An Encyclopedia of the History of Technology part 43 potx

PART TWO: POWER AND ENGINEERING 402 threads. His paper ‘On a uniform system of Screw Threads’, read to the Institution of Civil Engineers in 1841, was the beginning of rationalization in the manufacture of screwed fastenings. A compromise system was eventually worked out based on the average pitch and depth of thread in use by leading engineers, and a table was produced giving the pitches of screws of different Figure 7.8: A model of James Nasmyth’s original steam hammer of 1839. ENGINEERING AND PRODUCTION 403 diameters and a constant proportion between depth and pitch by adopting an angle of 55° for the ‘V’ profile. By 1858, Whitworth could claim that his standardization of screw threads had been implemented, although his advocated decimal scale was not accepted except where it coincided with fractional sizes and in Europe, where it competed with the metric thread. (A similar fate greeted his decimal Standard Wire Gauge which was never adopted as a national standard.) In 1853, Whitworth joined a Royal Commission visiting the New York Exhibition and reported that American machine tools were generally inferior to English, although their eagerness to use machinery whenever possible to replace manual labour appealed to him. A request by the Board of Ordnance to make machinery for manufacturing the Enfield rifle in 1854 turned his interest towards the manufacture of firearms. He produced his own rifle and later cannon which were superior to their competitors in performance but they were rejected by the official committees, although he obtained large orders from abroad. His visit to America also confirmed his belief in the value of technical education, first shown in his support for the Mechanics Institutes and Manchester School of Design in the late 1830s, and led to the launch of Whitworth Scholarships in 1868–9. Unfortunately he was a supreme egotist, which led to conflict with authority, and his rigorous, authoritarian control of the details of his manufactures stultified later development. The greatest users of machine tools of the day were the engine builders. Concurrently with Henry Maudslay’s, the works of Boulton and Watt at Soho, Birmingham, and Matthew Murray’s Round Foundry at Leeds expanded rapidly at the end of the eighteenth century. Such growth was only possible by the injection of capital and it was at this stage that the business men, Matthew Boulton at Soho and James Fenton at Leeds, began to make their impact on machine-tool building by financing the inventiveness of the engineers to take advantage of the great demand for engines and selling the tools developed for this purpose to other manufacturers. The Soho Foundry was completed in 1796 and William Murdock was put in charge in 1798. He constructed a massive horizontal boring mill of Wilkinson pattern, but with his own worm and wheel drive and an attachment to machine the end face of cylinders. A 64in (162.5cm) diameter cylinder was completely machined on this mill in 27 1/2 working days in 1800. A vertical boring mill was also built at Soho in 1854 to bore four cylinders for Brunel’s Great Eastern steamship to 7ft (2.13m) in diameter. This engine produced 2000hp and was the most powerful in the world at that time. Many tools were purchased from smaller makers for general purposes and William Buckle, who became manager at Soho in 1825, introduced the first large screw cutting lathe to the works: previously large screws had been cut by hand methods. Matthew Murray at Leeds was more inventive and a better production engineer, making work of higher quality than that of Soho, and was one of the first manufacturers of high quality PART TWO: POWER AND ENGINEERING 404 machine tools for sale in addition to engines. He devised the ‘D’ slide valve for steam engines and designed and built a planing machine to make it which was so ahead of its time that it was kept secret. Many designs of boring mill were produced by Murray and sold in Britain and abroad in which screw drive to the cutter head was incorporated by 1802. Murray’s steam locomotives were the first commercially successful in the world (see p. 559). Other machine tool designers had different primary objectives. One of the most outstanding was James Fox who gave up his post as butler to a country parson to make improved textile machinery. In order to do this he had first to design and construct his own machine tools and he was highly successful in this. His detailed improvements in carriage traverse became standard practice on the lathe. His first planing machine was built in 1814 and by 1817 it included power drive to the table with automatic reverse and automatic feed to horizontal and vertical tool travel. The machine tools built by Fox were ahead of other manufacturers in the detailed design of traverse mechanisms and precision guideways and he was a successful exporter to France, Germany, Russia and Poland. Several of his machines can be seen in the museum at Sielpia Wielka in Southern Poland. MASS PRODUCTION Special purpose machine tools are designed to perform a particular operation repetitively in the manufacture of numbers of specific products. Clockmaking was the first important application of these techniques and some of the machines developed had features used later in general purpose machines. Joseph Bramah’s lock, which he invented in 1784, required many small parts in the construction which