Roberts built a range of machine tools, some to his own design, the first being a gear-cutting machine. For checking the dimensions of the gears he adapted the
sector, which he developed for sale to other engineers. Roberts adopted rotary cutters, which he had seen used at Maudslays. This is one of the earliest records of a
milling cutter used in engineering. In 1816 he made the first reliable
wet gas meter. In 1817 he made a lathe able to turn work . This had a back gear to give an increased range of speeds and a sliding saddle to move the tool along the work; the saddle was driven by a screw through gearing which could be disengaged when the end of the cut was reached. Also in 1817 he built a
planing machine to allow the machining of flat surfaces. Previous to this, flat surfaces were laboriously made by hand with the fitter using hammers and chisels, files and scrapers to get a true surface. File:Roberts lathe at Science Museum 01.jpg|Roberts' lathe at the Science Museum in London File:Roberts lathe at Science Museum 02.jpg File:Roberts lathe at Science Museum 03.jpg File:Roberts lathe at Science Museum 04.jpg Following the success of
his power loom, in 1825 he invented a slotting machine to cut keyways in gears and pulleys to fasten them to their shafts. Previously this was done by hand chipping and filing. The tool was reciprocated vertically, and by adopting Maudslay's slide rest principle, he made the work table with a universal movement, both straight line and rotary so that the sides of complex pieces could be machined. Later, he developed the shaping machine, where the cutting tool was reciprocated horizontally over the work, which could be moved in all directions by means of screw-driven slides. Examples of his machine tools, including the oldest existing
metal planer, are in the collections of the
National Museum of Science and Industry, London. Roberts also manufactured and sold sets of stocks and dies to his range of pitches, so other engineers could cut threads on nuts and bolts and other machine parts. Roberts' inventions had a seminal influence on other machine-tool engineers, including
Joseph Whitworth when he came to Manchester a decade later. ==Textile machines==