PART TWO: POWER AND ENGINEERING 412 instruments but the method was first used for production in 1835 by Joseph Whitworth, using a worm cutter as a ‘hob’ to make spiral gears. Several other patents were obtained for hobbing machines but the first fully geared example to be used was that made by George B.Grant, c. 1887. By the end of the nineteenth century the general machine tools were established in their operating principles and many refinements had been made in machine spindle and carriage drives by gearing systems such as the gearbox invented in 1891 by W.P.Norton and incorporated in Hendey-Norton lathes. The features of interchangeable manufacture were well known and the mass production machinery ready for the explosion in manufacturing which was to take place in the twentieth century with the proliferation of the motor car and aeroplane. TWENTIETH-CENTURY ORGANIZATION OF PRODUCTION The key to further expansion lay in increasing the speed of cutting by machine tools and in organizing production to balance the machining and assembly of components so as to achieve the maximum rate of production of the completed product. Frederick W.Taylor was influential in both aspects. He carried out experiments on the shape, cutting angles, lubrication and materials of cutting tools to establish optimum efficiency and made dramatic improvements in output and tool life, culminating in his development of High Speed Steel containing tungsten. He demonstrated it at the Paris Exhibition of 1900, cutting mild steel at 36.5m (120 feet) per minute with the cutting tool red hot, and this revelation was so fundamental that all types of machine tool were to need redesign to increase rigidity, speed range and power to take advantage of the new tool material. The introduction of Stellite, a chromium, cobalt, tungsten alloy, in 1917, carbides by Krupps of Essen in 1926, and ceramic tools were to have similar effects later. A comparison of cutting speeds possible with these tool materials for grey cast iron shows: HSS 22.8m (75ft)/min.; Stellite 45.7m (150ft)/min.; carbide 122m (400ft)/min.; ceramic 183m (600ft)/min. Taylor also introduced a systematic examination of all parts of the manufacturing process through time study of each operation and the application of piece-rate bonus schemes which became known as the Taylor System of Scientific Management and established the principles of workshop management on production lines. The first four-stroke gas engine was started by Otto in 1862 and his liquid fuelled engine with electric ignition in 1885, at about the same time as Karl Benz used his engine for the first motor in 1886 (see p. 306ff). Besides the engine the motor car presented many problems in its manufacture. The need for a light but rigid chassis, and the design of suspension, steering and ENGINEERING AND PRODUCTION 413 transmission were initially solved in a crude way but were rapidly refined in two main streams of development, the European ‘bespoke’ type, represented first of all by the Mercedes of 1901 and later by the Rolls Royce Silver Ghost, and the ‘motoring for all’ concept in the USA exemplified by the Model T Ford. The former was produced by machine tools and methods which would be regarded as archaic by American standards, the latter with the benefit of much experience in interchangeability and ‘scientific management’. Britain’s motor industry was established around 1894 in Coventry and Birmingham, where cycle, sewing machine and textile manufacturers already existed with one major machine-tool maker serving these industries. With the coming of the motor industry this firm grew to become one of the most famous machine tool manufacturers in the world, Alfred Herbert Ltd. Frederick Lanchester was the first British producer of a motor car by interchangeable methods and designed machines, methods, jigs and tools for the purpose. One of his most important machine tools was the worm hobbing machine of 1896, and he also developed hardened steel roller bearings ground to a tolerance of 0.0002in (0.0051mm) for use in his gear box and back axle. In his system of gauges he adopted the unilateral system of tolerancing in preference to the American system of bilateral dimensioning, which allows variation above and below the nominal size. Production grinding as a precision operation was established in locomotive work, but was even more essential to the automobile industry. The crankshaft journal grinding machine produced by Charles Norton in 1903, the camshaft grinding machine by Norton and Landis of 1911, the planetary grinding machine for internal bores made by James Heald in 1905 and the piston ring face machine, also by Heald in 1904, enabled engine production to meet the rapidly growing demand for cars propelled by the internal combustion engine. At the London Motor Show of 1905, 434 types of car, British and imported, were available and between 1904 and 1914, UK car registrations rose from 7430 to 26,238. The early American car builders, White, Cadillac and Olds, initially built their cars one at a time, but when Ransome E.Olds moved to Detroit in 1899 he introduced the assembly line and used components manufactured elsewhere by subcontract. Engines from Leland and Faulconer and transmissions from Dodge were used to make the Merry Oldsmobile at the rate of 5000 cars per year in 1904. But it was Henry Ford in 1913 who made the production line move. His ‘Tin Lizzie’, the 1909 Model T, was mechanically simple, durable and cheap at less than $600, because this was the only way to achieve the output required. Using a rope and windlass, the chassis was pulled along the 250ft (76m) line