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Answers to exercises

Exercises I

1. a) Manufacturing industry produces goods today, using machines, computers, and automation, in such an efficient manner, that the need for hand tools has been almost eliminated.

b) Hand tools are used for making prototypes and models, and in the main• tenance of equipment c) Maintenance work refers to the work that needs to be done, to keep ma• chines and equipment, in good working condition.

d) A centre punch may be used to mark a point on a metal, before drilling. e) A pin punch may be used to drive in or remove, straight pins, tapered pins, and keys. f) An offset screw driver is used to reach screws in places which cannot be reached with an ordinary screw driver. g) A ring spanner surrounds the head of a bolt completely, and therefore has a much firmer grip on the head of a bolt than an ordinary spanner, which surrounds the head only partially.

h) A hacksaw consists of an adjustable frame, fitted with a removable blade. i) A scraper is used to remove small amounts of metal, from high spots on a metal surface.

j) Chisels have to be ground to a definite shape, so that they work effi• ciently and do not become too hot. 138 Answers to exercises

2. a) A hammer can be used for shaping and forming sheet metal. b) A centre punch can be used to mark a point on a piece of metal before drilling. c) Pliers are used for many purposes, like gripping, and holding.

d) A spanner is used for tightening nuts and bolts.

e) Files are used to remove metal from the surface of an object. f) The cut of a file refers to the distance between the teeth. g) The important angles of a chisel are the rake angle, and the clearance angle. h) Taps are used for cutting internal screw threads. i) Dies are used for cutting external screw threads.

3. a) Although most goods are manufactured today using automatic machines, hand tools are still required for repair and maintenance work. b) A hammer is a multi-purpose tool. One of its uses among others, is to hammer a piece of metal until it acquires the required shape.

c) An offset screw driver is a special tool. It is used for reaching screws in awkward places.

d) There are many types of spanners. When a bolt has to be gripped firmly, one uses a ring spanner or a socket spanner.

e) A metal saw which is used for cutting sheet metal is called a hacksaw. A piece of metal can be made to acquire a desired shape, by working on it first with a chisel, and then with a file. Answers to exercises 139

Exercises ll

1. a) A workshop contains all the types of equipment which are necessary to carry out the work required.

b) A workshop bench is a table on which the work and tools can be placed, and on which work can be done.

c) Holding and clamping devices are needed to hold an object firmly, while work. is being done on it.

d) Vee-blocks are devices which are used to hold cylindrical rods and pipes, while work is being done on them.

e) Angle blocks are used when the position of the workpiece needs to be changed by 90°. f) Marking-out equipment is used to scribe lines, circles, etc. on an object, before work is done on it.

g) A marking-out table is a strong table with a very flat metal surface. h) Measuring devices are needed for checking the dimensions of the fm- ished work, and also during the marking-out process.

i) The usual accuracy of a micrometer is about one-thousandth of a centi- metre. j) An engineer's square can be used to check whether two surfaces are at right angles to each other.

2. a) A workshop contains many types of equipment.

b) A workshop bench is a strong table on which we can place the work, and the tools, that are required.

c) A vice is clamped to the table by means ofbolts and nuts. 140 Answers to exercises

d) Vee-blocks are used to hold rods or pipes, while work is being done on them. e) Angle blocks have two surfaces which are at right angles to each other. f) Special fixtures are used when accurate machining, welding, or assem- bly work is required. g) Marking-out equipment is used to scribe lines on an object. h) Measuring instruments are used for checking the dimensions of objects. i) A micrometer is an accurate measuring instrument.

j) An engineer's square is used to check if two surfaces are at right angles to each other.

3. a) A mechanical workshop contains different types of equipment. Among these are holding and clamping devices, and also measuring devices. b) It is necessary to mark out a casting by scribing lines, before work can be done on it. c) Special fixtures are required, when accurate machining or assembly work has to be done. d) Measuring instruments are used in the marking-out process, and also for checking the dimensions of an object after work has been done on it. e) A micrometer is an instrument which can be used to measure lengths, to an accuracy of 1/1000 em. f) An engineer's square is used to check whether two surfaces are at right angles to each other. Answers to exercises 141

Exercises lll

1. a) Cans, razor blades, kitchen utensils, aeroplanes, and automobile bodies, are some of the articles that can be made of sheet metal.

b) Hand shears are used for cutting thin metal sheets, while bench shears are used for cutting thicker metal sheets.

c) Complex shapes can be cut quickly, by using presses and press tools.

d) Automatic presses are used to cut and form complicated shapes in sheet metal, quickly, and efficiently.

e) Bending rollers are used to roll sheet metal into cylindrical shapes. f) Bending machines are usually used to make simple straight folds in metal sheets. g) A flanging operation produces edges of various widths and angles, on flat or curved sheets.

h) Beading improves the strength, stiffness, safety, and appearance, of an article made from sheet metal.

i) In the wiring process, the edge of a piece of sheet metal is folded round a wire of suitable diameter. j) Folded metal joints are often soldered to make them water-tight.

2. a) A large variety of articles are made from sheet metal today.

b) Simple tools are still used for sheet metal work, although machines do most of the work today.

c) Thick sheets of metal can be cut using bench shears. d) A handsaw can be used to cut complex shapes from metal.

e) In large scale manufacturing industry, automatic presses are used for sheet metal work. 142 Answers to exercises

t) A press tool consists of two parts, a punch, and a die. g) Flanging produces edges of various widths and angles on metal sheets.

h) The joining of thin sheet metal is often done using folded joints. i) In the wiring process, the edge of a piece of sheet metal is folded round a wire. j) Bending machines make simple straight folds on metal sheets.

3. a) Most of the articles produced by industry today are produced by auto• matic machines. However, simple tools are still used for many purposes. b) The cutting of thin metal sheets can be done using hand shears, but for cutting thick sheets, bench shears are needed. Complicated shapes can be cut individually using a handsaw. c) Large scale production of metal components in industry is done by using automatic presses. Presses can also be used for punching out complicated shapes. d) Bending rollers are used to shape metal sheets into a cylindrical form, while bending machines are used to make simple straight folds. e) Beading is a process by which folded edges of different widths can be produced. Answers to exercises 143

Exercises IV

1. a) Metal fasteners are used to join metal sheets or metal components by mechanical means. b) Riveting is useful when metal sheets have to be joined together perma• nently. c) Fasteners with screw threads are used to join components, which have to be taken apart later. d) An additional part like a spring washer or a lock nut may be used, to prevent a bolt and nut from becoming loose. e) Set screws often have a hexagonal hole in their head, so that they can be tightened efficiently by using a hexagonal key. f) Studs are used in brittle materials like cast iron. g) If a bolt is tightened excessively in a cast iron thread, the screw thread can be damaged. h) Studs are used to hold down a cylinder head on the cylinder block of an automobile engine. i) Studs are used to ensure water-tight joints. j) It is not possible to use bolts and nuts when only one side of the parts to be joined is accessible.

2. a) Metal components can be joined together by using metal fasteners. b) Riveting is used on ship's hulls and aircraft fuselages.

c) Metal parts can also be joined by fastening devices which have a screw thread. d) When both sides of the parts to be joined are accessible, nuts and bolts maybe used. 144 Answers to exercises

e) It is often necessary to use set screws with countersunk heads. f) Countersunk screws often have a hexagonal hole in their head. g) Studs are used in applications where heavy pressures are encountered. h) Studs are used to join components to cast iron, because the tensile strength of cast iron is very low

i) The screw thread in a cast iron component may crumble if tightened ex• cessively. j) It is necessary to remove the head of a motor car engine, when the en• gine needs overhauling.

3. a) Metal components and sheets can be joined in many ways. One way is by the use of metal fasteners like rivets or bolts and nuts. b) Bolts and nuts can be used when both sides of the components to be joined are accessible. An additional part like a washer could become necessary if the parts are subject to vibration. c) Bolts with normal heads can be used to join metal components, how• ever, it is often necessary to use bolts with countersunk heads. Such bolts have a hole of hexagonal shape in the head, which enables the bolt to be tightened very effectively using a hexagonal key.

d) Studs are used in applications where heavy pressures are encountered, and also where water-tight or gas-tight joints are needed.

e) Studs are used to join the cylinder head of an automobile engine to its cylinder block. The joint between the cylinder and the head has to be a temporary one, because it is necessary to remove the head, when the en• gine needs reconditioning. Answers to exercises 145

Exercises V

1. a) Soldering is the process of joining two metal objects by a third soft metal alloy, which is called solder. b) Solder is a metal alloy which melts at a lower temperature than the met- als being soldered. Two types of solder are commonly used, soft solder, and hard solder. c) The surfaces of the metals must be thoroughly cleaned before soldering. d) The fluxes usually used in the workshop are acidic in character. e) Acid fluxes are corrosive and unsuitable for electrical work, and resin is usually used as a flux instead. f) In the brazing process much higher temperatures are reached, and the solder usually used is spelt. g) In oxy-acetylene welding, a blowpipe through which oxygen and acety- lene gases flow in suitable amounts, is used.

h) In the electric arc welding process, the metal electrode acts as a filler rod, making the process easier to control. i) In the resistance welding process, no filler rods or filler electrodes are required.

j) A large amount of heat is generated at the contact faces, because the re- sistance to the flow of current is large.

