1. Metal Processes
This PowerPoint presentation takes you through the various metal work processes that you are required to be familiar with in order to successfully complete the unit.

2. Turning
Turning is the production of cylindrical components using a centre lathe. The material is held firmly in a rotating chuck whilst a cutting tool is brought towards it to create the required shape. A variety of processes can be carried out on the lathe for example turning cylinders, creating texture (knurling), accurate drilling and threading

3. Milling Machine
Milling machines are powerful pieces of equipment which use rotating multi toothed cutters to shape the material. There are two types of milling machine, horizontal and vertical. The machines are named by the position of the cutting tool in relation to the workpiece. Milling machines can be used as side and face cutters and can also be used to cut slots in the material.
Milling consists of machining metal by using rotating cutters which have a number of cutting edges. These tools are known as milling cutters.
Vertical Milling Machine
Horizontal Milling Machine

4. Milling Cutters
Slot Cutter
Slot
Straddle Milling

5. Milling Cutter
Dovetail Slot
Dovetail Cutter
Angled Face
Angle Cutter

6. Milling Cutters
T-Slot
Tee Slot Cutter
Flat Surface
Slab Cutter

7. Die Casting
Where large quantities of quality castings are required in industry, the moulds (‘dies’)need to be permanent. These special, alloy moulds are costly to produce because they are made in sections for easy removal of the components. The high operating costs involved make this process economically viable for high volume mass production where accuracy of shape, size and surface finish is essential.
Gravity Castings
Molten metal is poured into the cavity under its own weight. This produces sound, dense castings with mechanical properties superior to pressure casting (since metal enters the mould with less turbulence). This process also traps less gas than pressure casting does, leading to less porosity.

8. Die Casting
‘Hot’ chamber and ‘cold’ chamber processes are used. In both processes molten metal is forced into a metal die by a hydraulic ram. Thin section and complex shapes with fine detail are possible.
die
fixed pattern
injection piston
molten metal
release
cavity
1. A measure of molten metal is poured into the charge chamber.
2. An injection piston then forces the metal into a water-cooled die through a system of sprues and runners.
3. The metal solidifies rapidly and the casting is removed, complete with its sprues and runners.

9. Die Casting
Materials
Materials used in this process include low melting temperature alloys, lead, zinc, aluminium and brass alloys.
Identifying Features
Section hair lines, ejector pin marks, flashes caused by leakage left on internal surfaces (these do not interfere with performance or appearance), and sprue and runner marks.

10. Press Forming
Press forming involves squeezing sheet metal between two matched metal moulds (dies). This gives a very strong, shell-like structure. One die is the mirror image of the other, apart from an allowance for he thickness of the material being formed. The machining of these dies is a specialised skill. They can be complicated and therefore difficult and time consuming to make. This makes them very expensive to produce.
The Process
The sheet metal component starts out as a flat sheet or strip
1 A blank is cut to the required size.
2 The blank is placed in a press.
3 The product is formed using immense force.
The complete forming process may take several additional stages of
operations to form, draw (stretch) and pierce the material into its final shape

11. Press Forming Materials
Sheet metals; various steels, aluminium alloys, brass, copper
Identifying Features
Sudden directional changes, i.e. sharp edges and deep draws, are avoided to minimise overstretching the walls of the product. Different operations, e.g flanges, ribs, piercing, can be identified.
Uses
Products used in many everyday activities are easily identifiable. These range from pans, kettles and stainless steel kitchen sinks to car bodies and aircraft panels.

12. Sand Casting
Sand casting is the most frequently used metal casting process. ‘Green, foundry sand is a blend of silica grains, clay and water. The term ‘green’ describes the damp quality which bonds the sand together. Oil-bound sand gives excellent results but is relatively expensive and difficult to reconstitute. There is an element of waste involved as the sand that is in contact with the hot metal will burn. This burned sand needs to be scraped out and disposed of.
The quality of the casting produced depends on the quality of the pattern. These are normally made in wood. The pattern requires radiused corners, drafted sides and a good surface finish. The sand mould is produced around the pattern, which is removed to leave a cavity. Molten metal is poured into the mould and solidifies. When cold, the mould is broken up to retrieve the casting.

13. Sand Casting 1. Place the pattern centrally in the drag.
sprue pins
cope
drag
gates
riser
runner
1. Place the pattern centrally in the drag.
2. Pack sand around the pattern.
3. Turn the drag over and attach the cope.
4. Insert sprue pins and pack sand around them.
5. Remove the sprue pins.
6. Split the moulding box and cut ‘gates’.
7. Remove the pattern to leave a cavity.
8. Reassemble the cope so that the mould is ready to receive the molten metal.
9. Pour the molten metal into the runner. The melt fills the mould and exits, along with any gases, via the riser.