and parts added to the chassis at assembly stages. The 12 1/2 hours at first required was reduced to 1 1/2 hours for the complete assembly. Standardization of models and component parts was a feature of the production organization, which by 1916 had raised output to 535,000 cars. By PART TWO: POWER AND ENGINEERING 414 1920, Ford was building half the cars in the world, and fifteen million Model Ts were made before the line was discontinued in 1927. Many other motor manufacturers were to emulate Ford, but the large investment in plant required caused bankruptcies. Such high-volume production posed new problems for machining in making parts in sufficient quantities to match 1 1/2-hour assembly times and machine shops grew and subcontractors prospered. E.P.Bullard was one machine-tool maker who met this challenge with his Mult- A-Matic vertical turret lathe, which machined flywheels in one minute. The Cincinnati Milling Machine Co. produced a version of Heim’s centreless grinder, patented in 1915, using a regulating wheel and narrow work rest with slanted top in 1922; the design of Han Reynold in 1906 for a centreless grinder was used in the French & Stephenson machine in England. With these machines valve stems were finish ground at 350 per hour and by 1935 the Cincinnati Co. had introduced the cam type regulating wheel to through grind parts fed from a magazine for gudgeon pins, king pins etc. Between the wars other machine tools were improved to take advantage of various new processes such as gear hardening, which required precision gear grinding machines using formed wheels, or shaving, using a helical cutter with serrated teeth. The broaching machine, patented by John La Pointe in 1898, became a vital machine in workshops to produce, in one pass, bores or flat surfaces by the progressive cutting action of increasing sizes of successive teeth. His pull broach was manufactured in 1902 and hydraulic power was employed in 1921 by the Oilgear Company machine. The early twentieth century also saw the introduction of the individual electric motor drive for machines which was eventually to eliminate the ‘forest of belts’ typical of all early production factories. An event of considerable consequence for metrology and the improvement of workshop accuracy and inspection was the development by Carl Edward Johansson in Sweden of precision gauge blocks to be used in calibrating bench gauges. These were made in a set of 52 to give, in combination, any division between 1 and 201 mm. He fixed the temperature at 20°C for the standard sizes and a face width of the gauges at 9mm for the proper and most accurate use of the blocks. The system was patented in England in 1901 and brought with it many accessories which could be used in conjunction with the blocks to provide a whole system of gauges of high accuracy. This reduced the need for skilled men to carry out measurements using micrometers by enabling operators quickly to judge the accuracy of their own work. ‘Go’ and ‘No Go’ gauges had been used earlier, but Johansson was the first to introduce adjustable anvils in a cast-iron frame with both ‘Go’ and ‘No Go’ gaps set in one inspection instrument with the accuracy of his gauge blocks, or slip gauges as they became called. To check a diameter the operator tried the gauge which should pass the ‘Go’ anvil but not pass the ‘No Go’ end. The difference in the anvil dimensions is the tolerance allowed on the dimension to which the part ENGINEERING AND PRODUCTION 415 may be made. Angle gauges, plug gauges and micrometers were also produced, and the blocks were used in setting up sine bars and as checks on parts using comparators. W.E. Hoke in the USA made gauges with a similar purpose in about 1920. Johansson’s gauge blocks became the dimensional standards for the whole world by 1926 and he is referred to as the ‘Master of Measurement’. The use of gap gauges also became common for the inspection of screw threads based on the idea of William Taylor patented in 1905 which specified the ‘Go’ end as full thread form but had ‘No Go’ gauge ends to check specific elements such as the core diameter. Taylor was also interested in measuring surface roughness, but it was Richard Reason of Taylor, Taylor & Hobson who in 1937 produced the first Talysurf which used electrical amplification of the movement of a stylus over the surface being tested to give a measure of its roughness. The two most significant general purpose production machine tools of the first half of the twentieth century were the heavy production grinding machine by Norton in 1900 and the Bridgeport turret milling machine. The former was designed with the size and power to plunge grind cylindrical parts using wide wheels to eliminate finish turning in the lathe, and its crankshaft version of 1905 revolutionized the engine industry. The Bridgeport machine consists of a multi-purpose head for drilling and milling with its built-in motor drive mounted on an arm which can be swung over the work table. This machine was originally produced by Bannow & Wahlstron in 1938 and has been the most ubiquitous machine tool since. In 1921 the machine which was to have the greatest impact in the toolroom was produced by the Société Genevoise of Switzerland. The jig borer (Figure 7.10) was developed from the pointing machine of 1912 used in the watchmaking industry for accurately locating holes in watch plates. Scaled up to engineering standards, it gave 0.0001in (0.00254mm) standard in locating holes and was invaluable in the manufacture of the gauges and jigs increasingly called for in the mass production industries where tasks were being made