WOOD

Design and Manufacture

Wood

Useful, natural material Hard and fibrous in nature 3 classifications to wood:

Hardwoods (slow growing 100 years from warmer climates)

Softwoods (quick growing 30 years) Manufactured boards (man made composites)

Each species of tree provides different timber that varies in colour, grain pattern, texture, strength, weight, stability, durability, cost and ease of working.

Hard woods

Hardwoods - broadleaf, deciduous trees shed their leaves in winter or evergreen trees that keep their leaves throughout the year.

Delicate with a shorter life span. Wood - stronger and in demand,

more expensive

Hard woodsName Origin/colour properties uses

Beech Europe/whitish pine to pale brown

Strong, straight grained, even texture

Furniture, turnery

Elm Europe/light, reddish brown

Tough, durable, difficult to work, cross-grained

Turnery, furniture, outdoor use

Oak Europe: light brownJapan: pinky-brown

Strong, durable, hard, tough, tannic acid that corrodes steel leaving blue stains

Furniture, flooring, boat building, veneers

Ash Europe: pale cream and light brown

Straight grained, coarse texture, good elasticity, works and finishes well

Sports equipment, tool handles, cabinet making, laminating

Mahogany

Central+South America, W.Indies, W.Africa/ pink reddish brown to deep brown

Fairly strong, medium weight, easy to work, durable, prone to warp

Furniture, panelling, veneers

Teak Burma, India/Golden Brown

Hard, strong, durable, natural oil – water resistant, works well but blunts too quickly

interior/exterior furniture, boat building

Walnut Europe, USA/ yellow, brown, bronze, dark lines

Attractive grain, cross grain makes finishing difficult

Veneers, furniture,

Soft woods

Softwoods - conifer trees that are cone bearing.

They have leaves all year round, known as evergreen,

Strong and withstand most weather conditions.

Cheaper to buy and readily available most of year.

softwoods

Name Origin/colour Properties/characteristics

uses

Scots pine Northern Europe, Russia/ Cream, pale brown

Straight grained but knotty, fairly strong, easy to work

Furniture, joinery, construction work

Red Cedar Canada, USA/dark, reddish colour

Light, soft, weak natural oils make it weather durable

Exterior shingles, cladding, sheds

Parana Pine South America/ pale yellow with red/brown streaks

Hard, straight, know-free, strong and durable, smooth finish, tends to warp, expensive

Quality interior joinery: staircases, built in furniture

Spruce (whitewood)

Northern Europe, America/creamy white

Fairly strong, small hard knots, resistant to splitting, resin pockets, not durable

Construction, general indoor work

Manufactured Boards

Strong, stable and economical Suited to mass produced furniture. Boards available in large sheets Beneficial to the environment – use up waste

products from the sawmill that are made into particles

Advantages: cheap, stable, thin veneers of expensive timers can be used to decorate, boards available in large sheets.

Disadvantages: edges require ‘facings’, repair and maintence can be difficult.

Manufactured BoardsName Composition Properties/

working characteristics

Uses

Plywood Thin veneers, cross laminated using odd number of layers

Stable, strong and easy to machine

Furniture, joinery, construction work

Block board 25mm strips glued together and faced with ply

Stiff, heavy, good load-bearing

Furniture, worktops, veneer groundwork

Hard board Highly compresses wood fibres

Cardboard like, weak and brittle

Low cost furniture parts – cabinet backs, drawer bottoms

MDF(Medium Density Fibreboard)

Compressed wood fibres

Easily machined, moulded and painted

General shell/painted work, veneer ground

Chipboard Compressed wood chips

Stiffness and strength vary with density(thick)

Furniture shell, good veneer ground

Joining Methods

Joints

Glue (Adhesive)

Nails

Screws

Adhesives

Used to bind two pieces of material together Selection of which adhesive depends on

purpose of product and material to be joined. Wood glue join timber products Some will allow for repositioning and

adjustment Others can bond straight away. Adhesives will not usually bond to greasy or

wet surfaces

Types of adhesives for woods PVA glue(polyvinyl acetate)