14. Sand Casting Materials
Iron, aluminium and non-ferrous alloys are most widely used in sand casting. Exceptions include refractory (able to withstand high temperatures) metals such as titanium. Precious metals e.g. gold lend themselves to casting.
Identifying Features
Complex 3-D components. Mainly solid but internal shapes can be produced using cores. Thin sections are difficult to mould. Surface texture can be poor. Draft angles, fillets, rounded corners and strengthening webs will be evident and will echo the pattern requirements. Other recognisable features include bosses and porous surface textures. Fettle marks, due to the removal of runners and risers, may be visible.
Uses
Casting is a versatile process using the material properties in the manufacture of engine parts, tools and decorative jewellery. Multiple mould patterns decrease production time thus lowering production costs.

15. Casting Casting in Aluminium
The main reason for casting an object is that the shape of the object is such that it would make matching either very difficult or too expensive.
There are many ways in which an object can be cast, but there are only two ways which are suitable for use in the school workshop.
1. Gravity feed casting
2. Investment casting.
The main difference being that gravity feed casting uses a wooden pattern and so can be used for large numbers, where as investment casting uses either a wax or a polystyrene pattern and therefore only be used once. Both these methods come into the category of Green sand moulding, which gets its name not from the colour of the sand, but because the sand is damp.

16. Piercing and Blanking The Process
Piercing and blanking are essentially the same process, involving the stamping of shapes out of sheet metal or metal strip. The differences in the process simply depend on which bit of metal is to be kept: in piercing a shaped hole is made in the metal, whereas in blanking a shape is stamped out of the metal and then used.
The Process
Piercing
The punch and die are shown here in the closed position. Notice how the punch fits into the die but does not enter it, stopping instead as soon as the metal has been cut. Accurate alignment of the two is essential.
punch
strip
die

17. Blanking
Blank falling through die
and bolster plate
Bolster plate
Die
Ram
Metal Strip
Punch
Stripper
Blanking
The main components used for blanking in mass production are a punch, a die and a stripper plate. The stripper plate prevents the metal ‘riding up’ the die on its upward travel. The die is attached to the main press by means of a bolster plate. The punch is attached to a movable ram.

18. Progressive Piercing and Blanking
Many products requires to be both pierced and blanked. This is often done in the same press by first piercing the metal, and then moving it along to another die and blanking out the desired shape. This process is called progressive piercing and blanking.
1 The metal strip is fed into the first die.
2 A hole is pierced in the metal on the first stroke of the ram.
3 The ram rises and metal is moved into position over the blanking die.
4 Accurate alignment is essential here.
5 The punch descends and the completed component ( in this case a washer) is blanked from the metal strip. At the same time a hole is pierced in the next washer.
6 Piercing is normally done before blanking, as this minimises the risk of fracturing the metal.
Ram
Blanking
punch
Piercing punch
Pilot
Scrap
Stripper
Stop
Metal Strip
Die
Finished Washer
Metal Strip

19. Piercing and Blanking Materials
Most types of metals can be pierced and blanked in sheet or strip form. The metal is normally annealed first so as to minimise the risk of fracture or tearing.
Identifying Features
A sheared surface will show two distinct areas of deformation and fracture. With the correct clearance angles in the punch, this can be minimised to give a reasonably smooth edge which will require no further finishing.
Uses
Uses of piercing and blanking include component parts for a variety of tool and products. Often products made from sheet metal that have been press formed are pierced to give a decorative finish.

20. Drop Forging The Process
Impression-die drop forging is an industrial process used in the production of high quality, strong metal components or products. The main advantages are that components can be accurately repeated using specially shaped dies to control the flow of metal; the need for highly skilled craftsmen is thus eliminated.
The Process
The die used are very expensive to produce. High alloy steels are required to prevent heat loss which causes them to wear too quickly under impact loads.
1. A hot metal billet is placed between the dies.
2. The hot metal is forced into the cavity using a power driven hammer. (Note that the process may take more than one operation using a succession of dies.)
3.Excess metal is squeezed out forming a flashing around the parting line of the two dies. The amount of flashing is determined by die wear and the quantity of excess metal.
4. When the forging is complete the flash is removed using a trimming die.
PRESSURE
Anvil
Ram
Top Die
Bottom Die
Billet
Flash

21. Drop Forging Materials
Most metals are in alloy form are suited to the drop forging process. Alloy steels and copper alloys are most common.
Identifying Features
The function of the product may indicate that drop forging is the most appropriate process for manufacture, i.e. the product or certain parts of the product may require compressive or tensile force to be used. Strength to weight ratio is a consideration. Visually there may well be evidence of flashing and flash removal around the edges of the product. Quality products may have undergone further finishing to eliminate visual evidence of die parting lines.
Uses
Drop forging metal increases its strength. The grain structure of the metal is changed to follow the outer contour of the component. This provides greater scope for the design of high quality metal products. Examples range from hand tools such as spanners and plumbing fittings to high quality cutlery and domestic appliances.

