When the eighteenth-century steam pioneer James Watt moved into his retirement home, he set up a garret workshop in which, among other things, he developed two sculpture-copying machines (one reducing, one same-size). The contents of the workshop, including 24 multi-part moulds for plaster of Paris copying, and over 400 medallion moulds, casts and copies were transferred to the Science Museum in the 1920s. Using this material evidence, the article investigates how this (perhaps surprising) interest in sculpture-copying may have arisen, and Watt's relations with several of the leading artists of his day - Peter Turnerelli, Francis Chantrey and others. Watt chose for his subjects both people he knew and characters from classical antiquity, using portraits, busts and even his partner Matthew Boulton's death mask. The copying machines were never finished, but working on them used many of the mechanical skills he developed in his engineering career, and gave him considerable pleasure.