2. a) The process of joining two metal surfaces by a third soft metal alloy, is called soldering.

b) Hard solder is an alloy of copper and zinc, and is called spelt or silver solder. c) Flux removes oxides and grease from the metal surface, and allows the solder to flow freely. 146 Answers to exercises

d) Fluxes used in the workshop are usually acidic in character, and are cor• rosive.

e) The solder used for electrical work is in the form of a wire with a resin core.

f) The hard soldering process uses spelt as the solder, and borax as the flux.

g) The two principal types of welding are, electric arc welding, and resis• tance welding. h) In oxy-acetylene welding, a blowpipe through which oxygen and acety• lene gases flow through is used. i) The filler rod melts, and a small amount of liquid metal is formed at the joint.

j) In the electric arc welding process, the metal electrode also acts as a filler rod.

3. a) Solder is a metal alloy, which melts at a somewhat lower temperature than the metals to be joined. Two types of solder are normally available. One type of solder which is an alloy of tin and lead, is softer than the other, which is an alloy of copper and zinc, and is called silver solder. b) It is very important that the surfaces of the metals that have to be sol• dered, should at first be thoroughly cleaned. For this purpose, a flux which removes oxides and grease from the surface is used.

c) In the hard soldering process, another solder and more heat must be used to reach the melting point of hard solder, which is about 600°C. A hard soldered joint is considerably stronger than a soft soldered one. d) The temperature of the flame in an oxy-acetylene blow pipe can reach a maximum value of about 3000°C. The blowpipe heats the metal parts that have to be joined, and also a filler rod which is held in the flame at the joint. Answers to exercises 147

e) In the resistance welding process, the surfaces of the metal parts which are to be welded, are pressed against each other, and a large current is passed through the joint. During this time, a lot of heat is generated at the contact surfaces . 148 Answers to exercises

Exercises VI

1. a) Industry needs different types of materials for different purposes. b) Wrought iron has the advantage that it can be easily bent, and formed into different shapes.

c) Mild steel is a general purpose low carbon steel that can be used for many purposes, like reinforcing concrete, making containers, car bodies, etc. d) Carbon steels are steels with a high carbon content. Carbon steels lose their hardness when they become hot under working conditions, and are therefore unsuitable for use as metal cutting tools. e) Alloy steels contain alloying elements like tungsten, chromium, and va• nadium, and can work at higher temperatures than carbon steel. f) Cast iron is iron with a higher carbon content than steel, and has the ad• vantage that it can be easily cast into complex shapes. g) The important nonferrous elements and alloys are copper and its alloys, aluminium and its alloys, and zinc and its alloys. h) Plastic goods have the advantages of being cheap, light, and easy to manufacture.

i) Thermoplastics become soft when heated, and become hard on cool• ing.They can be moulded easily, and have the advantage that they can be repeatedly remoulded. Thermosetting plastics are harder than ther• moplastics, but can be heated and moulded only once. j) A good example of a composite material is resin reinforced with fibre• glass. It has the advantages of high strength, and easy mouldability, at room temperature.

2. a) Different kinds of metals and alloys are used for different purposes. Answers to exercises 149

b) Wrought iron has the advantage of being easily bent into different shapes. c) Steel is an alloy composed of iron and a small amount of carbon. d) Carbon steel can be hardened, and is used to make small tools like scis• sors, and screw drivers. e) Metal cutting tools are made of special alloy steels called high speed steels. f) Tools made of alloy steels can work at higher temperatures than tools made of carbon steel. g) Cast iron when in a liquid state, flows easily into moulds. h) Thermosetting plastics become soft when heated, and can be moulded into different shapes. i) Composite materials can be made from resins reinforced with glass fi• bre. j) Mild steel can be used for reinforcing concrete and for making car bod• ies.

3. a) Metal alloys and plastics are amongst the most important materials used by manufacturing industry today. Different kinds of metals and alloys are required for different applications. b) Mild steel which contains about 0.2% carbon, is the most used type of steel, and is used for many purposes, like the reinforcing of concrete, and the construction of water tanks. Mild steel, unlike steels with a high carbon content cannot be hardened.

c) Cast iron is a very useful material, because in liquid form it is able to flow easily into moulds. Complex shapes can be cast using cast iron. Cast iron is a hardwearing material which resists abrasion. d) Plastics are of increasing importance, because goods made of plastics are easy to manufacture, reasonable in price, and light. Some plastics 150 Answers to exercises

become soft when heated, and hard when cooled. Such plastics can be used repeatedly. e) Composite materials, which are made of resin and glass fibre, can be used, where high strength, and easy moulding at room temperatures, are some of the properties required. Answers to exercises 151

Exercises VII

1. a) Casting is probably the quickest and the most economical way of pro• ducing a metal component. b) In sand casting, the molten metal is poured into a hollow space in a box filled with sand. The hollow space has the shape of the object that has to be cast. c) A pattern is a replica of the object to be cast, and is usually made of wood or steel. d) The three main stages in the manufacture of a casting are, the making of the pattern, the making of the mould, and the pouring in of the metal. e) The casting is usually made slightly larger than the final object that has to be produced, so that it can be machined to a precise size. f) Sand casting is particularly useful for producing large complex castings, like machine beds, and engine cylinder blocks.

g) The two main die casting processes are, gravity die casting, and pressure die casting. Die castings are stronger, and better finished, than sand castings. h) Die casting moulds are made out of steel. i) The die casting process has the disadvantage, that it can only be used with low melting point metals and alloys.

j) Many automobile components like carburettors, fuel pumps, and engine cylinder heads, are manufactured by the die casting process.

2. a) The process of casting has been practiced for thousands of years.

b) In the sand casting process, the molten metal is poured into a mould. c) The pattern which is a replica of the object to be produced, is made of wood or metal. 152 Answers to exercises

d) The wooden pattern is usually made in two halves, which are joined together by dowel pins. e) The pattern and the resulting casting, are usually made larger than the final size of the finished object. f) The extra allowance in the size of the casting, is called a machining al• lowance. g) The two methods of producing castings are called gravity die casting, and pressure die casting. h) Die casting moulds are very precisely made, and the castings produced are very accurate in their dimensions. i) The disadvantage of the die casting process is that, only low melting point metals and alloys can be used. j) In the pressure die casting process, the molten metal is forced into the dies under pressure.

3. a) The process of casting is probably the quickest and easiest way to pro• duce metal objects, particularly large and complex objects. b) In the sand casting process, the melted metal is poured into a hollow space filled with sand. The hollow space is similar in shape and size to the object that has to be cast. c) The pattern and the casting are usually larger than the finished metal component. This extra allowance is called a machining allowance. d) Moulds which are used in the pressure die casting process are made of steel, and can be used indefinitely. The moulds are precisely made, and the castings produced are very accurate in their dimensions. e) The disadvantage of the pressure die casting method is that only low melting point metals and alloys, like zinc and aluminium alloys can be used in this process. However, the castings produced by this process have the advantage that they do not need to be machined. Answers to exercises 153

Exercises Vlli

1. a) The purpose of the heat treatment process, is to improve the properties of metals to the extent that the manufacturing process is made easier, and also to enable the metal component to be able to withstand rough usage. b) The mechanical properties of metals, like hardness, strength, and brittle• ness, depend on the grain structure of the metal. c) The size, shape, and orientation of the grains, affect the mechanical properties of metals.

d) Castings that are allowed to cool slowly have a coarse grain structure, while castings that are allowed to cool rapidly, have a fine grain struc• ture. e) Objects that have a fine grain structure, are stronger than those which have a coarse grain structure.

f) Mild steel sheet is produced by a cold rolling process. This process changes the grain structure of the steel, causing the grains to become elongated. g) Mild steel sheet is in a work-hardened state after rolling. h) Metal pressings are initially in a work-hardened state, and very brittle. They will break easily during usage, if they are not subjected to heat treatment. i) Stress relieving is done by heating the component to about 500°C, and allowing it to cool. It has the advantage that it is relatively cheap, and that no scale is formed on the metal surface. j) In the annealing process, the steel component is heated to a higher tem• perature than in the normalizing process, and allowed to cool slowly. This makes the steel as soft and ductile as possible. 154 Answers to exercises

2. a) The purpose of heat treating a metal is to improve its properties. b) Metals consist of a large number of small crystals interlocked together. c) The mechanical properties of metals depend on the size, shape, and ori• entation of the crystals in the metal.

d) In the sandcasting process, the metal cools slowly, resulting in a casting with a coarse grain structure.

e) The pressure die casting process produces castings that are accurate, and well finished.

f) Mild steel sheet is produced by a process, which causes the grains in the metal to become elongated. g) Metal components which are produced from mild steel sheet are in a state of stress. h) Stress relieving is relatively cheap, because only a small amount of en• ergy is required for this process. i) Stress relieving has the further advantage, that the surface is not spoilt by the formation of scale on it. j) The annealing process goes further than the normalizing process, and makes the steel as soft and ductile as possible.

