DT

Hardwood

Hardwood

Wood that comes from broad-leaved trees that lose their leaves in autumn

Hardwoods

Oak, Mahogany, Beech, Maple

Softwood

Wood that comes from fast-growing evergreen trees with cones and needles

Softwoods

Pine, Redwood, Yellow Cedar, Fir

Oak

Light brown colour, strong and tough, corrodes steel screw and fittings and reacts with certain adhesives

Uses of Oak

High quality of furniture and interior woodwork

Mahogany

Rich reddish-brown colour, strong and durable, interlocking grain

Uses of Mahogany

Good quality furniture, musical instruments

Beech

White in colour, close-grained, hard and strong, prone to warping

Uses of Beech

Furniture, Toys, Tool handles

Maple

Durable, strong, long-lasting, polishes well

Uses of Maple

High-end furniture, Flooring, cabinetry

Pine

Durable and easy to work with, resistance against decay

Uses of Pine

Flooring, windows, furniture

Redwood

Relatively strong, knotty, durable when treated with a suitable coating or treatment, low cost

Uses of Redwood

General woodwork, cupboards, shelves, roofs

Yellow Cedar

Very pale in colour, light in weight yet rigid

Uses of Yellow Cedar

Furniture, Boat building and veneers

Fir

Excellent strength, resistance to splitting, bonds well with adhesives, rot resistant

Uses of Fir

Boats, flooring, doors

Manufactured board

A range of sheet materials produced by pressing and bonding together wood particles, fibres or veneers to achieve particular characteristics

Manufactured boards

Chipboard, Hardboard, Medium Density Fibreboard (MDF), Plywood

Chipboard

Made up of small chips of wood bonded together with resin and compressed to form sheets. It is often used in furniture for use indoors, and it is covered in a plastic coating or veneer for a more aesthetically appealing timber.

Hardboard

Madre from pulped wood fibres that are pressurised until the fibres bond together to produce a board that is smooth on one side and rough on the other. It is not as strong as the other boards and it is typically used in non-structural situations, such as the back of cupboards.

Medium Density Fibreboard (MDF)

Made up from very fine wood dust and resin pressed into a board. This material can be worked, shaped and machined easily and has considerably more strength than hardboard due to the use of resin as a bonding agent. It is used in many applications, indoors, and it can be easily finished with veneers or paint.

Plywood

Made from very veneers of timber with the grain of each layer being at right angles to the layers either side of it. The layers are bonded together by resin and pressure. A number of different types of plywood are available, and these are often referred to a grades.

Types of plywood

Boil resistant plywood, Flexible (flexi) plywood, Interior plywood, Laser plywood, Marine plywood, Weather and boil proof plywood

Benefits of working with manufactured boards

They are available in a range of sizes and thicknesses, boards are designed for specific purposes, they are environmentally sympathetic, they do not split like natural timbers do, they are available in ready finished formats

Shaping and joining timber methods

Steam bending, Laminating

Steam bending

Steam is introduced into a steam chamber heating the veneer. After some time the veneers are removed and are malleable and flexible, meaning that they can be bent into different shapes. They are positioned around a former and clamped, and left to cool. Once cooled they will retain this new shape.

Laminating

This involves using a number of thin laminates of timber and bonding them together over a former. Adhesives used in this process cure and set the layers of laminate while they are held in place. PVA is commonly used to bond timber as it is relatively cheap, non-toxic, and easy to work with. After application, the PVA will dry to be transparent.

Thermoforming

Plastic materials that can be repeatedly softened by heat and formed into shapes which become hard when cooled

Thermosetting

Plastic materials that can be softened and formed into shapes which become hard when cooled and cannot be softened again

Elastic state

The state in which a thermoforming polymer is at a temperature that produces a stretchy consistency and in which it can be shapes, but will not retain its form without being held in place. This state is used for instance in line bending, vacuum forming or dome blowing.

Plastic state

The state in which a thermoforming polymer is at a temperature that produces a consistency that is softer and more malleable than the elastic state. This state for instance is used in injection moulding.

Seasoning

The process of drying out timber so that it becomes strong and will not change its shape over time.

The process of seasoning

A kiln is used, and allows air to be warmed and circulated by fans to speed up the seasoning process. As the warm air circulates around the inside of the kiln, it dries the timber placed inside it.

Benefits of kiln drying timber

It is easier to monitor the timber, and it is a much quicker process than naturally seasoning timber

Drawbacks of kiln drying timber

It is more expensive than natural seasoning, and a kiln has a maximum capacity due to its physical size, which limits how much timber can be seasoned at one time. Sometimes timber can warp in the process.

Warping

The distortion or twisting that can occur to timber, often as a result of poor storage, poor seasoning or natural defect

Composite

A term used to describe a material that is made by combining two or more materials.

