content (EMC) • EMC is usually within the range of 10%-15% of the dry weight of the wood. • Except in very dry inland areas or tropical coastal districts. • Using timber that is properly seasoned and stabilised in the local conditions for at least a few weeks, will minimise movement (swelling and shrinking). • Movement in cabinet timbers can cause problems such as joints opening up, drawers and doors binding and solid timber panels splitting or warping.
Cabinet Timbers • Timbers could be selected for their colour and figure or their workingand finishing characteristics. • Figure is the pattern in the timber caused by variations in colour, grain and texture. • Grain refers to the general direction of the wood fibres in the board. • Texture refers to the arrangement and size of the cells in the wood structure and is described as coarse, medium or fine. • Page 146 & 147 provides a table of local and imported timbers
Nails • The illustrations below show a selection of common nail type fasteners used in the Furnishing Industry and other woodworking trades.
Nails • Bullet head nails are general purpose nails used for fastening timber framing, mouldings, flooring, general finishing and cabinet work. • For exterior applications galvanised nails should be used. • Sizes range from 25 x 1.6mm to 150 x 5.6mm.
Nails • Flat head nails are used for fastening thin material such as case timber where the nail head does not have to be punched and filled for appearance, or where the flat head might prevent the nail from pulling through. • Sizes range from 30 x 2mm to 100 x 4.5mm. Smaller sizes such as 25 x 1.4mm are often sold as wallboard nails.
Nails • Collated nails are used in a finish nailer or bradder for assembly work. • Nail lengths usually range from 32mm to 65mm. • Particleboard nails have been designed specially for fastening particleboard. • The twisted thread provides more grip in the flaky structure of particleboard than bullet head nails. • Usual sizes are 25 x 2.5mm, 40 x 2.8mm and 50 x 2.8mm.
Nails • Process nails have a glue coating which melts when the nail is driven. • They are used where the added strength of the adhesive is an advantage such as in fastening framing brackets. • A common size is 30 x 2.8mm.
Nails • Hardboard nails are used to fix high density compressed fibre boards such as masonite, to a frame. • The tapered head is designed for ease of entry into the hard surface of the sheet. • Usual sizes are 25 x 1.8mm, 25 x 1.6mm and 20 x 1.6mm.
Nails • Brads or panel pins are like small bullet head nails and are used for very fine nailing, particularly of thin material such as plywood. • Usual sizes are 12 x 1mm, 15 x 1mm, 20 x 1.2mm and 25 x 1.25mm.
Nails • Upholstery nails are used for visible fastening of fabrics to the wooden frames of covered furniture; • They are available in a range of colours • The usual length is 20mm. • V -Nails are used to fasten the mitred corners of picture frames • They are punched into the back of a frame across the mitre by a special hand operated tool or a pneumatic machine. • Sizes range from 7mm to 15mm.
Nails • Escutcheon pins are used to fasten escutcheon plates (keyhole covers) to cabinet doors and drawers. • Usual length is 15mm; • available in brass as well as other matching finishes for available escutcheon plates. • Veneer pins are like very fine brads, sometimes without heads. • They are used to hold pieces of wood veneer in place while inlaying decorative patterns.
Nails • Broad crown staples are used by upholsterers for fastening fabrics to the wooden frames of covered furniture. • Staples can be applied with either a manual staple gun or a pneumatic tacker. • A typical size could be 14mm crown and 9mm legs. • Narrow crown staples are often used in assembly of light frames and furniture components as an alternative to nailing and are applied with an air tacker. • The crown is usually 6mm and length ranges from 13mm to 32mm.
Nailing Methods • The illustration on the right show basic nailing where the thinner timber is always fixed to the thicker piece. As a general rule, the nail should penetrate the thicker piece roughly twice the thickness of the piece being fastened. • A longer nail should be selected if nailing into end grain. If a shorter nail is necessary, or more holding power is required, a threaded nail should be used.