shorter and less skilled. The Hydroptic machine, with hydraulic work table and optical scale, was introduced in 1934. To further maintain this level of accuracy after heat treatment, the jig grinder was developed in the USA by Richard F.Moore in 1940. Another Swiss machine tool which continues to be of importance is the type of automatic lathe also born in the watch industry, introduced by Schweizer in 1872, but now widely used in many industries. It has a quite different operating action in its moving headstock which provides the feed of the work into various tools, giving a more versatile and higher operational speed than the American auto. The general purpose centre and turret lathes continued to be improved to give greater accuracy and flexibility of operation and by the late 1920s had hardened and ground beds, thrust bearings using balls and rollers and special turret tools, such as the self-opening diehead of 1902 made PART TWO: POWER AND ENGINEERING 416 Figure 7.10: The jig borer, produced by the Société Genevoise of Switzerland in 1921. ENGINEERING AND PRODUCTION 417 by Vernon, and the collapsing tap devised by C.M.Lloyd in 1916. Major improvements were made in spindle speed capacity and rigidity to match the continued increase in capability of cutting tool material. Many types were produced from the tungsten carbide of 1926 to the tungsten, titanium carbide developed in 1938 by P.M. McKenna. They were all very brittle, and cutting tools were made with steel shanks and tips of carbide brazed to them. Modern tools use specially designed tips to be carried in a holder fitted to the tool shank. In 1914–15, Guest in England and Alder in the USA had devised systems of selecting grinding wheels in terms of grit, grade and bond, but the carbide tools were too hard to be ground by ordinary abrasive wheels and it was the Norton company which produced a small diamond bonded wheel capable of dealing with them in 1934. To obtain rapid, accurate speed control the infinitely variable gear drive patented by G.J.Abbott of London in 1924, using a link chain to engage an expanding or contracting ‘V’ pulley, became widely adopted to provide stepless speed changes. The pre-selector gear box was patented by F.A.Schell in Germany in 1929 and Alfred Herbert & Lloyd of Coventry in 1932, and Alfred Herbert used it in their Preoptive headstock from 1934. Increasing accuracy of machining called for an equally accurate measuring device in the hands of skilled machinists, and the early screw calliper invented by Jean Laurent Palmer in 1848 was developed by Brown & Sharpe with enclosed screw and named the Micrometer calliper in 1877. Ciceri Smith of Edinburgh invented a direct reading micrometer in 1893 and Brown & Sharpe produced their version of this in 1928. Johansson of Sweden and Carl Zeiss of Germany made micrometers in 1916 and 1918 respectively. Moore & Wright were the first English company to make this instrument, which became the symbol of the skilled craftsman; their micrometer of 1930 employed a new thread grinder made by the Coventry Gauge and Tool Co. using a diamond cut ribbed wheel which gave a pitch accuracy within 0.0001in (0.00254mm), the best in the world at this time. In the high-volume flowline production world of automobile manufacture the trend was to incorporate machine tools into a conveyor-based transfer machine, each cutting station being designed to carry out appropriate operations on the faces of the workpiece presented to it by the location arrangement on the moving platen. Each station was designed to carry out its work in a similar time period. The first machine of this type was installed at the Morris Engine factory in 1923 and was 55m (181 feet) long with 53 operations. WELDING, ELECTRO-FORMING AND LASERS Joining metals by heat and filler was practised in bronze statuary c. 3000 BC and the first welded iron joint appears in a headrest from the tomb of PART TWO: POWER AND ENGINEERING 418 Tutankhamun, c. 1350 BC. The heat required to achieve local melting of iron and steel had to await the production of oxygen by Priestley in 1774, acetylene by Davy in 1800 and Linde’s method of extracting oxygen from liquid air in 1893 before the oxy-acetylene welding torch could be devised by Fouché and Picard in 1903 to give an adjustable flame of 3250°C. A patent for welding by electric arc, filed in 1849 by Staite and Auguste de Meitens, devised a method using carbon electrodes, but it is the use of the consumable bare steel rod by the Russian N.G. Slavianoff in 1888 which makes this device recognized as the beginning of metal arc welding. Considerable skill was required to strike and maintain the arc with a bare metal electrode, and coatings have been developed to improve arc stability and provide a protective layer for the weld. Kjellberg in 1907 introduced the first flux coating and in 1909 an asbestos yarn-covered electrode was used. Many different materials have been employed as coatings, including cellulose, mineral silicates and carbonates, to suit welding in different conditions. Manual metal arc is the most used welding process, but Elihu Thompson’s invention in 1886 of the use of electric power to achieve welded joints by resistance heating is very significant, as it took welding from the maintenance function into production. This butt-welding machine was the forerunner of the resistance spot welder between 1900 and 1905 and the seam welder. The submerged arc process, developed for the shipbuilding industry in the USA and USSR in the mid-1930s, employs a powder flux to completely cover the weld pool and the end of the electrode wire. It allows high welding