3. a) The heat treatment process improves the mechanical properties of a metal to the extent that the manufacturing process is made easier. In addition, a heat treated metal component is able to withstand rough us• age. b) The mechanical properties of a metal like hardness, strength, and brit• tleness, depend on the size, shape, and orientation of the crystal grains in it. c) When a casting is produced, the grain structure of the casting depends on the rate at which it cools when it is solidifying. If the rate of cooling Answers to exercises 155

is slow, as in a sand casting, the crystal grains are large. On the other hand, if the rate of cooling is rapid, the crystal grains are somewhat smaller. d) Metals are often in a highly stressed state after the manufacturing proc• ess. This stress must be removed, before the component is put into use. This can be accomplished by heating the component to a temperature of above 500°C, and allowing it to cool. e) The process of annealing makes a metal as soft and ductile as possible. Here the metal component is heated to about 850°C as in the normaliz• ing process, but allowed to cool at a much slower rate. 156 Answers to exercises

Exercises IX

1. a) The cheapest way of producing complex metal components is by cast• ing. b) Forged components are stronger, and less brittle, than cast components. c) No material is wasted in the forging process, because the entire material is forced into the shape of the final component. d) Cast iron cannot be forged, because it becomes very brittle, and breaks easily when heated to red heat. e) A blacksmith produces forged components by using hand tools. f) Mechanical hammers were used for forging after the beginning of the industrial revolution. They have the advantage of being able to forge large components. g) Three ways in which a forging can be produced are, hand forging, drop forging, and upset forging. h) The drop forging process is particularly useful, when a large number of medium-size forgings are required. i) In the drop fotging process, the red hot metal billet is forced into the cavity between the dies. j) In the upset forging process, a change in the cross-sectional area of the component is produced.

2. a) Metal components can be made cheaply, and efficiently, by the casting process. b) Cast components are usually brittle, and break easily. c) Forged components are stronger than cast components, or those pro• duced by machining. Answers to exercises 157

d) Forging is more economical in the use of material, because the metal is forced into shape. e) Mild steel becomes ductile at high temperatures, and can be forced into the right shape. t) Forged components were produced in small quantities by blacksmiths. g) Large mechanical hammers were used to produce large forgings. h) Two half dies are used in the drop forging process, and the red hot billet is forced into them.

i) Often, several stages of forging are needed, to produce a forged compo• nent. j) In upset forging, the cross-sectional area of the component is changed.

3. a) Metal components can be produced more cheaply by casting than by forging. Components produced by casting however are very brittle, and break easily. b) The process of forging is very economical in the use of material, be• cause the metal is pressed into the form of th(l fmal component, and no metal is wasted. c) Steel and many metals become ductile at high temperatures, and can be pressed or hammered into the desired form. Cast iron cannot however be forged in this way. d) The method of drop forging is particularly useful, when a large number of components need to be produced.

e) In this process two half dies are used. The pressure exerted by the upper die, forces the red hot billet into the cavity between the dies. 158 Answers to exercises

Exercises X

1. a) Carbon steels having a carbon content of about 0.8% to 1.3% can be hardened. b) Only the working part of a tool is usually hardened.

c) In the hardening process, a tool is heated to a temperature of about 820°C at which temperature it acquires a cherry-red colour.

d) The next stage in the process, is the quenching of the tool in water or oil. e) The process of removing some of the brittleness is called tempering, and if this is not done, the tool will break easily. f) Tempering reduces the hardness of the cutting edge of the tool, while increasing its toughness. g) A hardened object can be tempered by heating it to a temperature of be- tween 230°C and 320°C. h) When the surface of a hardened object is polished first and then tern- pered, a coloured oxide film is formed on the surface. i) As the tempering temperature increases, the tool loses hardness, while gaining toughness.

j) Case hardened steel has a hard surface, and a tough interior.

2. a) Tools made of high carbon steel can be hardened. b) Only the working part of a chisel, which is its edge, is hardened. c) The edge of the chisel is heated to a temperature of 820°C, until it be- comes cherry red in colour. d) The chisel is quenched by plunging into water or oil. e) The edge of the chisel will be very hard, and also very brittle. Answers to exercises 159

t) The process of tempering, toughens the edge of the chisel.

g) The colour of the surface film depends on the temperature to which it is heated.

h) As the tempering temperature is increased, the tool loses hardness, while gaining toughness.

i) The surface colour gives a good indication of the properties of the tool after tempering.

j) If mild steel is heated to 820°C, and then immersed in a carbon rich substance, it absorbs carbon on its surface.

3. a) When a tool like a chisel is hardened, only the working part, which is the edge of the chisel is hardened.

b) The edge of the chisel is heated to about 820°C, at which temperature it acquires a cherry red colour. After this it is immersed in water or oil.

c) The tool is now very hard, but also very brittle .It is necessary to reduce the brittleness, otherwise the chisel will break under normal conditions of use.

d) The process of reducing the brittleness is called tempering. To temper a hardened object, it must be heated to a temperature of between 230°C and 320°C, depending on the material used. The process of tempering makes the tool tougher, and ensures that it does not break under normal conditions of use.

e) It is often an advantage for an object to have a hard outer surface, and a tough interior. A case hardened component has a carbon rich outer sur• face, which can be hardened, while the interior retains its normal tough• ness. 160 Answers to exercises

Exercises XI

1. a) In rotatory motion, the object is rotating round an axis, or a point.

b)~ In reciprocating motion, the object moves along a straight line in one direction first, and then back along the same straight line, to its starting point.

c) A shaft is usually a cylindrical rod which undergoes a rotatory motion.

d) Bearings are supports in which a shaft is able to rotate.

e) Bronze or white metal are suitable materials for making plain bearings.

f) A split bearing is a plain bearing which is made in two halves.

g) The bearing on the small end of a connecting rod, is a single piece hol• low cylindrical bearing. h) A ball bearing consists of hardened steel spheres, running between two precision ground hard cylindrical races. i) The purpose of lubrication is to maintain a thin film of oil between two contact surfaces. j) Two rotating shafts can be coupled together, by using gear wheels, by using a belt and pulleys, or by using a chain and sprocket wheels.

2. a) A rotating body is usually rotating round a point or an axis.

b) A body has linear motion when it moves in a straight line in one direc• tion.

c) The support in which a shaft rotates, is called a bearing.

d) The big end bearing of an automobile connecting rod, consists of two thin split bearings.

e) The spheres in a ball bearing are fitted between two cylindrical races. Answers to exercises 161

t) The process of maintaining a film of oil between two contact surfaces, is called lubrication.

g) Two shafts may be coupled using a belt and two pulleys.

h) The small end bearing on an automobile connecting rod is called a gudgeon pin.

i) The rollers in a roller bearing, are located between an outer cup and an inner cone.

j) Two shafts may be coupled using a chain and two sprocket wheels.

3. a) When a body has a rotatory motion, it usually rotates round an axis in a clockwise, or an anticlockwise sense. If the motion is linear, the body moves in a straight line.

b) A machine is composed of many parts, some of which are moving. A shaft is a cylindrical rod, which is usually made of steel, and is sup• ported by bearings in which it can rotate.

c) Bearings are usually in the form of plain bearings, ball bearings, or roller bearings. Special alloys are used to make plain bearings, for ex• ample, bronze.

d) Ball bearings are composed of steel balls located between two cylindri• cal races. The lubrication of such bearings is simple, because they only need an occasional application of grease.

e) A rotating shaft has mechanical energy. It is often necessary to transfer this energy to another shaft. This can be done by using two gear wheels, or by using two pulleys and a belt. 162 Answers to exercises

Exercises XII

1. a) Gears are used to transmit motion from one part of a mechanism to an• other. b) The ratio of the speeds between two shafts can be changed, by changing the ratio of the number of teeth in the gear wheels. The direction of the axes of rotation can be changed, by using special gears like spiral gears.

c) Spur gears have teeth which are cut parallel to their axes of rotation. They are used to couple parallel shafts. d) In a bevel gear, the teeth lie on a conical surface, and appear to meet at the apex of a cone. e) Helical gears are gears whose teeth lie on the surface of a cylinder, and are inclined at an angle to the axis of rotation of the gears. f) Spur gears are simple and cheap to make, but can only transmit motion between two parallel shafts. Bevel gears are able to transmit motion be• tween two shafts inclined at an angle to each other, but are more expen• sive to make. g) Helical gears are placed in an oil bath, to minimize wear on their teeth. h) A rack and pinion is a device, which converts rotatory motion into linear motion.

i) Worm gears are used for heavy duty work, where a large ratio of speeds is required. j) Gearboxes are used, when several changes in the ratio of the speeds be• tween two shafts are required.

2. a) Gears transmit motion from one part of a mechanism to another. b) A spur gear has teeth cut parallel to its axis of rotation. Answers to exercises 163

c) The larger gear wheel is called the gear, and the smaller gear wheel the pinion. d) The teeth in a bevel gear lie on a conical surface, and appear to meet at the apex of a cone.

e) The teeth in helical gears are cut on a cylinder, and at an angle with the axis of the cylinder. f) Helical gears are usually placed in an oil bath, in order that wear may be minimized. g) A rack and pinion converts rotatory motion into linear motion.

h) Worm gears are used for heavy duty work, where a large ratio of speeds is required. i) Helical gears are quieter, and smoother in operation, than spur gears.

j) When two gears mesh together, the ratio ofthe speeds of the shafts, de• pends on the ratio of the number of teeth in the gears.