would have been difficult and uneconomic to produce accurately by hand methods, so he engaged Maudslay, following his training at Woolwich Arsenal, to help in devising and constructing suitable machines. A sawing machine, (c. 1788), quick grip vice, milling cutters, drilling templates and a spring winding machine (1790), were made and still survive in the Science Museum, London. The last of these exhibits, a screw method of traversing the spring wire winding head, appeared later in the screw cutting lathe. Bramah’s other inventions included: hydraulic press, fire engine, beer pump, extruded lead pipe, water closet, fountain pen, banknote numbering machine, and a wood planing machine with hydraulic bearings and feed system (c. 1809). Maudslay’s experience in special machine construction was useful, and laid the foundation of his fortune, when he was selected to manufacture the Portsmouth block-making machines designed by Marc Isambard Brunel. Working models of these machines constructed by Maudslay (now in the Maritime Museum, Greenwich) were useful in persuading the Admiralty to set ENGINEERING AND PRODUCTION 405 up its own block-making factory. Maudslay constructed all the full-size machinery between 1802 and 1809. The plant consisted of 45 machines of 22 different kinds. When it came into full operation making three sizes of block in 1810, it was producing 100,000 blocks per annum and was the first large-scale plant employing machine tools for mass production. With these machines ten unskilled men could do the work of no skilled blockmakers. Apart from two large sawing machines, all the others were of metal and precise in operation to allow the assembly of component parts. They were used up to the mid- twentieth century and several are now exhibited in the Science Museum in London: Mortising, 1803; Block Shaping, 1804; Scoring, 1804; Coaking, 1804; Circular Saw, 1803. The manufacture of firearms, particularly small arms, was another area requiring a high rate of production with the special problem of producing many small precision parts which could be made to fit together easily. Traditional methods of hand production were slow; and weapons were made of individual, non-standard parts, so that if a component was lost or broken a replacement had to be specially made by a skilled gunsmith. Large numbers of infantry could be made ineffective in this way and governments became concerned about this weakness should long campaigns have to be waged. In 1811 the British army had 200,000 useless muskets awaiting lock repairs. A French gunsmith, Le Blanc, was the first to propose in 1785, a system of manufacturing in which the components of firearms should be made so accurately that all parts would be interchangeable and thus allow simple replacement when parts failed in action. The French government appointed several committees to examine this proposal and approved its development, but the political difficulties and revolution in France prevented its realization. Thomas Jefferson, the American Minister to France in 1785, saw the products of Le Blanc’s workshop and tested the parts of the musket lock for interchangeability, reporting its value to his government, but it was not until 1798 that a contract to manufacture arms for the Federal Government on these principles was given. Eli Whitney, the inventor of the cotton gin (see Chapter 17), was the first to be awarded a contract from the $800,000 voted by Congress for the purchase of cannon and small arms. He was to provide 1000 stands of arms for which a payment of $15,000 would be made, with continuing payment up to 10,000 stands of arms. Whitney was unable to achieve the targets set in the contract and it is doubtful if he employed new methods of machining the parts rather relying on the use of filing jigs and the ‘division of labour’ to produce the 4500 muskets delivered in September 1801. The US government armoury at Springfield was also producing firearms and employing new machinery and methods of assembly and work organization which enabled production to increase from 80 to 442 muskets per month in 1799. John Hall designed his rifle in 1811 to be made by interchangeable parts at Harpers Ferry Armoury by 1817 and he introduced PART TWO: POWER AND ENGINEERING 406 many new machines, a system of dimensioning from a single datum, and gauges at each stage of manufacture to ensure accuracy. He also used secondary and tertiary gauges to check the bench gauges. Other American manufacturers began using these methods, including pistols by Simeon North and Elisha K.Root’s arrangements for making Colt’s revolver. By 1815 all firearms made to United States government contract were required to be interchangeable with weapons made at the National Armouries and the system was proved in 1824 when 100 rifles from different armouries were brought together, disassembled and reassembled at random successfully. The ideas of Hall were developed by Root at the Colt Armoury at Hartford which contained 1400 machines and proved a tremendous success, its influence being spread by the outstanding engineers who worked there in similar fashion to those from Maudslay’s workshop in England. Two of these men, Francis Pratt and Amos Whitney, were to form the great engine company and became great exporters of machine tools for gunmaking as well as principal manufacturers of engine lathes. The company also supported the research and development by William Roper and