current and low electrode usage in automatic processes. Gas shielding of the arc and weld metal from atmospheric contamination had also been considered from 1919 by Roberts and van Nuys and in the 1930s interest centred on the inert gases, but it was not until 1940 that the Northrop Aircraft Company experimented with tungsten electrodes and helium gas which was used successfully on thin gauge stainless steel. Further advances using other gases followed to give techniques able to cope with the welding of aluminium alloys and other difficult metals. With these developments electric welding became the key process in the rapid fabrication of locomotives, ships and automobiles (linked with the contour sawing of steel made possible by the band saw developed by Leighton A.Wilkie in 1933) and played a huge part in the wartime production effort required from 1939. During and after the Second World War many developments took place in standard electric welding processes such as submerged arc and inert gas tungsten arc welding. The latter has had the addition of an insulated water- cooled nozzle to form a chamber around the electrode to produce an arc plasma in the form of a flame when the arc is struck from the electrode to the nozzle. This is a non-transferred arc which is used for metal spraying with the addition of powdered metal to the plasma. If the arc is struck between the electrode and the work it is constricted in passing through the nozzle orifice ENGINEERING AND PRODUCTION 419 and this is the transferred arc used for cutting and welding. It is used at low currents for sheet metal and at about 400amp for welding thick metal using the keyhole technique. It requires an additional inert gas shield when used for welding. The inert gas metal arc process was introduced in 1948 and uses an electrode of metal which is consumed in the process as a filler. Many other gases have been used as shields, notably argon and CO 2 , and it is particularly useful and economic in welding aluminium using small-diameter wire and direct current with the electrode as positive. Friction welding, introduced in the Soviet Union in 1953, uses the heat developed by contrarotating parts held in contact at high speed until the temperature is high enough for welding when rotation is stopped and the ends forced together. A number of processes using electrical methods of forming workpieces have been devised which have proved useful in particular applications. Electrolytic machining of metals was introduced by Gusseff in 1930 employing the principles of electrolysis and shaped cathode, so that passage of an electrical current through a suitable electrolyte caused the anode to be eroded to match. The workpiece was placed at the anode. Chemical milling developed from the ideas of decorative etching produced by Niepce in 1822 and used by Richard Brooman in his patent of 1865 for forming tapered rods. The success of the process depends on the selection of etching chemicals and the inert materials used for masking. In 1936 Griswold in New York patented the technique which has been widely used in the production of printed circuit boards for electronic communications and control equipment. In 1953, M.C.Sanz led a team in the USA to develop the process for manufacturing parts used in aircraft structures and it was used in creating structural parts for the Space Laboratory and Apollo programme (see Chapter 13). In 1961 the process was used to photo-etch transistors on silicon chips. During the Second World War in 1943 electrical discharge machining, commonly called spark erosion was introduced principally to form cutting and shaping tools made of very hard alloys and carbides which were difficult to produce by any other methods. Modern machines give three-axis cutting by use of the travelling wire technique. Ultrasonic methods were first developed in 1935 by Sokolov to detect flaws in metal, and this technique has continued as a non-destructive way of checking welded joints. In 1957 the use of this level of oscillation about 20kc/s was used in drilling round and shaped holes, the reciprocating tool being fed with an abrasive slurry which does the actual cutting. The laser (Light Amplification by Stimulated Emission of Radiation) was invented in 1958 by Townes and Schawlow, although their priority has been disputed. Theodore H.Maiman made the first practical laser in 1960 using a cylindrical ruby crystal. The coherent light produced by the helium-neon laser is used in the interferometer for many applications where movement in very PART TWO: POWER AND ENGINEERING 420 small displacements is to be measured. The laser is also used in metrology as an alignment tool, the narrow beam being transmitted to a photo diode at the end of the surface being checked. At points along the surface being checked, a zone plate, equivalent to a weak lens, is positioned so that if any deviation is present the image on the photo diode will be changed and indicate misalignment. The laser has found many applications in such areas as eye surgery, holography, military range finders and sights, surveying and cutting and welding. A laser beam was used in 1962 to bore a hole in diamond as a demonstration of its power and is now used to make wire drawing dies. The first computer-controlled cloth cutter using a laser was employed by the clothing firm John Collier in 1974. High precision welding can be performed by laser and it completes joints very quickly, but is more difficult to focus and control than the electron beam. This technique, introduced in 1957 to weld nuclear fuel elements, can only be used in a vacuum, but has become increasingly