3. a) A gear wheel when coupled with other gear wheels, transmits motion from one part of a mechanism to another. b) In helical gears, the friction, and the resulting heat and wear generated, are greater than with other drives. These are often placed in an oil bath in order to reduce wear. c) In a bevel gear, the teeth are cut in such a way, that they lie on a conical surface, and appear to meet at the apex of a cone. d) The teeth of a helical gear are cut on a helical cylinder, at an angle to the axis of the drive. Helical gears are quieter, and run more smoothly, than spur gears. e) When two gears which are attached to two shafts are coupled together, the ratio of the speeds of the shafts, depends on the ratio of the number of the teeth on both gear wheels. 164 Answers to exercises

Exercises Xlli

1. a) Screws are used for fastening metal and other types of components. b) A screw thread is a ridge in the form of a spiral, on the surface of a cyl• inder or a cone. c) There are many types of screw threads, each designed for a particular type of work. d) The pitch is the distance from a point on a screw thread, to a corresponding point on the next thread, measured parallel to the axis of the screw. e) The lead ofthe screw, is the distance advanced by the screw, when it is rotated by one revolution. The lead is equal to the pitch multiplied by an integral number. f) This is the distance measured radially over which a mating male and fe• male thread overlap. g) The major diameter is the largest diameter of the screw thread, and the minor diameter is the smallest diameter of the screw thread. h) Threads may be produced by cutting, by rolling, or by grinding. i) Machine tools have tapered holes in their spindles, so that tapered shanks of small tools like drills, can be fitted into them. j) The angle of a thread, is the angle between the two inclined faces of the thread.

2. a) Screws are commonly used for fastening metal components. b) A screw thread is in the form of a spiral on the surface of a cylinder, or a cone. c) There are many types of screw threads, each suitable for a different kind of work. Answers to exercises 165

d) The pitch is the distance from a point on a screw thread, to the corre- sponding point on ,the next screw thread.

e) The lead is the distance advanced by the screw in one revolution.

f) In a double thread screw, the lead is twice the pitch.

g) The major diameter is the largest diameter of the screw thread, and the minor diameter is the smallest diameter of the screw thread.

h) Screw threads can be cut using taps and dies, or by using a lathe.

i) Most machine tools have revolving spindles, which have tapered holes in them.

j) The taper on the inside of a spindle matches exactly, the taper on the outside of the tool which is fitted into the spindle.

3. a) An external screw thread is cut on the outside of a cylinder, while an in• ternal screw thread is cut on the inside of a hole, like a nut.

b) There are many types of screws threads, each suitable for a particular type of work. Each screw thread is made to a definite specification, and has a special name, for example, a metric screw thread.

c) The pitch, is the distance between a point on a screw thread, to the cor• responding point on the next thread. The lead, is the distance by which the screw advances, when it is rotated through one revolution.

d) In a single thread screw, the pitch and the lead are the same. In a double thread screw, the lead is double the pitch.

e) Most machine tools have revolving spindles with tapered holes in them, into which the tapered shanks of drills can be fitted. The taper on the tool, matches exactly the taper on the inside of the spindle. 166 Answers to exercises

Exercises XIV

1. a) It is difficult to drill the right size of hole in the right place, because a drill usually produces too large a hole, and also because the positioning of the hole is difficult.

b) A compound table is a table which has movements at right angles to each other. The work is moved using the lead screws on the compound table, until the position of the hole is precisely located under the drilling head, after which the drilling is done.

c) A centre drill, is a short stiff drill, with a short pointed part which does not bend easily.

d) The different parts of a drill are the body, the shank, and the tang. e) Small drills are held in a self-centering chuck. f) Large drills are inserted into the spindle of the machine. g) A sleeve is used, when it is necessary to use a drill with a small shank, in a machine with a large hole in its spindle.

h) A drift is a tool used to remove drills from the spifidle of a machine. i) A reamer is used to finish a hole accurately to size.

j) Counterboring opens the end of a hole cylindrically, while countersink• ing opens the end of a hole conically.

2. a) The accurate drilling of a hole of the right size at the right location, can be difficult.

b) A compound table has two movements at right angles to each other. c) A centre drill is first used to start a new hole.

d) A twist drill is made from a cylindrical piece of steel, and has got spiral grooves. Answers to exercises 167

e) Small drills have straight shanks, and are held in a self-centering chuck. f) Larger drills have tapered shanks, and are fitted directly into the spindle of the drilling machine.

g) A tool which is used to remove a drill from a spindle is called a drift. h) A hole can be finished precisely to the required size, by using a reamer. i) Counterboring is the process of enlarging the end of a hole cylindrically.

j) Countersinking generates a cone shaped enlargement of the end of a hole, into which the head of a countersunk screw can fit.

3. a) Although drilling a hole appears to be a simple operation, the accurate drilling of a hole of the right size, and in the right place, can be very difficult. A large variety of machines, and tools, have been developed for the drilling of holes.

b) A drill is usually made from a cylindrical piece of HSS steel, and has spiral grooves. At the beginning of the drilling process, a centre drill is used to drill a small hole. Then a twist drill is used to drill the hole to the right size. c) Small drills have cylindrical shanks, and are held in a self-centering chuck. Larger drills have tapered shanks, which enable them to be in• serted quickly into the spindle of a machine.

d) Not all tapered drills have shafts of the same size. When it is necessary to fit a drill with a small shaft into a spindle with a large hole, a sleeve is inserted between the shaft and the spindle.

e) A drill does not produce an accurately sized hole in a metal. The inside surface of the hole is rough, and is slightly oversize. This difficulty can be overcome by drilling the hole slightly undersize, and finishing the hole with a reamer. 168 Answers to exercises

Exercises XV

1. a) Many types of metal cutting machines, like lathes, and shaping ma• chines, use single point metal cutting tools. b) The pointed part of the tool acts as a wedge which presses on the body of the metal, and tears off a chip when the metal moves relative to the tool.

c) For efficient metal cutting, the tools should be made of the right mate• rial, and have the correct cutting angles ground on their tips. d) The important angles on a lathe tool are, the top rake angle, the side rake angle, the front clearance angle, and the side clearance angle. e) Clearance angles are necessary to ensure that, only the edge of the tool touches the work. f) If the angles on a tool are incorrect, more heat is generated, tool wear is increased, and the surface finish of the work is made worse. g) The use of a cutting fluid reduces the heat generated during the cutting process, and thus increases the life of the tool. h) Water soluble oils are cheap and efficient coolants, but do not have good lubricating properties.

i) Water soluble coolants are unsuitable for complex operations such as gear cutting.

j) Carbide tipped tools are very hard, and will maintain a sharp edge under conditions which cause ordinary tools to bum away.

2. a) Many metal cutting machines like lathes, and shaping machines, use single point cutting tools.

b) It is absolutely essential that the cutting angles on a tool are correct. Answers to exercises 169

c) The cutting action in which metal chips are removed, is similar to the action of a chisel.

d) The pointed part of the tool is like a wedge which presses heavily on the metal, and tears off a chip.

e) Clearance angles are necessary to ensure, that only the edge of the tool touches the work.

f) Changing tool angles has an effect on the heat generated, and on tool wear.

g) When fast spindle speeds are used, a small amount of cutting fluid is pumped over the cutting edge of the tool.

h) The cutting fluid helps to remove chips from the edge of the tool, and improves surface finish.

i) Water soluble oils are cheap and efficient coolants, and are suitable for the machining of most steel components.

j) Water soluble coolants do not have good lubrication properties, and are unsuitable for gear cutting.

3. a) The cutting process by which metal chips are removed from a metal, is similar to the action of a chisel. b) For efficient metal cutting, it is absolutely necessary that the tools are made of the right material, and have the right cutting angles. The cutting angles are different for different materials, on which cutting has to be done.

c) Clearance angles are necessary to ensure that, only the edge of the tool touches the work. If there was no clearance angle, the tool would not cut, but only rub on the work.

d) The use of a coolant, reduces the heat produced during the cutting proc• ess, and this increases the life of the tool. The coolant also helps to re• move metal chips, from the cutting edge of the tool. 170 Answers to exercises

e) Water soluble oils are cheap and efficient coolants, and are suitable for machining most steel components. However they do not have good lu• bricating properties, and are unsuitable for complicated machining op• erations, like gear cutting. Answers to exercises 171

Exercises XVI

1. a) Engineering inspection is important, because it is necessary to check whether manufactured components have the right dimensions. b) Variations in dimensions must be kept within strict limits, to ensure the interchangeability of parts.

c) Nominal dimensions are the dimensions given on the drawing of the component.

d) The deviation from a nominal dimension is called a tolerance, and this is necessary, because it is impossible to produce a large number of components, having precisely the dimensions given in the drawing. e) The two limits between which the dimensions of a component lie, are called the low limit, and the high limit. f) In a clearance fit, a shaft must be able to move freely in a hole, without being loose in it. g) When the allowed deviation or tolerance is only above, or only below, the nominal dimension, then it is called a unilateral tolerance. If the de• viation can be on both sides of the nominal dimension, then it is called a bilateral tolerance. h) The engineering allowance is the difference in dimensions between the high limit of the shaft, and the low limit of the hole. i) Allowances and tolerances must be kept as large as possible, otherwise the number of rejected components will be high, and this will increase the manufacturing cost.

j) An interference fit occurs when a shaft is slightly larger than a hole, and can only be forced into the hole under pressure.

2. a) Engineering inspection is an essential part of all manufacturing, but it is not usually possible to inspect every component. 172 Answers to exercises

b) Small deviations in dimensions must be kept within strict limits. c) Limits are necessary to ensure that components are interchangeable. d) The dimensions of a component given in the drawing, are called nomi• nal dimensions.

e) It is impossible to produce components, which have precisely the di• mensions stated in the drawing.

f) A certain amount of deviation from the nominal dimensions must be al• lowed, and this is called a tolerance.

g) In a clearance fit, the shaft must be able to move freely in a hole, with• out being too loose in it. h) The engineering allowance, is the difference between the high limit of the shaft, and the low limit of the hole.

i) Small tolerances, increase the cost of manufacture, and also the number of rejected components. j) If the shaft is made slightly larger than the hole, pressure is required to force the shaft into the hole.

