Based for many years in Geneva, Switzerland, and working from their Plainpalais and Châtelaine factories, SIP - Société Genevoise d'Instruments de Physique - was established in 1862 to produce scientific apparatus and precision measuring instruments. After some confusion from the French-based International Bureau of Weights and Measures - who kept the "master metre" bar and two witness bars in their vaults but seemed unable to provided subdivided replicas to National Governments - SIP was called upon to produce working standards for the International Bureau, the Bureau of Standards in Washington and the National Physical Laboratory  in Teddington, England (and other important metrological institutions).  The result was a very high precision steel ruler -  a standard scale - by which other length-measuring instruments could be calibrated and these were sold in considerable quantities to Government, engineering, scientific, and metrological institutes worldwide. With this background SIP eventually moved into machine-tool production, their first effort being a watchmakers' "Pointing Machine" developed between 1910 and 1919 -  a device that proved to be the immediate forerunner of the now ubiquitous jig borer. The exact date of the first true jig-borer's manufacture appears uncertain, but was not before 1919 and possibly as late as 1921 - an MP-5 (Serial Number 2) being delivered to the Royal Small Arms factory at Enfield, in north-east London in 1922. From this point the range was developed to include a number of sizes and types, the most common pre-WW2 models being the No. 3, MP-4B, MP-5B, MP-6, MP-6B (vertical and horizontal heads) and Hydroptic. Other products included standard-type and one-off optical measuring machines, some for length, others with three-axis (three co-ordinate) capability and varying in size from bench-top models to large floor-standing machines with tables up to 61.75" x 40.5". Circular and linear dividing machines were also listed (and often built to special order for use by Government agencies); rigid-frame and bench micrometers, shop gauge measuring machines (for checking the accuracy of slip, screw, and snap gauges, micrometers, plain and limit plugs) micro-indicators, high-precision micro indicators for tiny parts, gear-testing machines, micrometer microscopes, spectrometers, X-ray spectrometers, electro-magnets, printing and recording chronographs (time-based recording) precision scales (often built to order) and cathetometers. A small range of special lathes was also made, but not for use as production machines, these were intended only for the correction and testing of very accuracy screws, thread gauges and taps, etc. With such a diverse range of practical and scientific skills and experience to call upon - they even made their own roller spindle bearings - no wonder that SIP were able to design, manufacture and market, in considerable volume, some of the world's most accurate machine tools.
From its earliest days, when it was a corollary to the Swiss watch and clock industry, SIP quickly established a reputation for work of the highest order and, by 1959, in a never-ending search for improved accuracy, had developed a photoelectric Comparator (dividing machine) upon which many countries chose to have their "Weights and Measures" length standards calibrated. The same SIP device was also chosen for the "International Bureau" and allowed measurements down to an accuracy of better than half a millionth of a metre. Today, although mechanical measures are in theory obsolete - the first move away from this being to base length measures on the wavelength of krypton - they still provide much of the practical hands-on basis for general industrial use on the shop floor. Metrology - the technology of measurement - is wide and complex subject and rewards extra study.
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As the reason for a jig borer's existence is its the ability to position a workpiece with great precision, makers invested many years' work into producing high-quality, ultra-precise mechanical and mechanical-optical measuring systems. Prior to the 1920s (and as used in earlier locating machines developed in Switzerland around 1910) very accurate leadscrews were employed that had scales calibrated down to 0.0002" (0.005 mm) on the smallest models and 0.0005" (0.015 m) on the largest.  However, only the Moore Jig Borer Company in the USA could produce, on a commercial basis, screws that were pitch perfect over the whole of their (maximum 20-inch) length and required no compensating correction mechanism. Hence, though of a very high standard, even SIP required some method of automatically modifying their micrometer dial readings. The solution was to check, with great precision, how far turning the screw actually moved the table - and to do this it was necessary to measure the travel very accurately, in small increments. The obvious candidate for a reference was, naturally enough, one of SIP's own standard scales and, with a microscope attached to the vertical spindle, the graduations were read through it as the feed-screw was turned. The tester recorded the simultaneous readings from micrometer dial and standard scale and prepared a "curve of errors" that was reproduced, in an enlarged form, on a strip of hardened steel permanently fixed alongside the table (and other moving elements). As a slide moved, a small lever followed the strip's profile and transferred its (tiny) movements, via a rod held in brackets, to another lever at the other end. Connected to the last lever was the vernier scale, positioned next to the rim of the feed-screw micrometer dial and free to move relative to it. Thus, for any position a corrected setting was automatically obtained - though great care in taking the vernier reading was, of course, essential. This ingenious (but simply engineered) system is believed to have been first employed by SIP in their jig borers during the 1920s - and ensured that the positional accuracy of a complete machine was greater than that of its precision feed-screws.
