742 - Metalwork

Introduction to the Workshop

Workshop layout. Safety rules and regulations related to personnel, equipment and all others.

Hand Tools

Introduction to common hand tools: their uses, care and safety precautions to be observed when using them.

(a) Layout and Measuring Tools

(b) Holding Devices

(c) Drills

(d) Reamer

(e) Cutting Tools

(f) Hammers

(g) Wrenches

Metals

History of metals (metals in the service of man). The occurrence of metallic ores in the earth. Obtaining, concentrating and leaching of ores.

Production of metals. The structures of furnaces, and their operations.

Ferrous metals: production, basic composition. Wrought iron, plain carbon steels, alloys steels, grey cat iron, aluminum alloys, zinc alloys

Properties of metals: Tensile strength, compressive strength, shear strength. Toughness, elasticity, plasticity, ductility, malleability, hardness, corrosion resistance, conductivity, fusibility.

Heat Treatment: terms and definition. Hot and cold-working.

Non-Ferrous Metals: non-ferrous alloys, high copper content, copper based. Production of aluminum and its alloys. Tin-based alloys.

Non-metallic materials: natural, e.g. rubber, glass, wood, emery, ceramics, synthetics, e.g. plastics (thermo-setting, plastics, thermoplastics, laminated plastics). Properties of plastics: electrical insulation, strength/weight ration, corrosion resistance.

Sheet Metalwork

Marking out techniques; cutting with tinsnips (hand-shears); bending (seams, folding joints, etc.); the use of soft-faced hammers. Punching, drilling and riveting. Setting out of job, creasing and wire cutting with bench shears, and safety precautions. Construction of cylindrical and conical-shaped objects. Compound sheet metalwork (two or more parts joined together).

Hammered Metalwork Process

(a) Sinking, hollowing, raising, expanding, contraction, planishing

(b) Finishing and decorative work, wiring, engraving, piercing, response work, etching, polishing.

(c) Enameling

Metal Joining

(a) Soft Soldering; simple soldering exercise using tin plate; heating, cleaning and tinning. Application of solder to bits and use of fluxes.

(b) Hard Soldering: Use of brazing hearth, preparation of work; spelters and application, fluxes (types and application). Types of flame and method of operation of brazing torches.

Welding Practice

(a) Oxy-acetylene: welding of mild steel

- Definition: fusion joining process and safety precautions.

- Equipment: high pressure gas cylinders, goggles, gas regulators, nozzles and choice with type and size according to jobs.

- Techniques: setting up equipment, selection of nozzles, lighting of the flame, opening sequence of cylinders, adjustment of working pressure, observing effect of various flames, edge preparation, tacking light steel plate and making butt welds, closing sequence.

(b) Metal Arch Welding

- Definition of the method and safety precautions

- Equipment: introduction to the equipment, the welding set and action of high voltage, the protective shield, welding rods and types and their suitability for various jobs.

- Techniques: setting up equipment, adjustment and selection, of electrodes, welding simple joints on mild steel lap joint, butt corner welds.

(c) Introduction to resistance welding and brief description of joining certain other metals such as aluminum, brass, cast iron, galvanized steel noting particular problems likely to be encountered and their remedies.

Power Tools

Portable power tools, e.g. hand drills.

The Centre Lathe

Introduction to lathework, its construction and safety precautions, fixing of tools in tool post, adjusting cutting speeds, feed and depth of cut by hand, simple turning between centers, face plate, parallel turning, facing, drilling and center drilling exercise limited to use of three-jaw chuck. A standard of accuracy of 0.25 mm may be required.

Drilling Machines

The construction and types of drilling machines: the bench type and pedestal drill; methods of holding drill bits, various methods of a clamping job including the use of parallel strips; changing speeds and importance of cooling. Twist drills, structure, use, maintenance.

Grinding Machines

This section should be only introductory with emphasis to safety precautions and the practical exercise should be limited to grinding of single point tools such as lathe tools, chisel and drill bits, making reference to importance of cutting angles.

Care and Maintenance of Tools

(a) Cleaning of files with wire brush.

(b) The importance of maintaining share edges and faces of measuring tools undamaged.

(c) Oiling of some tools with moving parts including lubricating the vice bench, calipers.

(d) Maintenance of cutting angles and sharpness of tools, such as chisels, drill bits, scribers, punches, etc.

(e) Metal identification of sparks produced while grinding.

Measuring Techniques

(a) The use of various types of calipers: outside, inside, odd-leg hermaphrodite and vernier calipers up to 0.1 mm.

(b) The micrometer.

(c) Surface plate.

(d) Surface gauge (scribing block).

(e) The use of angle plate (fixed and adjustable).

(f) Limit gauges.

(g) Care and maintenance of high accuracy measuring tools.

Finishing Processes

Polishing, draw filing, bluing, oiling, painting.

Forge Work

This will be carried out by manipulation of mild steel in the forge and anvil. Students will be expected to know all equipment. The exercise will include: safety precautions, importance of observing correct temperature; other things will include bending, twisting, fullering, swaging and drawing down. Punching, drifting, upsetting, hot cutting, flanging and setting.

Foundry Work

This will involve dealing with casting equipment and it will be limited to sand molding and core sand mixtures. Casting of simple objects in aluminum alloys and lead. Safety precautions with emphasis on dealing with molten metal.

Screws Cutting by Hand

Introduction to types of threads including I.S.O. metric threads. The importance of coarse and fine threads; B.S.W., B.S.F., B.A., Square, Acme and Buttress thread. Use of rectangular held die (nut) and circular split die and their adjustment. Importance of countersinking and chamfering the work to be threaded. The use of screw gauges and lubrication.

Heat Treatment of Steel

Definition of heat treatment. Various heat treatment processes in the workshop. Definition of: hardening, tempering, normalizing, annealing and case hardening. Tools and equipment, e.g. furnaces and importance of heat treatment in the steel rolling industry.

Industrial Manufacturing Processes

The objective of this component is to familiarize the candidates with industry. The student is therefore expected to have had adequate understanding of the relationship between technological development an the social change. The impact of technology on industry, assembly live production, industrial pollution and job opportunities for the society in industry.