3. a) Although engineering inspection is an essential part of engineering pro• duction, it is not possible to inspect every manufactured component.

b) When a component is designed, it is given certain dimensions on the drawing which are called nominal dimensions. However it is not possi• ble to manufacture a large number of components, that have precisely the dimensions given on the drawing.

c) For this reason, a definite deviation from a nominal dimension is al• lowed, and this is called a tolerance. When a component is manufac• tured, each dimension must lie between two values, called the high and low limits.

d) For a shaft to be able to enter a hole, there must be a small difference between the upper limit of the shaft, and the lower limit of the hole. This difference is called an allowance. Answers to exercises 173

e) In general tolerances must be kept as large as possible. Small tolerances increase the manufacturing costs, and also the number of rejected com• ponents. 174 Answers to exercises

Exercises XVII

1. a) A lathe can be used for machining cylindrical and conical surfaces, and also for cutting screw threads. b) The accuracy of the work done on a lathe, depends on the accuracy of the lathe itself, and also on the skill and accuracy of the operator. c) A lathe is unsuitable for production work, because a lot of time is taken for tool setting, tool changing, etc.

d) It is mainly used for the making of prototypes, and in maintenance work. e) The main parts of the lathe are the bed, the headstock, the tail stock, and the carriage. f) The headstock has a strong spindle which is driven by an electric motor through a gearbox. g) The work is usually held in a chuck. h) The purpose of the tool post is to hold the cutting tools, and it is fixed to the carriage. i) Capstan and turret lathes have the same headstock and fourway toolpost as ordinary lathes. The tailstock is however replaced by a hexagonal turret. j) Each face of a hexagonal turret holds tools which are used successively, to perform different operations in a regular sequence.

2. a) Lathes can produce components that are symmetrical about an axis. b) The accuracy of the work done on a lathe, depends on the skill and ex• perience of the operator. c) The ordinary lathe is not suitable for production work, because a lot of time is spent on tool setting. Answers to exercises 175

d) It is only used in tool rooms and workshops for the making of proto• types and for maintenance work. e) The lathe has a rigid bed, on which are mounted a fixed headstock, and a movable tailstock. t) The speed of the spindle can be varied through a wide range. g) The work to be machined is held in a chuck. h) The work is turned down to the desired dimensions. i) The carriage can move along the guideways of the bed, in a direction parallel to the axis of rotation of the headstock spindle. j) The headstock contains a strong spindle, driven by an electric motor through a gearbox.

3. a) A lathe can be used to turn cylindrical surfaces both external and inter• nal, and also to turn conical surfaces. An additional feature of the lathe, is its ability to cut screw threads on a cylindrical surface. b) The accuracy of the work done on a lathe depends on the skill and expe• rience of the operator. A lot of time is required for tool setting and tool changing, with the result that this type of work is not suitable for production. c) The lathe has a rigid bed with parallel guideways, on which are mounted a fixed headstock, and a movable tailstock. In addition, it has a carriage which can be moved along the guideways, in a direction parallel to the axis of rotation of the spindle. d) The headstock has a strong spindle, which is driven by an electric motor through a gearbox. The speed of rotation of the spindle can be varied through a wide range, to suit the work that has to be machined. e) The work that has to be machined must be held in a device called a chuck, which is fitted to the front end of the spindle. When the spindle rotates, the work rotates with it, and can be turned down to the desired dimensions, using single point tools which are held in a tool post. 176 Answers to exercises

Exercises XVIII

1. a) A planer is primarily used to produce plane surfaces.

b) In a shaper, the work is fixed on a table, and the metal is removed by a single point metal cutting tool.

c) The time taken for the return stroke is reduced by using a quick return mechanism. The reason for doing this is to reduce the machining thne. d) Shapers can generate flat, horizontal, vertical, or inclined surfaces. They can also generate contoured surfaces.

e) Very heavy workpieces cannot be machined on a shaper. f) The tool in a shaper performs a reciprocating motion.

g) The fundamental difference between a shaper and a planer, is that in a shaper, the work is fixed and the tool moves, while in a planer, the tool is fixed and the work moves. h) The most widely used type of planer is the double housing planer. i) The rigidity of a double housing planer is ensured, by joining the two housings at the top by a cast iron member.

j) The table of the planer may be driven mechanically or hydraulically.

2. a) A shaper is used to produce flat surfaces.

b) In a shaper, the work is fixed on a table, and metal is removed from its surface by a single point metal cutting tool.

c) Metal is removed only during the forward cutting stroke, and not during the return stroke.

d) The time taken by the return stroke is reduced by using a quick return mechanism. Answers to exercises 177

e) A machine tool like a shaper, is used primarily to produce plane sur• faces. f) A planer is large compared with a shaper, and is capable of machining heavy workpieces. g) In a planer the tool is fixed, while the work performs a reciprocating motion. h) There are many types of planers, of which the double housing planer is the most commonly used. i) The two vertical housings are joined by a cast iron member, to ensure stability. j) There are two more tool heads mounted on the vertical faces of the housings.

3. a) In a shaper, the work is fixed on a table, and is machined using a single point cutting tool. Metal is removed during the forward stroke, and no metal is removed during the backward stroke. b) To reduce the machining time, it is necessary to reduce the time taken by the return stroke. This is ensured, by using a quick return mechanism. c) The shaper is chiefly used to produce flat surfaces. The surfaces can be vertical, horizontal, or inclined. In addition, it can be used for producing slots, gear wheels, and irregular surfaces, using specially shaped tools.

d) A planer is used like a shaper, to produce flat surfaces. A planer is large and massive in comparison with a shaper and is able to machine work• pieces which are too heavy to be fixed on the work table of a shaper. e) The fundamental difference between the shaper and the planer, is that in a shaper, the work is fixed and the tool moves, while in a planer, the tool is fixed and the work moves. 178 Answers to exercises

Exercises XIX

1. a) Lathes use single point cutting tools, while milling machines use mul• tipoint cutting tools.

b) The multipoint cutting tools used in milling machines, achieve fast rates of metal removal, and also produce a good surface finish.

c) Ordinary milling machines have three independent movements, longi• tudinal, transverse, and vertical.

d) Ordinary milling machines lack the rigidity required for heavy produc• tion work.

e) A horizontal milling machine receives its power from a motor, through belts, gears, and clutches.

f) On a horizontal milling machine, milling cutters are mounted on the ar• bor of the machine.

g) The vertical milling machine has a column and knee like a horizontal milling machine, but has a spindle which is vertical, and can be swiv• elled through an angle.

h) In a universal milling machine, the table can be swivelled, and moved at an angle to the milling machine spindle.

i) Accessories like dividing heads, vertical milling attachments, rotary ta• bles, etc. can be fitted to a universal machine.

j) These accessories enable the machine to produce gears, twist drills, milling cutters, etc.

2. a) Milling machines use single point cutting tools, and not multipoint cut• ting tools.

b) The work table has three movements, longitudinal, transverse, and vertical. Answers to exercises 179

c) Ordinary milling machines lack the rigidity required for heavy duty work.

d) The use of multipoint cutting tools, enables the machine to achieve fast rates of metal removal.

e) The spindle just projects out of the column face, and has a tapered hole in it.

f) Cutting tools and arbors, can be fitted into the hole in the machine spin• dle.

g) The overhanging arm mounted on the top of the column acts as a bear• ing support for the arbor.

h) The spindle receives power from the motor, through belts, gears, and clutches.

i) In a vertical milling machine, the head may be swivelled at an angle.

j) Milling machines are fitted with accessories like dividing heads, and ro• tary tables.

3. a) The use of multipoint cutting tools, enables the milling machine to achieve high cutting rates and also produce a good surface finish.

b) These machines are extremely versatile, and have three independent ta• ble movements, longitudinal, transverse, and vertical. They are used in workshops, but lack the stability required for heavy production work.

c) A horizontal milling machine has a horizontal spindle, which receives its power from a motor, through belts, gears, and clutches.

d) The spindle has a tapered hole, into which various cutting tools and ar• bors, can be inserted. The arbor is an extension of the machine spindle, and milling cutters can be mounted on it.

e) In the vertical milling machine, the spindle head is perpendicular to the work table. The spindle head can also be inclined at an angle, permitting the milling of angular surfaces. 180 Answers to exercises

Exercises XX

1. a) In the process of grinding, metal is removed from a metal surface, by a rotating abrasive wheel. b) Grinding produces high dimensional accuracy, and a good surface finish. c) Very little metal is removed from a surface by grinding. d) Grinding is the only method that can be used to machine materials, that are too hard to be machined by other methods. e) The different grinding methods available are, external and internal cy• lindrical grinding, surface grinding, and form grinding. f) In external cylindrical grinding, the workpiece is rotated about its own axis, while it moves lengthwise in contact with a revolving grinding wheel. g) In internal cylindrical grinding, the workpiece is rotated about its own axis, whilst the cylindrical grinding wheel rotates against the direction of rotation of the workpiece. h) Surface grinding may be done, by using the periphery, or the end face of the grinding wheel. i) Form grinding is used to accurately finish surfaces, that have already been machined to a special shape. j) Aluminium oxide grinding wheels are used to grind materials of high tensile strength.