22. Drawing Punch Pressure ring
The process of drawing is the main process in the production of three dimensional curved pressings e.g. drinks cans. The sheet material (blank) is held in place by a pressure ring which has a highly finished surface plus lubrication to minimise friction. A punch is then forced into the material drawing it down to form the required shape. The depth which can be drawn in one punch depends on the type of material, its tensile strength and the tool design.
Pressure ring
Punch

23. Joining Materials
The manufacture of most products requires joining together of materials. Part of the designer’s role is to select the most appropriate method.
Permanent joining methods include adhesives, arc welding, fitted joints, riveting, spot welding.
Non-permanent methods include nuts, bolts and screws.

24. Welding
Soldering, brazing and welding techniques are used mainly to join metals. Some thermoplastics can also be joined in this way.
Arc Welding
Heat is obtained by an electric arc via a transformer. One lead is attached to the work and the other to a grip holder a welding rod. An arc is formed when the end of the rod is brought near the work. The heat melts the parent metal and the filler rod together. The rod is coated with flux to prevent oxidation.

25. Spot Welding
The metal is heated and fused together between two copper electrodes. Used on thin gauge mild steel, e.g. car bodies

26. Riveting
There are two methods. The traditional method uses soft iron, aluminium or copper for snap, countersunk and flat head rivets in conjunction with a hammer and rivet ‘set’.
Traditional 2. 1. 3. 5. 4.

27. Riveting
Where the use of a hammer is to be avoided, controlled pressure is applied to a ‘pop rivet’ using a pop-riveting ‘gun’. Also used for ‘blind’ riveting. 1. 2. 3.
The rivet pliers are pushed on to the pin of the rivet and the handles are pulled together. As this happens the pin head is pulled into the rivet and the end of the rivet is expanded. Eventually the pin will break off leaving the rivet permanently fixed in position holding the two pieces of plastic / aluminium together.
The pop rivet is passed through both holes in the sheet plastic / aluminium.
The two pieces of plastic or aluminium are drilled to a size slightly larger than the rivet

28. Bolts
The screw thread has the advantage of enabling items to be taken apart for inspection or maintenance purposes. Nuts, bolts and set screws can be obtained in various forms. There are numerous designs of spanners for use with square- and hexagonal-headed nuts and bolts, just as there are keys for socket screws.

29. Screws
Screws are used to fasten together boards, panels and fittings such as hinges and brackets. Pieces can be taken apart and reassembled without damage. Screwdrivers are available in a variety of blade types, e.g. slot and pozidrive. Effort in driving screws home can be minimised by using electrically powered ‘screw guns’

30. Other Things To Consider
Permanent, semi-permanent or temporary?
Types(s) of material(s)
allow for movement
surface area
indoor or outdoor?
Are cramps to be used?
Time (setting time)

31. Finishing Finishing bright steel : Oil finishing black steel:
Stage 1 - After shaping with coarse file and smooth file, complete filing by draw-filing. Always work in the same direction along the metal and make sure that each stage removes all marks left by the previous one.
Stage 2 - Finish by using different grades of emery cloth, first coarse, then fine, and finally after all marks have been removed add a little oil to the fine cloth for final finishing
Stage 3 - To protect the metal from rust, smear it with light grease.
Oil finishing black steel:
Stage 1 - Remove all loose scale from forging, grease, etc.
Stage 2 - Either dip the metal in machine oil and burn it into the metal, or heat the metal to dull red heat and quench it in oil.
Stage 3 - Wipe off surplus oil and polish with black boot polish.

32. Finishing Stage 1 - Thoroughly clean, polish and degrease the metal.
Painting metal:
Stage 1 - Thoroughly clean and degrease the metal. Paraffin or special degreasers will clean badly affected parts while hot water with soda or detergents will remove light oil and dirt.
Stage 2 - Find a dust free place to work, and make arrangements for supporting the work while painting and drying before starting.
Stage 3 - For maximum protection apply primer, undercoat and topcoat. For inside work one or two coats of topcoat alone are adequate. Two thin coats are always better than one thick one.
Lacquering:
Stage 1 - Thoroughly clean, polish and degrease the metal.
Stage 2 - Apply the lacquer or varnish with a best quality soft brush to preserve the finish.