Why are composites used?

They can be engineered to meet the exact requirements of a specific application. By combining individual materials, each becomes enhanced and typically the advantages of the new material means it is more efficient, stronger and lighter.

Composites examples

Concrete, small stones and gravel with cement and sand

Properties of metals

Brittleness, Ductility, Hardness, Elasticity, Malleability, Toughness, Work hardening

Brittleness

Something that has no flexibility: when it breaks, it shatters into multiple pieces

Ductility

The ability to be stretched, bent, deformed and shaped without breaking

Hardness

Resistance to scratching, cutting and wear

Elasticity

The ability to return to its original shape after it has been deformed

Malleability

Something that can be easily shaped, spread, flattened, hammered and deformed

Toughness

Resistance to breaking, bending or deforming

Work hardening

When a non-ferrous metal is continually bent, hit or shaped over a period of time

Annealing

When a metal is annealed, it is heated to a specific temperature and then cooled, which changes the molecular structure of the material, resulting in the metal being softened. This means that a metal has been annealed and can be cut and shaped more easily than if it had not been.

Ferrous metals

Metals and alloys that contain iron. They all have some properties which relate to iron: they conduct heat and electricity, and they react with oxygen and corrode (rust) unless they are treated to prevent this. They also have high melting points.

Ferrous metals:

Cast Iron, Stainless steel, Mild steel, High Carbon steel

Cast iron

Brittle, corrodes by rusting

Uses of cast iron

Casting and base metal for all steel alloys, manhole covers, car brake discs

Stainless steel

Hard, corrosion and wear resistant to a large extent.

Uses of stainless steel

Cutlery, kitchen equipment, sanitary equipment, surgical equipment

Mild steel

Tough, ductile, malleable, good tensile strength, poor resistance to corrosion

Uses of mild steel

General purpose engineering and construction material, nuts, bolts, car body panels

High Carbon steel

Hard and tough but the increase in carbon makes it more brittle. It can be heat treated to further enhance its properties.

Uses of high carbon steel

Cutting tools, ball bearings, hand tools; screwdrivers, hammers, chisels and saws

Non-ferrous metals

Metals and metal alloys that do not contain iron

Non-ferrous metals:

Lead, Aluminium, Brass, Copper

Lead

Is very soft and malleable. It has one of the lowest melting points of a metal that is solid at room temperature

Uses of lead

Roofing, construction, casting, lead acid batteries

Aluminium

Light in colour although it can be polished to a mirror-like appearance. It is very light in weight and the most abundant metal in the Earth’s surface.

Uses of aluminium

Saucepans, cooking foil, takeaway containers, window frames, ladders, bicycles

Brass

It is golden yellow in colour and is often machined from cast ingots and billets of raw material.

Uses of brass

Used for decorative metal work such as handles, candlesticks, ornaments, pins on electrical plugs, and musical instruments

Copper

A very ductile and malleable metal. It is often red/brown in colour and it goes green when it corrodes, forming a substance called verdigris. It is an excellent conductor of heat and electricity

Uses of copper

Used for plumbing, cookware, electrical fittings and roof coverings

Cutting tools

Hacksaw, Guillotine, Tenon saw, Cross-cut saw, Panel saw

Hacksaw

Used for all metals, cuts straight lines

Guillotine

Used on sheet metal, cuts straight lines

Tenon saw

Used for wood, cuts precision tenon joints

Cross-cut saw

Used for wood, cuts across the grain, producing a straight edge

Panel saw

Suitable for heavy duty work, cutting all types of wood, and sheets of plastic, cuts straight lines

Datum

The flat face, or straight edge of the material from which all measurements should be taken

Methods of securing material

Clamps, Vices and Jigs

Tools for measuring and marking out

Marking gauge, Mitre square, Centre punch, Compasses, Mortise gauge, Combination square, Try square, Scriber

Scriber

Used for marking out a sharp, straight line

Try square

Used to mark out a perpendicular/90° angle

Mitre square

Used to mark out a 45° angle

Marking/mortise gauge

Used to mark out a parallel line

Centre punch

Used to mark out the centre of a hole, before it is drilled

Compasses

Used for drawing arches, curves and circles

Combination square

Used for measuring a 45° angle

Odd leg caliper

Used to mark out a parallel line

Precision instruments for measurement

Inside and outside calipers, Micrometre, Vernier gauge, Digital vernier caliper

Inside and outside caliper

Caliper used to measure the inside or outside of material

Micrometre

A precision device used to measure depth, length or thickness to a high degree of accuracy

Vernier gauge

A manual caliper used to measure internal and external distances with precision and accuracy

Digital vernier caliper

A precision instrument used to accurately and easily measure internal and external distances. Can measure in either imperial or metric units