of unprecedented precision and accuracy. The next year he added his self-adjusting centre chuck to the lathe, for which the Society of Arts awarded him their silver medal. The same year (1828), Clement began making fluted screw-cutting tap and dies and urged the adoption of a standard system of screw threads where every machine screw of a particular diameter should have a set number of threads of a predetermined pitch and determined the number of threads for each diameter of bolt. Joseph Whitworth, at that time one of Clement's journeymen afterwards played a major role in such standardisation, the Whitworth thread becoming a standard for machine screws. Regarding Clement's building of planers, Roe (1916) says, Clement made his first planer in 1820 […]. Some years later he built his "great planer," a remarkable machine from both a mechanical and a financial standpoint. A very full description of it was given by Mr. Varley in the "Transactions of the Society of Arts" in London in 1832, illustrated by a set of copper plates made from Clement's own drawings. Clement's reputation of being the most expert draftsman of his day is well borne out by these drawings. […] It was fitted with centers and was used for planing circular, spiral and conical work as well as flat work. It took in work 6 feet square and was hand-driven. […] For more than ten years it was the only one of its size and it ran for many years night and day on jobbing work, its earnings forming Clement's principal income. Involvement with Charles Babbage The recognised excellence of Clement's machine tools and his skill in precision engineering led to him being employed by Charles Babbage in 1823 to work on his project to design and build his mechanical calculating device, the difference engine. The high prices of his large precision tools led to a falling out with Babbage (at the time workmen were allowed to keep any tools made by them in the course of their work), but his skill and the quality of his products kept him in employment for many years. Later years In later years, Clement returned to music and constructed an organ. He died on 28 February 1844 at 31 St George's Road, Southwark. Although he had never married, he had a daughter, Sarah Clement, by one Agnes Esson from County Durham. References Bibliography Oxford Dictionary of National