Standard Grade Craft & Design Metals Standard Grade Craft & Design

Metals: A definition Metals form the major portion of the Earth’s elements. Metals are categorised as Ferrous or Non-Ferrous. Ferrous metals contain iron as the base metal.

Alloys Alloys are mixtures of metals and/or other elements combined together. Ferrous alloys range from plain carbon steels, with 98% iron to high alloy steels, with up to 50% of other elements. Ferrous alloys, particularly steels, form 90% of the world’s total metal usage. This is because of their low cost and versatility which is brought about by hardening and tempering.

Forms of Metal Metals are produced in variety of forms, e.g. rod, bar, flat strip, tube, angle and various channel sections. These forms are available in a vast range of sizes because it is difficult to change the size of any piece of metal – it takes a lot energy to cut or soften.

Ferrous Metals Iron is the basis of all ferrous (iron –bearing) alloys. Pure iron is of little practical use as a material. Alloying refers to the bringing together of two or more metals, often with other additive elements to improve properties and characteristics of the new material

Ferrous Metal Properties Name Composition Properties and characteristics Users Cast Iron Iron + 3.5% Carbon Brittle/hard skin Machine tools, vices Mild Steel Iron + up to 0.35% carbon malleable/ ductile uniform texture Nuts, bolts, screws, tubes, girders, car bodies High Carbon Steel Iron + up to 1.5% carbon malleable/ ductile, can be hardened and tempered Cutting tools, files, drills, saws, knives, hammers, taps and dies

Non – ferrous metals This group of metals does not contain iron and therefore will withstand most moist conditions. Common examples are – Copper, aluminium, tin and lead Precious metals such as gold and silver

Non – Ferrous Metals Name Composition Properties and characteristics Uses Aluminium Pure metal produced Good strength to weight ratio, casts easily Window frames, pots and pans Copper Pure metal Ductile and malleable, low melting point, expensive Central heating pipes, electrical wiring/cable, jewellery Tin Heavy/soft, low melting point Bearings, solder, coating sheet steel Lead Heavy/soft/ weak, ductile/ malleable, low melting point, can be cast Roof flashing, solder Zinc Weak, difficult to work with Galvanising

Malleable that can be hammered, pounded, or pressed into various shapes without breaking: said of metals capable of being changed, molded, trained, etc.; adaptable

Ductile that can be stretched, drawn, or hammered thin without breaking; not brittle: said of metals easily molded; plastic; pliant easily led; tractable

Other Non-ferrous alloys Brass (copper and zinc) Bronze (copper and tin)

What’s special about aluminium? Aluminium is one of the most economical and sustainable metals in use today. It is produced using renewable hydro-electricity and aluminium can be recycled repeatedly, saving both energy and the cost of primary production.

What’s special about copper? Copper is the most important electrical conductor and is also the base metal in brass and bronze alloys. Copper possesses three important properties, namely high electrical and thermal conductivity; high ductility and as illustrated in the case of the Statue of Liberty high corrosion resistance.

Past Paper practise Why when designing a stem for a lamp would you use a malleable wire? Suggest a suitable metal for this wire? What is meant by the term non-ferrous? What is meant by the term alloy? Electrical wires are made from a ductile metal. Name a suitable metal for the wires? Describe what is meant by ductile? An alloy was one of the materials used in the construction of a pot. Explain what is meant by the term alloy? Only one part of the pot is made from a material which is a conductor of heat, state which part and suggest a suitable metal? The other parts of the pan are made from non-conductive materials. Name a suitable non-conductive material?

Metal work lathe

The centre Lathe The centre Lathe The Centre Lathe is used to manufacture cylindrical shapes from a range of materials including; steels and plastics. Many of the components that go together to make an engine work have been manufactured using lathes. These may be lathes operated directly by people (manual lathes) or computer controlled lathes (CNC machines) that have been programmed to carry out a particular task. A basic manual centre lathe is shown below. This type of lathe is controlled by a person turning the various handles on the top slide and cross slide in order to make a product / part.

The centre Lathe – Facing off A very basic operation is called ‘facing off’. A piece of steel has been placed in the chuck and the lathe cutting tool is used to level the end. This is done by turning the cross-slide handle so that the cross-slide moves and the cutting tool cuts the surface of the steel. Only a small amount of material should be removed - each pass of the cross slide. After each pass of the cutting tool the top slide can be rotated clockwise to move the tool forward approximately 1mm. This sequence is repeated until the steel has been levelled (faced off). When using a centre lathe it is always advisable to work patiently and safely. Do not attempt to removed too much material in one go. At best this will caused damage to the steel being worked on and to the expensive cutting tool being used. At worse an accident will occur

TURNING A SHORT TAPER When turning a short taper the topslide is set a the required angle. This is normally done by loosening two small allen screws and then rotating the topslide to the angle and tightening back up the two allen screws. When the chuck is rotating the topslide handle can be rotated slowly by hand in a clockwise direction. A small amount of metal is removed each time until the taper is formed. If too much steels stands out from the chuck the steel will vibrate and the surface finish will be very poor.

Drilling on a centre lathe The tailstock of a lathe can be used for drilling, with the aid of a drill chuck attachment. The drill chuck has a morse taper shaft which can be push into the shaft of the tailstock, locking it in position. The usual starting point for drilling with a centre lathe is to use a countersink bit. This is used to drill slightly into the material and creates a starting point for other drills that are going to be used. Attempting to drill with a traditional drill bit without countersinking first will lead to the drill bit slipping straight away. It is not possible to drill a hole successfully or safely with out using a centre drill first. If a long piece of material has to be turned on a lathe then a centre drill is used to produce the hole at one end. This allows the drilled end to be supported by the tailstock centre

How to use a Knurling tool: A knurling tool is used to press a pattern onto a round section. The pattern is normally used as a grip for a handle. Apprentice engineers often manufacture screwdrivers. These have patterned handles, to provide a grip and this achieved through the technique called knurling. The pattern produced is called a ‘knurled pattern’. This diagram shows the knurling tool pressed against a piece of round section steel. The lathe is set so that the chuck revolves at a low speed. The knurling tool is then pressed against the rotating steel and pressure is slowly increased until the tool produces a pattern on the steel.