Basic Knowledge
- Ferrous metals- Contains iron and carbon.
- Non ferrous- Does not contain iron.
- Ferrous alloys- Mixture of one or more metals. At leats one of them containing iron and carbon.
- Non ferrous alloys- Mixture of two or more metals and niether of them containing iron and carbon.
Ferrous
Mild steel- Quite strong and cheap, but rusts easily and cant be hardened or tempered.
- Car bodies
- Nuts and bolts
High carbon steel- Harder than mild steel and cant be hardened and tempered. Difficult to work and rusts easily.
- Drills
- Tiles
- Chisels
- Saws
Cast iron- Hard, however brittle order impact.
- Machine parts
- Brake disks
- Engines
Non ferrous metals
Aluminium- Light wieght and corrosion resistant. Expensive and not as strong as steel.
- Aeroplanes
- Cars
- Ladders
Brass- Quite strong, corrosion resistant, malleable, ductile and looks good.
- Door furniture
- Etrical parts
Copper- Relatively soft, malleable and ductile and is a good electrical conductor.
- Wires
- Piping
Ferrtous alloys
- Stainless steel
- High speed steel
- Dies (tool) steel
Non ferrous alloys
- Brass
- Bronze
- Duralumin
Where does metal come from ?
Gold is the only metal that is extracted and usable without processing. The others are found in ores.
Metal ores
Copper- Chalcopyrite
Iron- Magneite, haematite
Tin- Cassiterite
Aluminium- Bauxite
Lead- Gralena
Zinc- Zinc blende
25% of the earths core is made out of ores. The more rare the more it costs. Aluminium is most common.
Iron (ferrite) converted from ore by heating. Impuraties (slag) removed from the surface. Cimbined with the carbon for more strength.
Steel- Iron and carbon. Amount of carbon determines strength. Alloymy increases properties. - Toughness and corrosion.
Carbon- Foud in the earth with is made from coal and iamond. Amount of carbon in steel determines strength and hardeness BUT increases how brittle.
More carbon= more hardness/ less ductile/ more brittle.
NON FERROUS= NO IRON !!!
Metal Melting piont (degress) Uses and properties
Aluminium 660 Kitchen weare, saucepans
Copper 1083 Water and gas pipes- wire
Gold 1063 Jewellery
Lead 330 Construction and roofing
Friday, 9 October 2009
Thursday, 8 October 2009
Metal Processes
Sheet Metal Bending
-A piece of sheet metal is placed into the bending machine.
-The sheet is placed into the v shaped die below the punch.
-The punch presses down and bends the material into a certain shape.
-The angle of the bend is determined by how far the punch moves.
-Metal up to 10mm thick can be bent cold on these machines.
CAD Plasma Arc Cutting
-Components are drawn in a CAD program such as Pro-Desktop.
-A nesting program is used to arrange the designs in a way which creates least waste.
-The designs are sent to the machine in DXF form.
-It cuts the material using a plasma-cutting torch.
-This is used to cut out sheet metal shapes for welded boxes etc.
-A piece of sheet metal is placed into the bending machine.
-The sheet is placed into the v shaped die below the punch.
-The punch presses down and bends the material into a certain shape.
-The angle of the bend is determined by how far the punch moves.
-Metal up to 10mm thick can be bent cold on these machines.
CAD Plasma Arc Cutting
-Components are drawn in a CAD program such as Pro-Desktop.
-A nesting program is used to arrange the designs in a way which creates least waste.
-The designs are sent to the machine in DXF form.
-It cuts the material using a plasma-cutting torch.
-This is used to cut out sheet metal shapes for welded boxes etc.
Monday, 5 October 2009
Man Made Boards and Finishes
Joint = Non-permanent - Assembly; Knock down fittings, mortive and tenon.
Fixing = Permanent, or semi-permanent; screw, nail, glue.
Finishes
Poly-Urethane - Seals and protects surfaces. Protects from wood stain!
Wood stain - Dyes material.
Oils - Oils are rubbed into material to maintain natural appearance.
Preservatives - Preservatives are used on wood thats used outdoors. Treating the wood with Tannelise (pressure treated and injected) can improve its lifespan upto four times. This makes it perfect for garden structures such as decking and gazebos.
Paint - Painting is one of the most commonly used wood finishes. The wood must be primed first so the paint has something to adhere to.
Man Made Boards
Man made boards have no moisture.
Plywood = The grains are opposite so the wood is strong in both directions.
Chipboard and MDF = These are both made similarly but MDF is made of fibres rather than chips. These can blunt tooling, as the glue used to stick them together is harder than the wood.
Hardboard = Cheap and easy to break. Its commonly used for the back of draws and wardrobes.
Blockboard = Made of blocks of scrap wood, and then a veneer of plywood is placed on either side making a sandwich style thing.
Man Made Boards have no flaws, they never bend or anything similar due to the lack of moisture. They are readily available and in the same size every time. 2240mm x 1120mm sheets, with 3, 6, 9, 12, 15, 18, 21 and 24mm thicknesses.. And this is consistent.
Fixing = Permanent, or semi-permanent; screw, nail, glue.
Finishes
Poly-Urethane - Seals and protects surfaces. Protects from wood stain!
Wood stain - Dyes material.
Oils - Oils are rubbed into material to maintain natural appearance.
Preservatives - Preservatives are used on wood thats used outdoors. Treating the wood with Tannelise (pressure treated and injected) can improve its lifespan upto four times. This makes it perfect for garden structures such as decking and gazebos.
Paint - Painting is one of the most commonly used wood finishes. The wood must be primed first so the paint has something to adhere to.
Man Made Boards
Man made boards have no moisture.
Plywood = The grains are opposite so the wood is strong in both directions.
Chipboard and MDF = These are both made similarly but MDF is made of fibres rather than chips. These can blunt tooling, as the glue used to stick them together is harder than the wood.
Hardboard = Cheap and easy to break. Its commonly used for the back of draws and wardrobes.
Blockboard = Made of blocks of scrap wood, and then a veneer of plywood is placed on either side making a sandwich style thing.
Man Made Boards have no flaws, they never bend or anything similar due to the lack of moisture. They are readily available and in the same size every time. 2240mm x 1120mm sheets, with 3, 6, 9, 12, 15, 18, 21 and 24mm thicknesses.. And this is consistent.
Natural Woods
Wood is fiberous with fibres running along the length of the trunk.
55% cellulose
28% lignin resin
Timber is therefore a natural reinforced polymer.
1. Harvesting: Cutting down the tree in the forest
2. Conversion: Cutting the trunk and large branches into boards, slab and quarter sawn.
3. Seasoning: Reduce the moisture content either naturul or kiln seasoned.
4. Board pred: Sawing to size and planing; PAR - Planed All Round.
Quarter Sawn:
55% cellulose
28% lignin resin
Timber is therefore a natural reinforced polymer.
1. Harvesting: Cutting down the tree in the forest
2. Conversion: Cutting the trunk and large branches into boards, slab and quarter sawn.
3. Seasoning: Reduce the moisture content either naturul or kiln seasoned.
4. Board pred: Sawing to size and planing; PAR - Planed All Round.
Quarter Sawn:
With quarter sawn there is more waste, but the sheets are more stable and less liable to warp. They also show much nicer grain structures.
Slab Sawn:
Slab sawing causes the wood to warp a lot more, but doesnt create as much waste.
When wood is sawn it is cut in inches, and when it is planed it is done in CM.
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