GCSE REVISION NOTES. Metals are can be classified into two types of materials:-

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1 GCSE REVISION NOTES METALS Metals are can be classified into two types of materials:- a. Ferrous Metals b. Non-Ferrous Metals. Ferrous metals will corrode (rust) therefore need to be protected by applying paint, grease, oil, galvanizing, zinc plating to its surface. Non-Ferrous metals do not corrode (rust) as easily as ferrous metals and are usually more expensive. Most non-ferrous metals are usually mixed with other metals to make ALLOYS. : In In the the table drawn below categorize the the following metals into into ferrous and non-ferrous and non-ferrous metals: metals: Aluminium Copper Aluminium Iron Steel Copper Iron Brass Cast Steel Iron Brass Tin Lead Cast iron Tin Stainless Steel Tool Steel lead Stainless Steel Tool steel Ferrous Metals Non-Ferrous Metals

2 Metals can be joined together in the following ways:- Welding: The joining together of two metals can be achieved by using a variety of processes such as:- Manual metal arc welding Tig welding (Tungsten inert gas) Friction welding Gas welding Mags welding (Metal active gas) Soldering Nuts and Bolts: Nuts and bolts produce what can be described as a removable joint where as a welded joint is permanent. They come in various sizes and lengths and can be manufactured from high tensile steel for strength. Adhesives: Adhesive are fast becoming an alternative method of joining materials and care should be taken when used for joining metals. Draw a neat sketch below to show how a typical nut and bolt joint should look like. Label your sketch. List two advantages a welded joint has over a bolted joint

3 Casting: Casting requires the pouring of molten metal into a pre-defined shape or mould usually made in sand, but also can be into a steel mould. Sand casting produces a rough surface finish. Casting into a steel mould (Die Casting) can produce a cast that requires virtually no further finishing to the surface. : Make a list of tools and machines in the workroom that have been made from cast WOOD There are two main categories of wood types:- a. Hardwoods c. Softwoods Hardwood comes from trees that loose their leaves in winter for example English woods such as Oak, Ash, Beech, Chestnut, Apple, Elm and Lime. Tropical hardwoods come from trees that have broad leaves for example Mahogany, Iroko, Sapele and Teak. Also Balsa Wood (this is sometimes used as a trick question). Hardwoods are usually difficult to cut and shape but can be used to produce an excellent surface finish.

4 Softwood comes from evergreens for example Scots Pine, Baltic Pine, Red Deal and Pirana Pine. Open grain wood is usually easy to cut and shape. Some pines can take a good surface finish. Complete the table drawn below stating as many common uses for hardwoods and softwoods as you can. SOFTWOODS HARDWOODS Manufactured Boards:- PLYWOOD is made up from thin veneers of wood laid at right angles to one another and glued together with P.V.A. (Poly Vinyl Acetate) glue. BLOCK BOARD is made up from wooden blocks glued together and faced with a veneer of a better quality wood. CHIPBOARD is made up from wood chips mixed with glue and rolled into a board product. MDF (Medium Density Fibreboard) usually used in the construction of manufactured furniture i.e. kitchen units, bedroom furniture etc. Wood Joints:- These are used to increase the surface area of the wood thereby allowing more surface area to be applied to increase the strength of joint. Box joints such as DOVETAIL a decorative joint used a lot in the production of quality furniture. LAP JOINTS are one of the most simple box joints but are relatively weak. COMB or FINGER JOINTS have interlocking fingers, which greatly increase the surface area of the joint but they require to be made accurately or they will fail quite quickly.

5 Frame Joints:- MORTICE & TENON JOINTS have also got to be produced very accurately for strength. Most mass produced joints of this type are cut by machine, which produces a strong joint. BRIDLE joints are used extensively in the production of fences, a joint that can be strengthened by the addition of a peg driven through the joint. CROSS HALVING is a joint that allows two pieces of wood to be joined without the joint being twice the thickness of the original material. In the space below draw a neat 3D drawing of the following joints:- 1. Dovetail 2. Mortice and Tenon Make a list of the tools and equipment needed to make the joints named above. Components:- Hinges- Screws- Nails- Bolts- Used on doors and lids etc. Wood screws for fastening wood together. Various types ranging from panel pins to floor brads (special nails for fitting floorboards). Used to connect components together. Bolts are threaded partly up its shank where as a machine screw is threaded all to the top of the shank. Equipment:- Try Square- Used for checking and marking 90º. Rules- Scribers- Used for measuring. For marking lines etc on steel. Mitre Square- Used for marking and checking 45º.

6 Dividers- Chisels- Saws- Used for marking curves or circles on material. Bevel edge type use for dovetail joints, firmer chisels are for general use. Metal chisels are called COLD chisels and are much stronger. Most wood saws usually have larger teeth for cutting. Two common saws used are the tenon saw and the coping saw. Metal cutting saws have finer teeth for cutting. Two common saws used are the hacksaw and junior hacksaw. Describe with the help of a flow chart the step-by-step process of making a single draw complete with handle. (State the components to be used and the tools and equipment needed)

7 PLASTICS Plastics are man made with a structure made up from long chains of organic molecules. Plastics are usually made from crude oil and are divided into two distinct categories:- 1 Thermoplastic- By far the most common, it easily moulded into a variety of shapes by the application of heat (vacuum forming) further application of heat makes the product return to its original form. This is also known as plastic memory. (recyclable plastics) Most common forms are:- Polystyrene Acrylic (Perspex) Polythene P.V.C 2 Thermosets- This type of plastic can only be moulded once, after that further heating will destroy the product. Most Common forms are:- Bakelite (Electrical fittings) Urea Formaldehyde Polyester Resin (Used in fibre glass) List five items that could be manufactured from Thermoplastic plastic List five items that could be manufactured from Thermoset plastic

8 SYSTEMS CONTROL System control works on the principal of:- 1 INPUT 2 OUTPUT 3 CONTROL An input is provided by a sensor, this is a device that measures a certain physical property such as:- TIME PRESSURE TEMPERATURE LIGHT SOUND MOVEMENT The signal from these sensors is sent to a control device, this can be a:- LIGHT MOTOR SIREN VALVE A good example of system control is within a central heating system in a home. This is a classic example of a Closed Loop Control System. The INPUT device is the room temperature sensor (thermostat). This measures the room temperature. When the temperature reaches the pre-set limit the sensor sends a signal to the CONTROL box that makes the decision to switch off the boiler and also switch off the circulation pump. The OUTPUT is therefore the stopping of hot water being circulated or the starting up of the system.

9 In the space below can you name and describe another example of a controlled system using input, control and output devices. STRUCTURES Natural structures are for example:- Trees Human Skeleton Honeycomb Man made Structures are for example:- Bridges buildings pylons The use of the triangle shape is the basis for building light strong structures this can be seen in the construction of pylons. When a structure has forces trying to pull it apart it is said to be under TENSION. (Think what happens when an elastic band is pulled apart). When a structure has forces pushing against it. It is said to be under COMPRESSION. (Think what is happening to your chair legs when you sit on it). MOST MATERIALS PERFORM BETTER UNDER COMPRESSION.

10 Other common forces:- Bending Forces- Forces that try to bend a structure (Think of a plastic ruler supported between your hands - it easily bends) Torsion Forces- Forces that cause a structure/material to twist (Think of a drive shaft on a car). Shear Forces- A tension force applied along two pieces of metal not lying in the same plane (Think of the metal guillotine). List below the forces you think are acting upon your home right at this moment. Give an explanation on why these forces are taking place.