In engineering, quantity production is possible only with fine, repeatable measurements. Starting from a problem in aerospace, David McMurtry, who has died aged 84, did much to advance the scientific study of measurement – metrology – and so facilitated hi-tech mass production in many fields.
While working for Rolls-Royce in 1972 at its Filton factory, near Bristol, on the Olympus engines used in the Concorde supersonic airliner, McMurtry became frustrated with the foibles of the existing coordinate measuring machines (CMMs). One morning he arrived at work with a home-modified measuring probe that could cope with the complex task of properly measuring the twisting aerofoils of the Olympus fan blades – data needed to ensure that engine reached the required performance.
To make these measurements was tiresome. The probe needed to successively touch the object being measured at many different points in order to map its form. Often the probe would bend or break, or the object being measured would move, and days’ worth of measurements would be lost.
McMurtry’s invention was to create a more sensitive spring-loaded probe that worked by breaking an electrical contact. This electrical connection could then be used to control the CMM and capture the data point, considerably simplifying and speeding up the whole process. Prior to this, CMMs were expensive, and mainly used by standards laboratories like the National Physical Laboratory (NPL), or hi-tech companies like Rolls-Royce who could afford the high overheads inherent in such systems. His idea changed CMMs from instruments of last resort to ones widely used globally in manufacturing workshops.
This key invention, the trigger probe, led to a revolution in the measurement of complex three-dimensional objects like turbine blades, enabling the accurate measurement of machined components and finished assemblies. The resulting advance in manufacturing technology provided a secure funding stream for a host of allied technologies that underscore the role of precise measurement in our increasingly technological world.
It was only when outside interest prompted McMurtry, with colleague and future business partner, John Deer, to consider directly supplying their probes that they stumbled on their true monetary value. The device proved so profitable that it funded the establishment of a world-leading supplier of metrology equipment, Renishaw plc, which turned over £691m last year and employs more than 5,000 people worldwide.
The company went on innovate with additive manufacturing, or metal 3D printing. One of its applications lies in maxillofacial reconstruction where part of an injured person’s facial bones have been lost. A computerised tomography (CT) scan is used to create a titanium replacement with a foam-like inner structure to mimic actual bone so the implant will integrate into the facial tissues more effectively.
The medical products division has developed a machine that can accurately position sensors deep within the brain to both monitor and stimulate areas associated with seizures. This offers the prospect of minimally invasive treatment for epilepsy.
Renishaw’s measuring tools are used in the manufacture of the latest cutting-edge products – semiconductors, display screens, solar cells, aircraft and aero-engines among others – anywhere where the most precise components are required. For instance, in a mobile phone, McMurtry should be thanked for the case, the screen and even the packaging of the electronics that hide behind it.
This is a logical progression for a country which was one of the first to industrialise but no longer has the low-cost labour base to compete in high-volume industrial production. Metrology was pioneered in Britain: from 1800 the great engineer Henry Maudslay developed ultra-precise measurement, and the Science Museum in London displays today a version of his bench micrometre that he nicknamed “the lord chancellor” – the ultimate court of appeal for measurement in his works.
Renishaw exports more than 95% of its production and manufactures primarily in the UK, mainly centred around South Gloucestershire and Cardiff with additional capabilities in Dublin, Stuttgart and Pune. The company has never outsourced manufacture, preferring to perfect processes at its New Mills HQ campus at Wotton-under-Edge, Gloucestershire.
Born in Dublin, David was the son of Margaret (nee Plowman) and Frederick McMurtry. After leaving Mountjoy school in 1958 he moved to Britain, and embarked on an apprenticeship with Bristol Aero Engines, later Bristol-Siddeley Engines, which in 1966 was purchased by Rolls-Royce.
Once he and Deer had started Renishaw, he served as chief executive until 2018, and executive chairman until 2024. He was knighted in 2001.
That was also the year that he got planning permission for Swinhay House, near Wotton-under-Edge, a £30m futuristic home with a dancefloor that can change into a swimming pool, a winter garden and a viewing tower. As a side interest, he founded McMurtry Automotive, and the McMurtry Spéirling electric single-seater car holds the current Goodwood festival of speed hill-climb record.
A quiet, modest and polite man, McMurtry saw his wealth as a means for pushing the boundaries of engineering. At lunchtime he could be found queueing with the rest of the employees in the canteen, paying like everyone else and sitting chatting to fellow engineers.
In 1966 he married Terry (Teresa) Adams. She survives him, along with their children, Richard, Ben and Yvette.
• David Roberts McMurtry, mechanical engineer and businessman, born 5 March 1940; died 9 December 2024