Mostly used wood glue. Sold ready mixed Strong and doesn’t stain Excess wipes off with damp cloth Light cramping required Seal edges of MDF before painting

Epoxy Resin Two part adhesive for unlike materials Bond glass, ceramics, wood, metal and

thermosetting plastics Mixing resin triggers chemical reaction that sets

adhesive Waterproof, good gap filler and electrical insulator Restricted to small scale applications as cost are

high Not suited to thermoplastics

Types of screws

COUNTERSUNK - SLOT HEAD: This can be used for general woodworking for example fitting hinges to doors. Because the screw is countersunk it can be tightened 'flush' to the surface of the material.

POZIDRIV HEAD: Used with special screw drivers which will not slip when pressure is applied. This is ideal when using screws in corners or confined spaces.

ROUND HEAD SCREW: These are used for fixing pieces of material together where countersunk holes are not being used. Round head screws can look quite decorative especially if they are made of brass.

Types of screws (contd)

RAISED HEAD SCREW: Used to fit door handle plates and decorative features that must look good.

CHIPBOARD SCREWS: The thread on this type of screw extends all the way along the length. It is best used with chipboard

SELF-TAPPING SCREWS: these are normally used to cut a thread in metal. A hole is drilled in the metal, a fraction smaller than the width of the screw. The self-tapping screw is then turned into the hole cutting a thread.

Types of nails ROUND WIRE NAIL - This is used for general work. It is not attractive

in shape and it can split wood when hammered in position     

OVAL WIRE NAIL - This is a long nail and care must be taken when it is hammered into the wood. It is unlikely to split the wood.     

LOST HEAD NAIL - This is ideal if it is necessary to hide the head of the nail as a punch can be used to hammer the head beneath the surface level.     

PANEL PIN - A very popular way of joining woods although glue is usually included as part of the join.     

TACK - Can be used for fixing textile materials to wood for example, fixing upholstery to furniture.     

   

HARDBOARD PIN - The diamond shaped head is hidden when used in materials like hardboard    

Joints

Bridle Joint

Halving joint

Dove tail

Cross having

Mortise and Tenon

Finger

Knock down fitting

Can be put together easily, normally using only a screw driver, a drill, a mallet/hammer and other basic tools.

Temporary joints - many used to permanently join together items such as cabinets and other pieces of furniture that are purchased in a flat pack.

Knock down fittings PLASTIC CORNER BLOCK (FIXIT BLOCKS):

The corner block is pressed against the two pieces of material (normally wood based). Screws are used to fix the block into position. This type of joint is used to fit modern cabinets such as those found in a kitchen. It is a relatively strong joint although it has the advantage that it can be dismantled using a screwdriver.

NATURAL WOOD FITTING (SQUARE SECTION BATTEN): A piece of material such as pine can be drilled and

screws can be passed through these holes. This gives a cheap and effective knock-down joint. The screws are normally countersunk into the knock-down fitting.

RIGID JOINT: These are normally molded in plastic which makes

them strong. Screws pass through the four holes which hold the sides at each corner firmly together.

Knock down fittings TWO BLOCK FITTING (LOK-JOINTS):

These are made from plastic. A bolt passes through the first fitting into the thread of the second. As the bolt is tightened it draws the two fittings together. The pins help keep the fitting straight. This gives a very strong joint and it can be dismantled using a screwdriver.

CAM LOCKS: The disk fits into a recess in the first side of the

cabinet. It rotates by inserting a screwdriver into the slot in its side. The shaft is screwed into the second side of the cabinet. The collar of the shaft is passed through the hole in the second slot in the disk. When the disk rotates the shaft is locked in position. This keeps both sides of the cabinet locked together.

SCAN FITTINGS These are strong enough to be either permanent or

temporary joints. The cylinder is inserted into the first side of a cabinet in a pre-drilled hole. The screw is then pushed through the hole in the second side until it meets the cylinder. It can then be tightened with a screw driver until both sides of the cabinet pull together.