Nailing Methods • Dovetail nailing, illustrated below, provides greater joint strength than nails which are parallel to the edges of the timber. Because the nails are angled toward each other, they are more difficult to withdraw.
Nailing Methods • Skew nailing is used where timber thickness or position prevents other methods from being used. The illustration shows how the nails are skewed to the face of the timber. • A nail punch is used to drive the nail after it has been started so the hammer doesn't mark the face of the timber. Skew nailing is most successful and easiest to accomplish when the joint is clamped firmly together.
Screws • Head Types • The choice of head type will usually depend on the application for which the screw is to be used. For example, a countersunk head would be chosen where the of the material to be fastened. screw head is required to be flush with the surface
Types of Screws • Countersunk screws are used where a flush finish is required. A countersinking bit is usually used to form the tapered hole (countersink) that the head fits into. • Raised head screws are often used for decorative purposes such as fittings and handles and for fixing sheets with a cup washer. • Round bead screws are sometimes used where the material being fixed is too thin to be countersunk.
Pan head screws are commonly used for sheetmetal work. They are usually self tapping screws. • Bugle head screws are generally used for fixing plasterboard to wall studs. • Wafer bead screws have a lower profile than round, raised or pan head screws and are used where a less obtrusive finish is required.
Types of Screws • Slot Types • The type of slot in the screw head will determine the type of driver to be used. • It very important that a correctly fitting driver tip is used to prevent slipping which can damage both the screw head and the tip of the driver.
Slotted Head Screws • Slotted screw heads are the traditional type used on conventional wood screws. • The tip of the driver you select for the job should be the thickest that fits all the way into the slot. • The width of the driver should roughly equal the diameter of the screw head for maximum purchase or turning power.
Phillips Head Screws • Phillips head screws with their cross shaped slot are probably the most common type of screw used today. • The driver tip selected should fit snugly into the slot without rotational movement or play. • Square slots are usually found in screws which are manufactured for special purposes such as in knock-down furniture. • Square slots provide a very positive drive and minimise slipping.
Hexagonal Slots • Hexagonal slots are often used in special purpose screws such as for knock-down furniture, for example large screws that require an allen key as the driver.
Thread Types • Conventional wood screws are used for fixing to timber. A clearance hole for the shank is drilled to prevent binding. • Longthread screws are fully threaded to give extra holding power. • When using long thread screws clamp the joint or drill a clearance hole, otherwise the screw will push the joint apart as the tip begins to penetrate the base piece.
Selecting Screw Length • Generally, the length of the screw should be 2 to 2.5 times the thickness of the material being fastened. • For materials over 30mm thick, screw penetration of 30mm into the base material is usually sufficient.
Drilling Screw Holes • Conventional wood screws require two different sized holes to be drilled to allow full pressure to be applied to the screw and also for ease of turning the screw in the material. The illustration below shows the parts of a wood screw and the holes required. • A clearance hole, slightly largerthan the shank of the screw is drilled through thematerial being fastened to prevent binding. • A pilot hole the size of the screw's core is drilled in the base material allowing the screw to cut its own thread. A special bit is used to cut the countersink so the screw head will finish flush with the surface of the material.
Cover Caps • Plastic cover caps are often used to hide screw heads in cabinet carcase construction. They are available in a range of colours to suit wood veneer and other finishes on manufactured boards. Push on cover caps have a projection which locks into the cross slot of the screw or connector. The screw head must be flush with the surface of the material. Snap on cover caps are designed to be used with countersunk head screws.
Knock Down Fittings • Knock-down fittings allow items of furniture to be assembled and disassembled any number of times. The assembly drawing below shows a cabinet that is constructed from a manufactured board and assembled using a variety of knock-down fittings. • Modifications such as changing the position of the shelf or adding some extra shelves are made simple. • Also transport and storage are simpler and cheaper when the unit is disassembled or knocked down. • Some of these fittings are made for one purpose only. Others are versatile and may have several different applications.