2. a) Grinding is a finishing operation which gives high dimensional accuracy to workpieces. Answers to exercises 181

b) Very little metal is removed from the surface in a grinding operation. c) Surfaces which are too hard to be machined by other methods, can be machined by grinding. d) External cylindrical grinding is used to produce cylindrical or tapered surfaces. e) Internal cylindrical grinding is used to produce cylindrical holes, or internal tapers, on a workpiece. f) In surface grinding, the periphery or the end face of the grinding wheel maybe used. g) Form grinding is done with specially shaped grinding wheels to accu• rately grind surfaces which have already been machined. h) In the centreless grinding method, the workpieces are not held and ro• tated between centres. i) Aluminium oxide wheels are better suited for grinding materials of high tensile strength. j) The abrasives used in grinding wheels are small grains of silicon carbide or aluminium oxide.

3. a) Grinding is an operation which is done using a rotating grinding wheel, and which removes metal from the surface of a workpiece. b) Grinding is normally a finishing process, which gives high dimensional accuracy, and a good surface finish, to workpieces which have been ma• chined by other methods. c) Materials which are too hard to be machined by other methods, can be machined by grinding. Only a small amount of metal is removed in a grinding operation. d) External cylindrical grinding is used to produce a cylindrical or tapered surface, on the outside of a workpiece. The surface grinding process is used to generate flat surfaces, using the end face, or the periphery of the grinding wheel. 182 Answers to exercises

e) The abrasives used in grinding wheels, are small grains of silicon car• bide or aluminium oxide. Grinding wheels are made by using a suitable material to bond the abrasive particles together. Answers to exercises 183

Exercises XXI

1. a) Automatic lathes are used for the production of a large number of identical components.

b) In the past, small batches of components were produced by the use of conventional machines, and skilled labour. c) The disadvantages of the previous methods of production, were the low machine utilization time, and the high cost of production.

d) In flexible automation, a machine produces components automatically, in accordance with predetermined instructions. Only the instructions need to be changed, when another component has to be manufactured.

e) CNC machines have electrical drives which are controlled by a com• puter, unlike ordinary machines which have drives controlled by a skilled operator. f) The machine utilization time is high, because the waiting time required for resetting the machine is small. g) When a new batch of components has to be produced, only a change in the computer program is necessary. h) The skill of the operator is unimportant, because the accuracy is only dependent on the accuracy of the machine and the program. i) Each tool is held in an adaptor and stored in a magazine. The required tool is selected from a magazine, and is used to replace the one already in the machine. j) Minimization of wear is achieved, by using rolling components, instead of sliding components.

2. a) Automatic lathes are used for the production of a large number of identical components. 184 Answers to exercises

b) A new development has been the use of numerically controlled ma• chines for small batch production.

c) Previously, small batch production was achieved using skilled labour, and conventional machine tools.

d) This resulted in a low machine utilization time, and a high cost of pro• duction.

e) The operation of a CNC machine is controlled by a computer program.

f) Special tooling, like jigs and fixtures, are not required when a CNC ma• chine is used.

g) Minimization of wear in CNC machines is achieved, by using rolling components, instead of sliding components.

h) Measuring instruments give a continuous indication of the position of the cutting tool. i) The correct tool for a particular operation is selected automatically from a magazine. j) The massive construction of the machines, gives them the stability needed, to withstand large cutting forces.

3. a) Single and multispindle automatic lathes have found their greatest application, where a large number of identical components have to be produced. A new development has been the use of computer controlled machines, for the production of small batches of components.

b) In the past, small and large batches were produced on conventional ma• chines, using highly skilled labour. This resulted in a low machine utili• zation time, a long waiting time, and high production costs.

c) The operation of a CNC machine tool is controlled by a computer. Ma• chine tools which are used in this type of work, do not have the normal movements and drives used by conventional machines.

d) CNC machines do not need to be set up by a highly skilled operator. Only a change in the computer program is necessary to produce a new Answers to exercises 185

batch of components. The flexibility of the system results in high ma• chine utilization times.

e) The machines are of massive construction. This gives them the stability needed to withstand large cutting forces, and the thermal effects caused by the large quantities of chips produced. 186 Answers to exercises

Exercises XXII

1. a) In an internal combustion engine, the fuel is burnt inside the engine, while in an external combustion engine, the fuel is burnt outside the en• gine.

b) The chemical energy of the fuel is converted into heat energy, and part of the heat energy is converted into mechanical energy by the engine. c) A petrol engine has four strokes.

d) The connecting rod and the crankshaft, have the function of changing the reciprocating motion of the piston, into the rotatory motion of the crankshaft.

e) The power stroke is the only stroke in which the engine extracts energy from the fuel.

t) The four strokes of the Otto cycle are called induction, compression, ig• nition, and exhaust.

g) In the induction stroke, the inlet valve opens, and the piston moves downward. This creates a partial vacuum, that sucks in the petrol-air mixture into the cylinder, through the open inlet valve.

h) The flywheel stores the energy generated during the power stroke, and uses this energy to move the crankshaft, connecting rod, and pistons, through the other three strokes.

i) The chief difference between the two engines, lies in the different meth• ods used for introducing fuel into the cylinder, and for burning fuel in the cylinder.

j) Multicylinder engines run more smoothly and silently, than single cylinder engines.

2. a) In an internal combustion engine, the fuel is burnt inside the engine. Answt

b) The chemical energy of the fuel is converted into heat energy, and part of this energy is converted into mechanical energy by the engine.

c) The valves can be opened or closed, to allow a petrol-air mixture to en• ter or leave the cylinder.

d) The connecting rod and the crankshaft enable the reciprocating motion of the piston to be converted into rotatory motion.

e) During the power stroke, the engine extracts energy from the fuel.

f) During the induction stroke, the inlet valve opens, and the piston moves downward.

g) During the compression stroke, both valves remain closed, and the pis• ton moves upwards, compressing the petrol-air mixture.

h) The sprocket wheel drives the camshaft through a chain drive.

i) The difference between a petrol and a diesel engine, lies in the different methods used for introducing and burning fuel in the cylinder.

j) Diesel engines have a higher thermal efficiency than petrol engines, and therefore consume less fuel.

3. a) The petrol engine and the diesel engine, are both combustion engines in which the fuel is burnt inside the engine.The chemical energy of the fuel is first converted into heat energy by combustion, and then into me• chanical energy by the engine.

b) Most petrol engines are based on the Otto four stroke principle, in which a mixture of petrol and air is first compressed, and then ignited.

c) The petrol engine has a cylinder with a tight fitting piston, which can undergo an up and down motion. In the head ofthe cylinder, there is an inlet and an outlet valve.These valves can be opened or closed to allow a petrol-air mixture, to enter or leave the cylinder.

d) In a four stroke process, the movement of the piston takes place in four stages, two upwards, and two downwards. These four strokes are called 188 Answers to exercises

induction, compression, ignition, and exhaust. Energy is extracted from the fuel, only during the ignition stroke. e) The petrol engine and the diesel engine are similar, as far as their me• chanical components are concerned. The main difference between the engines, lies in the methods used for introducing the fuel into the engine, and for burning the fuel. 189

Vocabulary

ability Fiihigkeit f angular winkelfbead Bordeln, Falzen v aim richten v bearing Lagern aircraft fuselage Flugzeugrumpf m bed Bett n alignment Ausrichtungf belt Riemenm allowance Spieln bend Biegen v alloy Legierungf bevel gear Kegelrad n although obwohl cj bilateral zweiseitig adj amongst unter pr billet Knilppelm angle Winkelm blacksmith Schmiedm 190 Vocabulary

blow Schlagm coke Koksm bolt Schraubef column Siiulef braze hartloten v combustion Verbrennungj briefly kurzadv commonly gewohnlich adj

brittle sprod~:; adj compare vergleichen v bum verbrennen v compensate kompensieren v bush Lagerbuchse f completely vollstiindig adv camshaft Nockenwellef complex komplexadj capable flihig adj component Bestandteil m carbon steel Kohlenstoffstahl m composed of zusammengesetzt aus v carburettor Vergaserm composite zusammengesetzt adj carriage Werkzeugschlitten m compound Verbindungf case harden einsatzhiirten v compress zusammendriicken v cast iron GuBeisenn concerned betroffen adj casting GuBm condition Voraussetzungj cause verursachen v cone Kegelm chain Kettef conical kegelfclamp Klemme/ conversion Umsetungf clean reinigen v convert umwandeln v clearance Spielraum m, Spiel n coolant Kiihlschmiermittel n clearance angle Freiwinkel m copper Kupfern clockwise im Uhrzeigersinn corresponding entsprechend adj clutch Kupplungf corrosive korrodierend, iitzbar adj coating Schichtf cost-effective kostengiinstig adj Vocabulary 191 counterbore Zylindrische Senkungf difficult schweradj countersink Kegel Senkungf dimension MaBn countersunk screw Senkschraube f direction Richtungf coupling Kupplungf discuss besprechen v crank Kurbelf disintegration Aufspaltungf crankshaft Kurbelwellef distance Entfemungf create erzeugen v dividing head Universal Teilkopf m cross member Quertriiger m dowel pin Diibelm cross rail Querschiene f drawing technische Zeichnungf crumble kriimeln v drift Austreiber m crystal grain Mikrokristall n drill Bohrerm cut schneiden v drilling bohren v cutting schneidend, scharf adj, drive treiben v Schneidenn drop forging Gesenkschmieden n cylinder Zylinderm drum Trommelf eylinderblock Zylinderblock m ductile duktil, dehnbar adj damage schaden v economical sparsamadj definite bestimmt adj efficiency Leistungsflihigkeitf depend abhiingen v efficient leistungsflihig adj depth Tiefej electrochemical elektrochemischer Vor- description Beschreibung f process gangm design entwerfen v electrolyte Elektrolyt n determine bestimmen,entschei- eliminate aussondem, ausschei- den v den v development Entwicklungf enable ermoglichen v deviation Abweichungf encounter begegnen v device Geriit n energy Energief dial gauge MeBuhrf engine Motorm die Schneideisen n engine head Zylinderkopf m die casting SpritzguBm enormous enorm adj difference Unterschied m ensure sichem, sicherstellen v 192 Vocabulary