George Bond of a line standard comparator employing a microscope with micrometer adjustment to calibrate their gauges. Another armoury of importance was the Robbins & Lawrence shop in Windsor, Vermont, run by Richard S.Lawrence, Frederick W.Howe and Henry D. Stone. In 1851 they sent a set of rifles to the Great Exhibition in London and demonstrated the ease with which parts could be interchanged, creating the official interest which led to the Commission to America which was chaired by Nasmyth and had Whitworth as one of its members (see p. 403). Their successful visit and recommendations led to the order for Robbins & Lawrence and the Ames Manufacturing Company to supply similar machinery for the Enfield factory to manufacture the 1853 pattern rifle musket, thus bringing the American System to England. In addition to the machinery several skilled men from the American armouries were imported, notably James Henry Burton who became chief engineer at Enfield. After serving his five year contract there, Burton returned to America to be brought into the Civil War as a Confederate lieutenant- colonel to superintend all their armouries. To set up a new armoury in Georgia, Burton returned to England to obtain the machinery and tools necessary from Greenwood & Batley of Leeds but, although designed and built, the equipment was not delivered. After the Confederate defeat Burton returned to Greenwood & Batley, which became a principal manufacturer of complete sets of machinery and gauges for arms production, supplying Birmingham Small Arms Company, the Austrian armoury at Steyr, the Belgian Government factory at Liège, the Imperial Russian armouries at Tula, Sestrovelsk and Izhersk, the French armouries at St Etienne, Tulle and Chatellerault, and arms factories in Sweden, Italy, Japan, Hungary and Brazil. Their basic marketing device was to advocate setting up a factory to produce a ENGINEERING AND PRODUCTION 407 minimum of 1000 rifles and bayonets per week, for which they would provide all machinery, gauges and power plant, and erect and start up the factory for about £135,000 f.o.b. in 1891. This English company learned the value of the ‘American System’, but despite its example the ideas were slow to spread to other manufacturers. In the now United States, by contrast, these production methods were adopted quickly in the making of clocks, watches, sewing machines, bicycles, typewriters and agricultural machinery. The principal reason for this difference, and for the consequent change of fortune between the American and English machine tool industries, was the shortage of skilled labour in the USA. Immigrants with skills could rapidly become masters, and for those with imagination and courage the opportunities of a good life farming in the West competed with the prospect of factory work in the East. This created the high level of wages offered and the need to build skill into the machine tools so that they could be operated by whatever unskilled labour was available. Output being so directly related to the efficiency of the operation of machinery, wages were paid under contract and direct ‘piecework’ systems, marking the beginning of ‘payment by results’ and the material success of all classes, well outstripping that in Europe. The ‘American System’, or mass production, in different industries called for many machines designed to operate at higher speeds and perform multiple operations, and for new processes to meet the needs of the product. Grinding had remained a simple process of creating an edge on a cutting tool or external finishing of cylindrical objects, using wheels of similar form to that in the oldest illustration from the Utrecht Psalter of 850 AD and work guidance by hand. New products such as the sewing machine could only be made commercially by mass production methods, and the success of these products called for greater refinement in the accuracy of their components; grinding therefore had to become a precision operation for both cylindrical and surface finishing. The first attempts to do this involved mounting a grinding wheel on the cross slide of a lathe and driving it from the same overhead shaft which powered the spindle. Several refinements in the design provided covered guideways, specially weighted carriages to avoid chatter, and a reversible, variable speed drive to the carriage. Brown & Sharpe, the great machine tool and gauge making firm of the USA produced such a grinding lathe in about 1865 for the needles, bars and spindles of the Wilcox & Gibbs sewing machine they were manufacturing. This machine required such careful control that in 1868 Joseph Brown designed his Universal Grinding Machine, the forerunner of all precision grinding machines which in turn made possible the production of accurate gauges, measuring instruments and cutting tools of all types. The success of this machine depended very largely on the use of grinding wheels which were made with emery or corundum bonded by a material to give it strength while allowing the abrasive particles to cut. In England in 1842, Henry Barclay had PART TWO: POWER AND ENGINEERING 408 experimented in producing a vitrified wheel, followed by Ransome in 1857 with a soda bond which was much more successful and Hart produced a similar wheel in the USA in 1872. Sven Pulson, also in the USA, managed to make an effective clay wheel in 1873 on the lines of Barclay’s attempt 30 years earlier. Feldspar was used in the