Following the introduction of the first SIP full-size jig borer in 1919 (and their steady development during the 1920s) the Company decided that a standard scale should be built into the body of the machine and its graduations read directly through an optical system with the results displayed on an illuminated screen. The first such model, the Hydroptic, was announced during 1934 and (because feed screws were no longer needed) incorporated a further refinement, the table was moved hydraulically to give a particularly smooth and powerful drive. This model proved an enormous success and the standard scale method, combined with external rulers, micrometer drums and vernier scales, was to provided toolrooms with the most accurate way of determining a position until the introduction of the Coordinate Measuring Machines (CMM) and Digital Read-Out (DROs) systems.
An important point about accuracy is that SIP's measurement of a jig-borer's precision was its "accuracy of displacement": this expression referring to the difference between the maximum positive error (+) and maximum negative error (-) of any two coordinate positions with the working range of the machine. It did not concern repeating accuracy, or the precision of the dial readings.
Most larger jig borers, of every make, were designed along lines similar to those of the well-established planing machine - a fact alluded to in some SIP advertising literature - where a large sliding T-slotted table was arranged to pass between two upright castings joined by an elevating bridge that carried a single or several toolholders. This arrangement proved immensely successful for, not only could large jobs be accommodated, but also ganged-up set of smaller ones - for example lathe beds - all machined by multiple tools (sometimes fastened to the uprights as well) in an astonishingly short time. The design was soon adapted so that powered  heads replaced the simple fixed cutters - in which form it was generally known as a plano-miller. Other versions included massive open-sided models for accommodating huge jobs that overhung one edge - and even tiny table-top models for use by amateur engineers. However, what exactly is a jig borer? As may be deduced from the previous paragraphs, it is really a combination of a measuring machine and machine tool - both of extremely high precision. Naturally, the required accuracy of any machine tool needs to exceed that of the job it produces and, if that task is the precision drilling of holes in exact relative alignment, as found in jigs and fixtures used in mass-production processes, the machine must be designed and built to the highest possible standards. Therefore, as its name suggests, the jig borer was originally intended for just that one onerous task - machining multiple holes in exact alignment in order to make jigs. However, it was quickly discovered that the design was far more versatile than originally conceived and could be used, like a miller, to machine components directly - to an astonishing degree of accuracy - and even be employed as a precision measuring instrument to check jobs done on other machine tools or by hand.
One important advantage of the jig borer was its speed of setting compared with the traditional "button-method" of hole location. In the 1930s, having established a range of three machines, the Types MP-4B, MP-5B and MP-6, SIP published an interesting comparison of the time needed to mark out four holes of 20 mm in diameter and spaced at distances of 100 to 150 mm. SIP reckoned around six hours for a highly skilled toolmaker using "buttons" - but only 29 minutes employing what was described as a mechanic of medium skill when using a jig borer. Even if the toolmaker could have worked twice as fast as SIP claimed, and the jig-borer operator taken twice as long, this would still have made the latter process three times quicker (a figure actually quoted in a letter to SIP from a Birmingham engineering company). More telling still was the accuracy claimed: to within 0.02 to 0.04 mm (0.0009" to 0.0016") for buttons and to within 0.005 mm (0.0002") for the jig borer. So accurate is the jig borer that, to function correctly and within the maker's limits, it required a specially constructed foundation inside a temperature-controlled room and positioned so that the thermal properties of its surroundings are consistent. Sunlight should not be allowed to fall on it, nor should other machines, radiating heat or vibration, be positioned nearby.  Naturally, some jig borer operators are better than others and a man with considerable experience together with a highly-developed feel, can coax even better results from a machine, the estimation of a reading around the 0.0001" mark and the actual dimension at the end of the cut being of critical importance.
From the early 1930s, SIP supplied machines in metric measures calibrated to be accurate at 20°C and for "inch" countries at 62°F for the United Kingdom and 68°C for the U.S.A.
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By the 1930s the Swiss had become the leading European exponents of jig-borer technology and, indeed, so important was their contribution to British Industry that, during the final years of the run up to WW2 (1939-1945) the British government forged very close ties with SIP as they struggled to build "shadow" factories for war production away from established industrial areas. The result was the opening in 1940 of a "factory-supported" rebuild facility at Wooburn Green, near High Wycombe and then, in 1945, of a factory in Newport Pagnall where numbers of the little but so useful MP-3K were manufactured, the main frames being imported from Switzerland. This was the first factory outside Switzerland to make SIP machine tools and showed the high regard with which the English organisation were held by the parent company. Machining of the major parts was undertaken by Markyate Engineering (based in Markyate, just south of  Luton and Dunstable) a well-known precision engineering company who had a number of very large SIP jig borers in their works.