important in making welded joints in micro-electronic devices and on the special alloy material used for jet engine turbine blades. In 1986, CO 2 lasers became available with 600–3000W power and these work on most metals, composites and plastics. Industrial machines with two laser beams to cut three-dimensional sections also exist. At the other end of the scale a laser micro-welder was designed and built by International Research and Development in 1974 to be used by hand in attaching such things as thermo- couples and strain gauges to research and production equipment. The ‘Diffracto gage’ laser strain measurement system accurate to 1–5µm was announced by the Canadian Company in 1973. WARTIME ADVANCES The Second World War was a greater trial of strength in terms of technology and materials than any previous conflict; as well as producing many inventions it accelerated the adoption of new ideas in manufacturing techniques and the organization of production. Because the work force had to grow tremendously it was essential to employ unskilled women on repetitive but precision work. Although they proved to be far more dextrous than men and able to keep up a higher and continuous rate of output on the sort of light capstan lathe operation involved in such areas as fuse work, and made some remarkable achievements in aircraft production and in unpleasant conditions such as welding, intensive training methods and simplified operations were needed. The principles of flow production and interchangeability were applied fully and the few skilled men available were used only to set up machines, maintain cutting tools, jigs and fixtures and, in some cases, operate statistical quality control. These control methods were designed on the basis of probability theory to ensure that all output was good by periodic measurement and recording of dimensions to ENGINEERING AND PRODUCTION 421 observe trends in accuracy and correct faults before scrap was produced. Considerable use was also made of ‘Go’ and ‘No Go’ gap gauges and large-scale displays to indicate satisfactory dimensions without measuring. Many different types of device were used, such as the Sigma comparator of 1939, which employed a mechanical movement in conjunction with electrical contacts to illuminate lights: red for scrap, green for pass and yellow for rectification. Fluid gauges using liquid, such as the Prestwich, and the air gauges designed in 1928 by Marcel Menneson of Solex in France were the basis of high magnification comparators made by Sigma and by Mercer in England and the Sheffield Corporation in the USA and used in almost every engineering factory. The English versions used pressure difference, as in the Solex, but the Sheffield product measured air flow as it was restricted by the component. All these comparators depended on their setting up in conjunction with a master gauge or component with the tolerance range shown by indicators. The simple rack and pinion dial gauge originally made by B.C.Ames in the USA in 1890 was primarily produced as competition for the micrometer of Brown & Sharpe and L.S.Starrett, although its measuring accuracy was not comparable with that of the screw micrometer. More precisely made dial gauges, conforming to the British Standard set in 1940 and used with slip gauges to set the dial, became important and cheap inspection instruments widely used to this day. In addition to the main production shop’s need for inspection instrumentation, the toolroom inspection department and metrology laboratory required accurate measuring machines and instruments to check gauges, jigs and fixtures and, as so many of these were manufactured in Germany by Zeiss, it was necessary for copies to be made by British firms. One vital instrument was the optical dividing head used for essential work in the aircraft and armament industries, and improved versions were made by Cooke, Troughton & Simms and George Watts in conjunction with the Coventry Gauge & Tool Co. by 1939. American industry supplied war materials to the French and British from 1939 on a payment basis, but the Lend Lease Act proposed by President Roosevelt and passed in 1941 produced a massive turn-round of their own manufacturing. All automobile production was stopped and car plants turned over to aircraft production in large new factory buildings. These were quickly erected, but the biggest problem was the need for machine tools to fill them. This was solved by two-shift working, 12 hours for six days then two days off, in the machine tool works and by 1942 targets were achieved so effectively that at the end of the war there were 300,000 surplus machine tools in the USA. Apart from the organizational success in achieving high- volume production, probably the most significant technological developments of wartime affecting machine-tool design were the extensive employment of servo-mechanisms in gun control and radar and electronics in communications and control. These were to be the basis of modern numerically controlled machine tools. . proliferation of the motor car and aeroplane. TWENTIETH-CENTURY ORGANIZATION OF PRODUCTION The key to further expansion lay in increasing the speed of cutting by machine tools and in organizing production. accurate to 1–5µm was announced by the Canadian Company in 1973. WARTIME ADVANCES The Second World War was a greater trial of strength in terms of technology and materials than any previous conflict;. examination of all parts of the manufacturing process through time study of each operation and the application of piece-rate bonus schemes which became known as the Taylor System of Scientific Management