formula when F.B.Norton patented the process in 1877, marking the beginning of progressive development of artificial grinding wheels. Small arms manufacturing also created the milling machine and, although its actual inventor is unclear, it appeared in 1818 in the arms workshop of Simeon North. According to a drawing by Edward G.Parkhurst, it consisted of a spindle carrying a cone pulley mounted between two heavy bearings with a toothed cutter on the spindle extension and a carriage, on which the work was mounted, traversed by hand underneath the cutter at 90° to its axis. Between 1819 and 1826, according to the report of an official investigating commission into the work being done by John Hall in the rifle section of Harpers Ferry Armoury, there existed plain and profile milling machines designed by Hall to cut the straight and curved surfaces of his rifle components and eliminate the handwork of filing to templates. Another machine of doubtful origin is thought to have been built c. 1827; the next, made in the Gay, Silver & Co. workshops c. 1835, incorporated an improved cutter spindle support and vertical adjustment to the headstock. Frederick Howe was trained in the Gay Silver shop and when he joined Robbins & Lawrence in 1847 he built a production milling machine based on patterns from the Springfield Armoury which resembled the basic structure of the lathe in bed, headstock and tailstock, with the cutter supported and driven between the head and tail centres. The work was traversed across the bed by hand-operated cross slide and cut applied by raising the cross slide. A development of this design with greater rigidity, made in 1852, was sold to the Enfield small arms factory in England. This design was also the one modified by Pratt & Whitney at Phoenix Iron Works into the famous Lincoln Miller supplied all over the world by 1872. The next stage in the development of the milling machine occurred in 1861, when the problem of the slow and expensive method of filing the helical grooves from rod to make twist drills was brought to the attention of Joseph R.Brown by Frederick Howe. Brown’s solution was the Universal Milling Machine which, with its knee and column construction and geared dividing head on the swivelling table, was to become the most flexible and widely used machine tool, second only to the lathe, and the basis of the Brown & Sharpe Manufacturing Company’s machine tool business (see Figure 7.9). An inclined arbor in the dividing head allowed the production of tapering spirals or straight grooves for cutting such requirements as reamer teeth and was based on Brown’s work in gear cutting. For heavier work the Brown & Sharpe Universal Milling Machine was made in 1876, with an over arm to give increased ENGINEERING AND PRODUCTION 409 support to the cutter. The pioneer milling machines of the early clockmakers used a rotary file type of cutter and, as larger gears were required, similar machines were made to match the profile of the teeth to be cut by hand chiselling and filing, following the idea of Vaucanson in 1760. These methods were inadequate for the new milling machines because the small teeth allowed only a small depth of cut and presented difficulties of sharpening. Brown solved this problem by patenting in 1864 a formed cutter which could be face ground without changing its profile. With these cutters the milling operation was fully established, other cutter development following closely: notched in 1869, inserted teeth in 1872, face milling with inserted teeth in 1884. Safety bicycles, increasingly popular in Britain and on the continent of Europe during the 1880s (see Chapter 8), were imported into the USA and were immediately recognized as candidates for mass production. Special machines were devised for hub forming, boring and threading by the Garvin Figure 7.9: Joseph R.Brown’s universal milling machine of 1861. PART TWO: POWER AND ENGINEERING 410 Machine Co. of New York. A rim drilling machine was built by Rudolph & Kremmel in 1892 which could drill 600 wheel rims in a ten-hour day. Spokes were made of wire and threaded by rolling or cutting. The cutting machine allowed a boy to thread 4000–4500 spokes a day. Thread rolling was carried out by machines made on the pattern of the Blake & Johnson, c. 1849. By 1897 bicycles were being produced at the rate of two million a year in the USA before the market collapsed when the era of the automobile arrived. The need for many small parts in these mass-produced goods encouraged the use of sub-contractors who produced specialized components on machines designed for the purpose in small workshops. Ball bearings were gradually introduced into bicycle manufacture and cycle bearing companies were formed producing balls either by rolling hot metal or turning from bar on special machines similar to the Hoffman used in England. All balls were finished by grinding, and the cups and cones were turned, casehardened and ground on a Brown & Sharpe machine or similar. The vast number of screws required for the percussion locks of 30,000 pistols had caused Stephen Fitch to design and build the first turret lathe in 1845. This had a horizontal axis and carried eight tools which could be fed into the work in turn to perform eight successive operations without stopping to change tools. This idea was so time-saving that it was rapidly taken up by other manufacturers after 1850, although the vertical axis turret became most