By the early 1950s - and under competitive pressure from Ferranti with their ingenious and revolutionary Coordinate Measuring Machine (CMM) designed by  Harry Ogden and David Williamson - SIP developed a positioning system by which means an automatic and completely accurate setting of the table and spindle-head saddle could be achieved using photo-electric microscopes that read the standard scales directly. Alongside their involvement in machine-tool applications, SIP were also introduced, via the English branch, to a linear displacement electronic transducer system made by Reilly Engineering of Guildford, Surry.  So impressive was the system, and with such enormous potential, that in order to obtain the patents and know-how, SIP bought Reilly and changed it name to Servomatic Hydraulics (Guildford) Ltd. Eventually, in 1961, SIP began manufacture of their own CMM, the SIP 560M. The company were also early to incorporate digital read-outs and NC (numerical control) and other electronically-assisted systems. One of the first in the field were Sperry, whose NC punched tape-controlled computer (Type CN-4) was used by SIP to provide automatic positioning of the table and spindle-saddle and spindle cycle control. A separate system labelled DIR (not able to be used in combination with the Sperry) could memorise, on a magnetic medium, an operator's initial control movements for subsequent reuse when the job was repeated. Since those early developments, computers and digital read-outs have, of course, been used extensively to improve every aspect of machine-tool operation to the extent that the stand-alone jig borer is, in effect, obsolete. An example would be the floor-to-floor time to machine the crankcase of a V-twin motorcycle engine: conventional, hand-operated vertical milling machine (with tea breaks): 5 hours; multi-spindle auto (part-finished job) 1 hour: tape-controlled jig borer: 30 minutes; early CNC machining centre: 12 minutes; the latest multi-head, multi-tool machining centre with robot loading and unloading: 50 seconds - and improving. However, many older jig borers have been successfully retrofitted with Fanuc, Heidenhain and other CNC controls and their productive life greatly extended.
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The SIP optical system differed over the years, this "all-line" type avoiding the use of micrometer-mounted vernier scales. The reading, easily worked out,  is 7.43145", that is, accurate to five one-hundred thousandths of an inch. With some experience, operators could routinely work down to within  0.00001"

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By the late 1950s OUTPUT of SIP machines was beginning to reach its zenith, with eight different models in production, all based upon a clear lineage, though of continuously improved design. The range could be divided into three groups: very high-precision, smaller single-column machines; general-purpose, heavier twin-column models and massive "Hydroptic" versions with hydraulic drive.
Smallest was a pair of single-column models, the No. 1H and No. 2P  - the former with a 16" x 10" (400 x 250 mm) table and the latter 27.5" x 12.5" (700 x 317 mm) - each presumably developed to compete with similar machines from Hauser, whose range encompassed only less-massive machines. First of the conventional twin-column models was the No. 3K, with a 20.5" x 15" (520 x 380 mm) table, a model also available as the 3K-CN with the (previously-mentioned) Sperry and other types of electronic positioning control. The No. 4G was substantially larger, with a table 27.5" x 23.625" (700 x 600 mm) while the No. 5E (described by the makers as a medium-size machine) had a 35.5" x 30.25" (900 x 770 mm) table and was designed to provide a typical iobbing engineering company with a borer capable of tackling the most common jobs. Another version of the 5E, introduced with the advent of Digital Readouts (DROs) was the 5EA. Identical in all mechanical; respects to the standard model, it featured a read-out panel mounted on a separate stand that could be moved to any convenient position.
Larger still, and incorporating some advanced features, were the popular Hydroptic-6 and 7 and the improved 6A and Hydroptic-7A types with tables 43.25" x 33" (1100 x 842 mm) and 61.75" x 40.5" (1570 x 1024 mm) respectively. These heavy, rugged and long-lasting models were most likely to be found working in larger firms engaged in the production of critical components for aircraft, missiles, ships' engines, fighting vehicles and such like - where the facility to manufacture big jigs, or machine awkward components directly on the borer, would have been required. Initially, two forms of computer control were available, the models so equipped being the 6A-CN and 7A-CN when fitted with Sperry automatic table and spindle-saddle positioning and 6A-DIR and 7A-DIR with memory and playback of the operator's control movements.
Two unusual versions of the 6A-DIR and 7A-DIR were also produced (though it is reported that only ten of each were made) built to the specification of a three-coordinate measuring machine. Sold as the Superoptic-6AM and Superoptic-7AM they had electronics built in to automatically put the measuring line in the middle of the "pickle fork" -  to within the astounding accuracy of  0.000005".
Largest in the SIP range of the 1950s and 1960s was the Hydroptic-8P, a version intended for production work and fitted with both vertical and horizontal spindles to make the best use of its considerable capacity. With a 61.75" x 40.5" table, this too was available with an automatic coordinate repeater thought not, it is thought, a contemporary NC control system.
Although as late as the 1970s the older types of machine still continued in production - the MP-3K, MP-5E, 6R, 7R and Hydroptic-6A and 7A - by then these had been joined by two CNC machining centres, the 8000 and 400. In early 1973, with increasing competition in the market, SIP joined forces with their long-established Swiss rivals Hauser - and DEA, makers of inspection centres with read-outs and computer controls. By the mid-1980s the original SIP designs had ceased production, to be replaced by the dual manual/computer control SIP-640 and SIP-740 and a range of Hauser-based models the MP42DR, MP52DR, MP44 and MP54 and two jig grinding machines, the S40 and S50..