equipment Ausriistung, Einrich- fon:e into einpressen, hineintrei- tungf benv essential wesentlich adj form Fonnj estimation Schlitzungj formed tool ProfilmeiBel m exaetly genauadj fourway toolpost Vierfachhalter m example Beispieln freely zwanglos adv excessive iibermliBig adj friction Reibungf exist existieren v fuel pump Benzinpumpef experience Erfahrungf fundamental grundlegend adj extensive umfassend adj galvanic action galvanischer Vorgang m extent AusmaB n, GroBef gasket Dichtungj external liuBerlich adj gearwheel Zahnradn extract ausscheiden v generate erzeugen v extremely sehradj glass fibre Glasfaserj fast schnell adj granule Granulatn fasten befestigen v grease Fettn feature Eigenschaftj grind schleifen v ferrous eisenhaltig adj grip greifen v filler Fiiller m groove Nutj finished component Fertigteil n, Fertigwaref guideways Bettfiihrungen pi finishing operation Endverfahren n guillotine Guillotine f fiXture Vorrichtung n, feste half (pl. halves) Hlilftej Anlagef hardness Hlirtef flanging bOrdeln v hardwearing widerstandsflihig adj flat flach adj headstock Spindelstock m flexible beweglich adj heat Hitze, Wlirme f fluid Fliissigkeitj heavy schweradj Oute Spannutf helical gears Zahnrlider mit flux FluBmittel n Schrligverzahnung n flywheel Schwungrad n hexagonal sechseckig adj hollow hohladj Vocabulary 193 identical identisch adj knowledge Kenntnis f, Wissen n ignite entziinden v lack mangeln, fehlen v immerse tauchen v lathe Drehmaschine f important wichtigadj lead Blein impossible unmoglich adj Ieadscrew Leitspindel f improve verbessem v linear linear adj inclined face schiefe Ebene f lubrication Schmieren n increase zunehmen v machining allowance Bearbeitungszugabe f independent unabhiingig adj machining centre Bearbeitungszentrum n indication Anzeigef maintain erhalten v induction Einfiihrungf maintenance Instandhaltungf inhibitor Inhibitor m major diameter Nenndurchmesser m inspect priifen v manufacture Herstellungf instruction Befehl m mass produce serienmiiBig herstellen v interchangeable auswechselbar adj massive massiv adj interfere iiberlagem v match anpassen v interlock ineinandergreifen v material Stoffm internal innerlich adj measurement Messungf introduce einfiihren v mechanism Mechanismus m involve verwickeln v mention erwiihnen v iron Eisenn metal chips Metallspiine m iron ore Eisenerzn method Methode/ irregular unregelmiiBig adj micrometer MeBschraube f jennying machine Kantenbearbeitungsma- mild steel Baustahl m schinef milling machine Friismaschine f jig feste Anlage, Vorrich- minimum Minimumn tung/ minor diameter Kemdurchmesser m v join verbinden mixture Mischungf joint Verbindungf molten metal fliissiges Metall n key Keilm motion Bewegungf keyway Nutf mould GieBforrnf knee Konsolef, Knie n 194 Vocabulary

movement Bewegungf permanent dauemdadj multipoint cutting Werkzeug mit mehreren permit erlauben v tool Schneidenn petrol Benzinn multipurpose mehrzweck- adj pinion Ritzeln necessary notwendig adj pipe Rohrn nitrocellulose Nitrocellulose f pitch of a screw Steigungf noise Geriiusch n planer Hobelmaschine f nominal dimension NennmaBn plant Anlage/ normalize normalgliihen v pliers Zangef nozzle Diisef polish polieren v numerical control Numerische Steuerungf polluting medium verschmutzendes Medi- numerous zahlreich adj umn nut Mutter/ polycrystalline vielkristallin adj object Gegenstand m popular beliebt adj

offset screwdriver Winkelschrauben- pour gieBen v zieherm power Kraft/ often oft adj practice ausfiihren v operation Verfahrenn practice Gewohnheit f orientation Orientierungf precise genauadj outlet valve AuBlaBventil n precisely priizise adv overhanging arm Gegenhalter m precision Genauigkeit f overlap iibergreifen v predetermine vorherbestimmen v oxy-acetylene Acetylen-Sauerstoff m predictable voraussagbar adj paint Farbef press Pressef part Teiln press pressen v particularly besonders adj pressure Druckm pasty teigig adj previous vorheradj pattern Mustern primarily hauptsiichlich adv penetrate durchdringen v probably wahrscheinlich perform leisten v process Vorgangm periphery Randm produce herstellen v Vocabulary 195 production Herstellungf repair reparieren v profile Profil n repeat wiederholen v projection vorspringender Teil m replace ersetzen v prototype Mustern require erfordem v punch Stanzwerkzeug n reservoir Reservoir n purpose Zweckm resin Harzn push schieben v resistance Widerstand m quantity GrllBef return zuriickkehren v quench abschrecken v revolution Umdrehungf quiet ruhigadj revolving sich drehend adj rack Zahnstange f ridge .Kammm rack and pinion Zahnstangengetriebe n rigidity Stabilitlit j radial radial adj rivet Nietef rake angle Spanwinkel m rod Rundstabm range Reihe j. Bereich m roUer Walze, Rollef rapid schnell adj rotary table Maschinenschraubstock, rate Rate/. MaBn urn 360° drehbar m ratio Verhliltnisn rotatory drehbeweglich adj reamer Reibahlef rough raub adj. reaming reiben v rub reiben v reciprocating pendelnde Bewegungf mst Rostm motion sandcasting SandguBm recirculating umlaufend adj screw Schraubef recondition iiberholen v screw thread Gewinden reduce vermindem, reduzieren securely sicheradv v select auswiihlen v regulate regeln v self-centering chuck Dreibackenfutter n reinforced concrete Eisenbeton m semi-skiUed angelemt adj reject ausscheiden v sequence Reihenfolgef relieve entlasten, entspannen v serve dienen v remarkable bemerkenswert adj set screw Stellschraube f remove abtrennen v 196 Vocabulary setting-up Einstellungf stability Stabilitiit f severe streng adj stage Phase/ shape Form/ standard Norm/ shaper StoBmaschine f steel Stahlm shaping machine Hobelmaschine f strand Strangm shear scheren v strength Starke, Stabilitiit/ shears (snips) Scheref stress Spannung,Beanspru- sheet Blechn chungf ship's hull Schiffsrumpf m strict streng adj shock Sto6m strip abziehen v sideways seitwarts adv stroke Hubm similar iihnlich adj structure Strukturf single point tool SchneidmeiBel m stud Stiftschraube f size GroBe/ sturdy stark adj skill Geschicklichkeitf successively hintereinander adv sleeve Muffe/ sufficient genug, ausreichend adj sliding gleitend adj suitable geeignet adj slot Schlitzm support Tragerm smooth zUgigadj surface finish Oberflachenqualitat f socket spanner SteckschlUssel m swivel drehen v solder loten v tailstock Reitstock m spanner SchraubenschlUssel m take apart zerlegen, auseinander- nehmen v spark plug ZUndkerzef tang Kegellappen m specification Spezifizierungf tap Gewindebohrer m spelt Messinghartlot n tap hole AbfluBloch n spindle Spindel/ taper VerjUngung/ spiral Spiralef taper shank Kegelschaft m spline lange Nut/ temper anlassen v spring washer Unterlegscheibe f temporary vorUbergehend adj sprocket Kettenrad n tensile strength Zugfestigkeit f spur gear Stirnrad n thread Gewindegang m Vocabulary 197 tight dichtadj usually gewohnlich adv tighten festziehen v utilization Nutzungf time Zeit/ vacuum Vakuumn tip Spitzef vanadium Vanadiumn tolerance Toleranzf vapour Dampfm tool head Werkzeugschlitten m variation Veriinderung f tool post MeiBelhalter m vernier caliper MeBschieber m topic Theman versatile vielseitig adj tough widerstandsfahig adj vibration Schwingung, Vibration/ toughen ziih machen v vice Schraubstock m transition Ubergangm water-tight wasserfest adj trepanning schiidelbohren v wedge Keilm tungsten Wolframn welding SchweiBenn turn drehen v wiring Drahteinlegen n turning centre CNC Drehmaschine f work-harden kalthiirten v type Sortef worm gear Schneckengetriebe n unilateral einseitig adj worthwhile lohnendadj unite vereinigen v wrought iron SchweiBstahl m useful niitzlich adj 198