favoured by Robbins & Lawrence, who also produced the box tool and hollow mill used in operations on the turret lathe. Automatic screwing machines followed with the invention by Christopher Miner Spencer of the brain wheel control of tool slides by adjustable cams and roller followers. His machine used the collet chuck and closing mechanism patented by Edward G.Parkhurst in 1871, which was similar to Whitworth’s collet chuck, and the production machine patented in 1873 had two ‘brain wheels’, one to control collet opening and closing, allowing the bar stock to be moved and locked into working position, and the other to control tool slides. Spencer set up the Hartford Machine Screw Company to take advantage of the great market in screws but failed to protect the ‘brain wheel’ in his patent, which allowed many copies to be made. Spencer subsequently designed a three-spindle version to make screws from wire using a radial arrangement of tools on the Fitch pattern. From this was developed a four-spindle model by Hakewessel, used initally by the National Acme Screw Co. of America to manufacture screws but from about 1906, in association with George O.Gridley, manufactured as the Acme-Gridley automatic lathe. Other automatic lathes followed; New Britain Gridley, Conematic, and Fay from different companies. Many of the mass-produced goods also required gears and, more importantly, the new manufacturing machinery also depended on the ability to transfer motion and change speeds between shafts accurately and without vibration through gears made in large quantity. The cast gears used extensively ENGINEERING AND PRODUCTION 411 in early machines and continuing in the textile industry were no longer satisfactory for high-speed accurate machining by the new machine tools. The transition between clockmaking and engineering gear production occurs in James Fox’s machine of c. 1833, which used formed tooth cutters and a screw micrometer division of the index cylinder to machine a large gear blank on a vertical spindle. John George Bodmer also patented a gear cutting machine in 1839 capable of cutting internal gears, spur and bevel in addition to external spur, worm wheels and racks, but his formed metal cutting tools were very difficult to sharpen. Whitworth’s gear cutters of 1834 were the first machines with involute cutters, geared indexing and cutters driven by a flat belt through a worm and wheel. By 1851 this type of machine was made with a self-acting in-feed and had the appearance of a heavy lathe with the headstock carrying a vertical spindle on which the involute cutter was mounted, the saddle carrying the wheel to be cut on a horizontal axis shaft with an indexing wheel. Joseph R.Brown’s precision gear cutting machine of 1855 made use of the involute form backed off gear cutter invented in 1854 and used with the Universal Milling Machine (see p. 408). A Troughton & Simms dividing engine was used to make the index plate divisions. Other large gear cutting machines were developed for engine and power transmissions such as the Gleason template system machines for cutting large spur and bevel gears. The describing generating method of producing the gear tooth profile was first applied practically by Herrman in 1877 and used a single point reciprocating tool similar to the shaper action, all the motions to generate the gear tooth being given to the blank by various attachments to make spur or bevel gears with epicycloidal or involute teeth. A similar type was produced by C.Dengg & Co. of Vienna, in a patent of 1879 for epicycloidal teeth on bevel gears. Pratt & Whitney developed an epicycloidal machine in 1880 employing a circular cutter controlled by a disc rolling on the outside of a ring representing the pitch circle of the gear. Smith & Coventry of England exhibited a describing generating machine at the Paris Exhibition of 1900, and an example of the original Robey-Smith machine designed by J.Buck in 1895, which has two cutters to work on opposite sides of the same tooth, can be seen in the Science Museum, London. The chainless bicycle stimulated the development by Hugo Bilgram of Philadelphia in 1884, of a machine to produce the bevel gears required. It used a single point cutter and obtained the rolling action by swinging the carrier of the blank around the axis in line with the apex of the pitch cone by means of two flexible steel bands passing round the control cone on the blank spindle. The gear shaper invented by E.R.Fellows in 1897 is the most significant and widely used. It employs the moulding generating principle, with a fully formed gear as the generator, hardened and with the cutting edges backed off. The machine works as a vertical slotter, with the cutting tool and gear blank rotating in mesh. The application of a worm sectioned to provide cutting edges was first used by Ramsden in 1768 for his . cutter and obtained the rolling action by swinging the carrier of the blank around the axis in line with the apex of the pitch cone by means of two flexible steel bands passing round the control. at the rate of two million a year in the USA before the market collapsed when the era of the automobile arrived. The need for many small parts in these mass-produced goods encouraged the use of. the outside of a ring representing the pitch circle of the gear. Smith & Coventry of England exhibited a describing generating machine at the Paris Exhibition of 1900, and an example of the original