Shape & Form Metal Based Materials (AQA GCSE Design & Technology): Revision Note

How to cut metal

• Metals like mild steel, aluminium and copper are commonly cut in maker workshops by hand, or using a piece of machinery

• By hand, a maker can choose between:

  • A hacksaw

  • A junior hacksaw

  • Snips

• For a hacksaw or junior hacksaw, the metal will be mounted into a metal/machine vice tightly, and the saw will be used to cut the metal

  • The metal being cut is softer than the high carbon steel blade used in the saw

• For snips, the metal must be in sheet format, because a pair of snips are very similar to scissors

  • They are used to cut by “shearing” through the thin metal

• For machinery, vertical bandsaws can be used for cutting metals, a horizontal bandsaw is a dedicated saw which is used for large sections of metal, typically steel

How to drill metal

• To drill metals, a small number of additional steps are required which makes it different to the process of drilling timber

• Firstly, a hammer and centre punch are used to indent a small mark on the surface where the drill will locate to drill through the material

  • The tip of the drill bit will locate to the indent and prevent the drill entering the material in the wrong place

• Once there is an indent, the process of drill uses a high speed steel (HSS) drill bit

• Due to the density of metals like steel, it is more common to use a machine known as a pillar drill to drill the hole

How to turn metal

• The process of turning involves mounting a piece of round or square metal such as mild steel into the three jaw round or four jaw square chuck of a metal lathe

• A lathe is a machine that spins metal around an axis

  • This allows the maker to slowly feed cutting tools or drill bits into the material to remove it

• A metal lathe spins at such a high speed that coolant (usually oil) is needed to keep the metal and the cutting tool cool

  • This prevents overheating

• A metal lathe can help a maker to cut the cylindrical profile of metal, or drill holes in rounded bar

How to mill metal

• The process of milling involves mounting a block of solid metal such as mild steel into a machine vice

  • The machine vice is mounted to the bed of a milling machine

• The cutting tool, typically a square end mill

  • The cutting tool, which creates a flat bottom to the cuts it makes, is mounted into a chuck on the milling machine

• The cutting tool whilst spinning at high speed, does not move, instead the metal block mounted into the machine vice is moved

  • This creates cutting pathways or channelled cuts into the block below it

How to cast metal

• Casting is the process of turning a solid metal like steel, aluminium or pewter into a liquid by heating it to its melting point

  • The liquid is then poured into a mould or cavity, where it can cool and harden into a shape

• Sand casting involves the creation of a cavity or mould inside compacted sand

  • This has been shaped into the cavity inside a metal box

  • The liquid metal, typically aluminium, is poured into a hole into the sand and the cavity it will fill, called a runner

  • Once the liquid metal has fully filled the cavity in the sand, it rises up and out through a hole called a riser

  • Once cooled, the metal shape can be removed from the sand and cleaned

• Casting can also be carried out inside metal moulds in a process called die casting, which is very similar to polymer injection moulding

• Lower cost casting processes including casting a metal called pewter

  • Pewter has a relatively low melting point compared to other metals

  • It can be poured into ceramic, MDF or even cuttlefish mould cavities to make small parts

How to braze metal

• Brazing is the process of joining two metal parts made from the same material e.g. mild steel using a lower melting temperature “filler” metal

• The maker begins by shaping the two parts to fit closely together, and removing any rust or oil from the surfaces where the filler metal will go

  • Both parts have a flux chemical compound which prevents oxidisation to the joint area

• Once heated sufficiently, the filler material is put into contact with the metal, and will melt, flowing into the gaps on the join this flowing is known as capillary action

• The joint is allowed to cool, where the filler material cools and hardens, ready for filing

How to weld metal

• Metal parts such as mild steel can be welded using either gas welding or electric welding methods

• The gas or electrical heat is hot enough to cause not only the filler metal, but the parts being joined together, to melt

  • In brazing only the filler material will melt

• Welding therefore creates a much stronger bond between the two metal parts which have been welded