Index

A ball bearings 60 abrasion 16 handsaw 15 abrasion marks 16 beading 15 abrasive particles 118 bearing support 111 abrasive wheel 117 bearings 60 accessories 99, 112 bending 15 accurate 8, 43, 122, 123 bending rollers 15 accurately 81 bevel gear 67, 112 acid paste 25 bilateral tolerance 94 adaptor 124 billet 51 alignment 51 blowpipe 26 allowance 38, 94 blows 57 alloys 33,39 body 82 aluminium 33 bolts 20 aluminium oxide 118 bond 25, 118 angle blocks 7 bonding materials 118 angular surface 112 borax 25 annealing 44 boring 81 anticlockwise 60 brass 33, 118 arbor Ill brazed joint 25 assembly 7 brazing 25 automatic lathe 122 brittle 50, 89 automatic presses 15 brittleness 43, 56 automatic production 122 bronze 60 automation I automobile engine 60 c automobile gear box 67 camshaft 129 axis 60 capstan 99 carbide tipped tools 89 B carbon steel 33, 56 back-up wheel 117 carbon-rich substance 56 backlash 124 carburettor 39 , 130 Index 199 carriage 99 counecting rod 50, 128 case hardening 56 contoured surface 105 cast iron 20, 33, 118 conventional machine tools 122 casting 20 corrosion 16 cavity 51 corrosive action 25 centre drill 81 cost of manufacture 95 centre punch 1, 81 cost of production 122 centreless grinding 117 counterbore 81, 82 centres 75 countersink 81 ceramics 118 countersunk heads 20 chain 61 coupling 61,99 chemical energy 128 crank 61 cherry-red 56 crankshaft 50, 61, 128 chips 123 cross-sectional area 51 chisel 2, 56 crystals 43 chuck 99 cutting 15 clamp 7, 82 cutting angles 88 clamping device 20 cutting edge 56 clearance angle 2, 88 cutting fluid 88 clearance fit 94 cutting forces 123 clockwise 60 cutting stroke 105 CNC 122 cutting tools 33 cold rolling 43 cycle 129 column 111 cylinder 60, 67 combustion process 129 cylinder block 20 complex forms 33 cylinder head 20 components 20, 44, 50, 74 cylindrical hole 117 composite materials 34 cylindrical surface 99 compound table 81 compress 128 D compressed mixture 129 damage 16 compression stroke 129 depth of engagement 74 computer 1, 122 deviation 94 computer program 123 devices 7 computerized numerical control 122 diameter 74 cone 67 die 2, 15, 75 conical surface 67,99 diecasting 3 8 200 Index

diesel engine 128, 130 finished component 43, 94 dimensional accuracy 94, 117 fmishing operation II 7 dimensions 7 fixtures 7 direction of the motion 67 flanging 15 dividing heads 112 flat surface 105, 117 double thread screw 74 flexibility 123 dowel pins 38, 95 flutes 82 drift punches 1 flux 25 drilling 81 flywheel 129 drilling machine 68 folded metal joints 15 drills 75 folding 15 drive 122 folding machines 15 drop forging 50 force 95 ductile 44, 50 forging 50 forging process 50 E form grinding 117 electric arc welding process 26 formed tools 105 electroplating 16 friction 60, 67 engine 20 fuel pump 39, 130 engine balance 129 engine block 33 G engine head 39 gas-air mixture 128 engineering materials 33 gas-tight 20 engineering production 94 gasket 20 estimation of costs 123 gearbox 67, 68 exhauststroke 129 gear tooth 50 external 67 gears, gear wheels 60, 67 external combustion engine 128 glass fibre 34 external cylindrical grinding 117 grain structure 4 3 external screw thread 74 gravity die casting 3 8 grease 25, 60 F grinding 81 , 11 7 fastening devices 20 grinding wheel 75, 117 feed movement I 00 groove 105 files 1 gudgeon pin 60 filler rod 26 guideways I 06 film 56 Index 201

H internal combustion engine 128 hacksaw internal cylindrical grinding 117 hammer 1 internal screw thread 74 hammered 50 internal taper 11 7 hand tools 1 iron 33 hard solder 25 irregular surface 105 hard soldering 25 harden 56 J hardness 43 jennying machines 15 head 82 joining 15 headstock 99 headstock spindle 99 K heat treatment 15, 43 keyway 105, 123 heavy-duty work 68 knee 111 helical gear 67 hexagonal form 20 L hexagonalkey 20 lacquering 16 hexagonal turret 100 lathe 88,99 high carbon steels 56 lead 74 high limit 94 leadscrew 99 high speed steels 33 limit 94 holding and clamping devices 7 linear motion 60, 68 hole 94 liquid form 33 horizontal 105 location 81 hydraulically 106 longitudinal 111 hydrochloric acid 25 low limit 94 lubricating properties 88 I lubrication 60 identical components 122 ignite 128 M inclined 105 machine 1, 60 inclined faces 74 machine beds 33 induction stroke 129 machine tool 38 inspection 94 machine utilization time 122 interchangeability of components 94 machining 50 interference fit 95 machining centre 123 internal 67 magazine 124 202 Index

maintenance 1, 99 noncorrosive flux 25 manufacturing industry 94 normalizing 44 manufacturing process 43 numerically controlled machines 122 marking-out equipment 7 nuts 20 massive 105 nuts and bolts 20 material 2 materials 33 0 measuring instruments 124 oil bath 67 mechanical components 130 orientation of the grains 43, 50 mechanical energy 61, 128 Otto four stroke cycle 128 mechanical hammers 50 outlet valve 128 mechanically I 06 over-hanging arm Ill metal alloy 25 oversize 82 metal billet 51 oxide 25,56 metal components 16 oxy-acetylene welding 26 metal fasteners 16 metal surface p metals 2, 33 parallel guideways 99 metric thread 75 pattern 38 mild steel 21, 33 performance 130 milling cutters 112 periphery 117 milling machine Ill petrol engine 128 minimization of wear 123 pin punch models I pinion 67 molten metal 38 piston 60, 128 morse taper 75 pitch 74 motion 60 plain bearing 60 motor car engine 20 planer 105 mould 33,38 plastics 33 movement 81, 122 polishing 16 multicylinder engines 129 polycrystalline materials 43 multipoint cutting tool Ill power stroke 128 multispindle 122 precise 81 predetermined program 122 N pressure 95, 129 nails pressure die casting 3 8 nominal dimensions 94 production work 99, Ill Index 203 prototypes 1 scraper 1 pulleys 60 screw thread 20, 74 punch 1, 15 screwdriver push fit 95 screws 74 screwthread 2 Q self-centering chuck 82 quality of the fit 94 set screws 20 quenched 56 shaft 60 quick return mechanism 1OS shank 82 quieter 67 shape 43 shaper 105 R shaping machine 88 rack and pinion 61, 68 shears 15 rake angle 2, 88 sheet metal 1, 15 ratio 68 silicon carbide 118 reamer 75, 81 silver solder 25 reciprocating motion 60 single point cutting tool 99, 111 reconditioning 20 single thread screw 74 red hot metal 50 skilled labour 122 regulated 100 skilled operator 100 regulating wheel 118 sleeve 82 rejected components 95 sliding components 123 resin 25, 34 slot 105 resistance welding method 26 small batches of components 122 return stroke 1OS small end 60 revolution 129 smoother operation 67, 129 rigid bed 99 socketspanner 51 rigidity 106 solder 15, 25 rivets and riveting 20 soldering 16, 25 roller bearings 60 spanner 1, 50 rolling components 123 spark plug 130 rotary tables 112 special tooling 123 rotatory motion 60, 68 specific type of work 74 specification 7 4 s speed 67 safety IS speed reducers 68 sandcasting 38 spelt 25 204 Index spindle 111 tolerance 94 spiral 74 tool changing 99, 123 splines 105 tool post 99 split shell bearings 60 tool setting 99, 100 sprocket wheel 61, 129 tool wear 88 spur gear 67 toothed wheel 67 stability 123 toughen 56 state of stress 43 toughness 56 steam engine 128 transition fit 95 steel 33 transverse 111 stiffuess 15 trepanning 81 stops 100 tungsten carbide 33 straight shank 82 turning centre 123 strength 15,33,43 turret 99 stress 15 twist drill 82, 112 stress relieving 44 stretching 15 u studs 20 unilateral tolerance 94 supports 60 upset forging 51 surface fmish 88, Ill surface grinding 117 v swivel 112 vee-blocks 7 versatile machine 112 T vertical 105, Ill T-slot 123 vertical milling attachments 112 tailstock 99 vice 7 tang 82 tap 2, 75 w taper 75,99 water soluble oil 88 taper shank 7 5, 82, Ill water-tight 15, 20 tapered surface 11 7 wear 67 tapping 81 wedge 88 tempering 56 welding 7, 16,25 tensile strength 20 white metal 60 thermal efficiency 130 wiring 15 thermoplastics 34 work rest 118 thermosetting plastics 34 work-harden 43 Index 205 workshop 7 workshop bench 7 workshop equipment 7 worm, worm gear 68 wrench 1 wrought iron 33, 118 z zinc chloride 25 Einfiihrung in die Umwelttechnik

Herausgegeben von Bertram Philipp.

1993. X, 286 Seiten mit 37 Abbildungen. Kartoniert. ISBN 3-528-04777-1

Dieses Buch wendet sich an [ __:____] fPRIDPP (HRSGf) _ :==J Studenten ingenieurwissen• [ ----~ schaftlicher Facher, die sich ~NDIE _ 4 tor Fragen des Umweltschut• IUMWEU IECHN~i( ] zes interessieren und an L angehende ,Umweltberater". Es fuhrt in die technischen Grundlagen ein und vermit• telt auch Grundkenntnisse des Umweltrechts und okolo• -~~---~- l gisch-wirtschaftliche Zusam• menhange.

Verlag Vieweg · Postfach 58 29 · 65048 Wiesbaden