6. Machine Tools
Required performance:
6.1 Drilling machines
– Lists the uses of a drilling machine
– Explains briefly how drills are held in a machine
– Explains how a work piece is held in place, emphasizing dangerous practice and the particular problem when drilling thin plate
– Describes the procedure for inserting and removing drills with parallel and with tapered shanks
– Describes the care necessary to avoid accidents when using a drilling machine
– Uses drilling machines to acquire the fundamental skills of using them with sample materials provided
6.2 Grinding machine
Required performance:
– Explains the purpose of a grinding machine
– Explains how to use a grinding machine
– Demonstrates an awareness of the dangers which exist when using a grinding machine
– Describes the procedure to ensure safety when using a grinding machine
– Uses grinding machine to acquire the fundamental skills of using it with sample materials provided
6.3 Centre Lathe
Required performance:
– Explains the primary purpose of a centre lathe, its construction and Functions
– Explains the roles of each part, performing their functions of chucks, centres, face plates,
material removal, thread cutting and taper turning
– On a given diagram or machine, identifies the main features of a modern lathe
– On a given diagram or machine, indicates the features and dimensions which govern the capacity of a lathe
– Demonstrates an awareness of the dangers which exist when using a lathe
(Cutting tools)
Required performance:
– Explains various cutting tools in terms of materials
– Explains various cutting tools in terms of figures
– Explains various cutting tools in terms of functions
– Uses a centre lathe to acquire the fundamental skills of using it with sample materials provided
6.4 Welding and Soldering
Required performance:
a) Principles of electric arc welding
– Explains the suitability of low-, medium-and high-carbon steels for welding
– Sketches the relative positions of the electrode and the base metal when metallic arc welding manually
– States that A.C. welding is more common than D.C. welding
– Sketches the components and circuit necessary in arc welding
– Describes how welding electrodes are classified
– Describes the purpose of the electrode covering
– Explains how electrodes should be stored
– Explains how damp electrodes can be detected
– States how damp electrodes can be dried
– Identifies the tools commonly used when welding
– Describes the principle of metal arc gas-shielded welding
– Describes the principle of tungsten inert-gas welding
b) Principles of gas welding
Required performance:
– Explains the basic principles of gas welding
– Describes the principle features of a low-pressure system
– Explains what is meant by a high-pressure system
– Lists the fuel-oxygen/air mixtures
– Describes the flame produced when using oxygen and acetylene
– Explains the effect on the flame of mixing different proportions of oxygen and acetylene
– Describes the dangers of handling acetylene gas and the methods used for its storage in cylinders
– Explains why the maximum discharge rate should not be exceeded
– Identifies the safety fittings for an acetylene gas cylinder
– Compares the need for control of gas pressure for:
– welding
– cutting
– States that a two-stage gas pressure regulator gives a more precise control than a single-stage regulator
– Identifies the safety features of gas pressure gauges
– Sates that high-pressure blowpipes are unsuitable for use in a low-pressure system
– Identifies the principle parts of a high-pressure blowpipe
– Explains the care necessary for:
– blowpipe
– hoses
– Explains the purpose of hose check valves and flashback arresters
– Describes the sequence to be followed if a flashback arrester is triggered
– Explains the basic purpose of a cylinder manifold system
– Names the gas, states its approximate pressure and describes the cylinder outlet thread, given the colours of cylinders likely to be encountered
– Sketches the relative positions of the base metal, the filler wire and the welding nozzle when using:
– the leftward technique
– the rightward technique
– Demonstrates the welding procedure for both techniques in the above objective
– Explains the limitations of leftward welding
– Explains the advantage of the rightward technique
c) Welded joints in low-carbon steel
Required performance:
– Describes a butt weld
– Explains why plate edges are prepared
– Sketches cross-sections:
– of typical plate-edge preparations
– indicating the features of a good weld
– of a typical multi-run weld
– Describe a fillet weld
– Sketches cross-sections of fillet joints, showing:
– throat length with concave and convex reinforcement
– tee joint plate-edge preparations
– corner joints
– lap joint
– Makes welded butt and fillet joints, using manual electric arc and gas welding techniques
d) Common faults in welded joints
Required performance:
– Identifies the errors which can occur when lining up joints prior to welding
– Explains the cause of distortion
– Sketches a butt-welded and a fillet-welded joint, showing the effect of distortion
e) Thermal cutting
Required performance:
– States the applications of flame and plasma-arc cutting
– Explains the principle upon which oxygen is used to cut iron
– Describes the conditions necessary in order to cut when using an oxygen-fuel gas mixture
– Identifies the common engineering metals which can and cannot be cut using an oxygen-fuel gas mixture
– Lists the gases commonly used as fuels
– Identifies the controls on a gas cutting blowpipe and demonstrates their purpose
– Explains the factors which affect the quality of cutting
– States the basic principles of plasma-arc cutting
– Uses an oxygen-fuel gas cutting torch to cut straight lines and curves in mild steel plate up to 10 mm thick to crop mild steel sections
f) Inspection
Required performance:
– Constructs a checklist for visual inspection during:
– electric welding
– gas welding
– Constructs a list of the points to check visually after welding is completed
– Explains the limitations of visual inspection
– Carries out the following destructive tests on welded joints:
– bend
– macroscopic
– nick-break
– Carries out penetrant tests on welded joints
– Describes the principle of:
– ultrasonic inspection
– microscopic inspection
– Lists common weld defects and their causes
g) Soldering
Required performance:
– Explains why brazing is used
– Describes the basic principles of soldering
Soft soldering
Required performance:
– Explains the limitations of soft-soldered joints and the reasons
– Explains how soft-soldered joints might be strengthened
– With the aid of a simple sketch, describe the uses of a soldering iron
– States the main hazards and precautions necessary when soldering
– Tin is a soldering iron and makes soft-soldered joints
– Describes the process of sweating joints
– Explains the need for a flux, its application and its removal
– Explains the differences between and the uses of the following fluxes:
– passive
– active
– Explains the differences between (including the approximate melting temperatures) and the uses of:
– plumber's solder
– tinman's solder
Hard soldering
Required performance:
– State the reason for hard soldering
– Identifies the metals which can be joined by:
– Silver solder
– brazing
– Bronze welding
– States the processes to be followed, stating the approximate melting point when:
– Silver solder
– brazing
– Bronze welding
– Makes soft-and hard-soldering joints
h) Safety and health when welding
Required performance:
– States the protective clothing to be worn when welding on a bench
– States the additional protection necessary when welding in more difficult situations
– States the measures necessary to protect other personnel when welding
– States the precautions related specifically to gas welding
– Explains the effect of radiation from welding on the eyes and skin
– Describes the dangers of fumes from welding and how this should be dealt with
– Explains the principles of the precautions to be taken when welding or when a similar heating process is to be performed in tanks which have contained combustibles
– States the precautions to be taken when working in confined spaces
– States the care and precautions necessary when handling and storing compressed gas cylinders, with particular reference to acetylene and oxygen