J. Hubert Davies, son of John Hunter Davies and his wife Emily, showed an aptitude for invention from an early age. He worked in a merchant's office for ten years and received a sound commercial training. During the latter part of this period he studied mechanics, physics and chemistry in his spare time. In 1882 he set up a small workshop and laboratory for electrical and chemical research, but lack of funds led him to an appointment in a drawing office in 1883. In 1887 he resigned to develop certain inventions, which he patented. He returned to the same drawing office a year later as chief draughtsman and electrician.
Davies came to Johannesburg in 1889 to supervise the erection of electric light plants for three gold mines and was retained as consulting electrical engineer to messrs Howard, Farrar and Co. He established the mechanical and electrical engineering firm of Hubert Davies & Company, which was probably the first electrical firm to be established in southern Africa. In the latter half of 1891 he erected one of the first electric light plants on the mines, at Brakpan Colliery. Nearly a year later the Johannesburg Lighting Company got its first electrical machinery working, with Davies as the company's consulting engineer. From that time he was associated with most of the pioneer electric lighting and power plants on the Witwatersrand, either in a consulting capacity or as contractor. About 1895 or 1896 he took Mr William Spain into partnership and the firm became Hubert Davies & Spain until the partnership was dissolved in 1907. They opened a branch in Durban in 1900, another for some years in Pretoria, and established a buying office with engineering staff in London. After 1907 Davies also opened branches in Cape Town and Salisbury (now Harare, Zimbabwe), making the firm probably the largest of its kind on the sub-continent.
Davies was a member of the (British) Institution of Electrical Engineers and of the Institution of Mechanical Engineers, and an associate member of the Institution of Civil Engineers and of the American Institute of Electrical Engineers. In Johannesburg he became a foundation member of the South African Association of Engineers and Architects and a member of its first council for 1892/3. He remained a member of council for two more years and served as the association's president in 1896/7. On 27 July 1892 he read the very first technical paper before the association, on "Electrical transmission of power" (Proceedings, 1892-1894, Vol. 1, pp. 5-13). In this paper he pointed out the advantages of generating electricity at a central generating plant on a mining property, and transmitting it to where it was to be used, compared to generating power wherever it was needed or transmitting it by mechanical means. The paper was followed by a demonstration of the application of electricity to which all local mine managers and engineers were invited. The demonstration plant consisted of a tractor engine driving a 20 kW bi-polar generator, which supplied power to various electric motors driving lathes, pumps, and a model 5-stamp battery. Later that year, on 30 August, he read a second paper, on "Blasting with electricity" (Proceedings, 1892-1894, Vol. 1, pp. 52-54). At subsequent meetings of the association he took members to visit the works of the Johannesburg Lighting Company (27 September 1893), and the electrical plant at the Crown Reef Gold Mining Company (7 April 1894). During 1895-1896 he built and equipped an electric surface haulage at the New Modderfontein Gold Mine, including an electric locomotive driven by two bi-polar motors.
Davies was an early member of the South African Association for the Advancement of Science and served on the committee for Section C (including engineering) at the association's annual meeting in Johannesburg in 1904. He remained a member to his death. He was married to Christina M.L. Davies, born Jaski-Carst, with whom he had two surviving children.