Little is known of the early life of Lewis Thomas (c.1759-1833), but by 1788 he had joined William Harwood in an ironmongery business (Harwood & Thomas) at Market Place.  They sold an assortment of locks, hinges, brass work, and other hardware (Sheffield Register, 10 May 1788).   In 1801, William Harwood, George Johnson, and Lewis Thomas registered a silver mark at 12 Howard Street.   The London Gazette shows that Harwood and Thomas continued to work together in several partnerships, which included Samuel Bennett (dissolved 1813), George Johnson (diss. 1815), and Charles Heaton (diss. 1818), John Watson, Pass & Co (diss. 1822).  These firms sold pen and pocket knives, table knives, and silver plated goods.  Lewis Thomas (like Harwood) styled himself as a merchant and was probably never a working cutler.  He lived at George Street, but by the 1820s resided at Fieldhead, Heeley Road.  

The partnership of Lewis Thomas and William Harwood ended with the latter’s death in 1823.  By 1828, Lewis Thomas & Son was listed as a merchant and manufacturer at George Street.  Lewis’s son (by his wife, Jane) was John Tarrand Thomas (1799-1880), who had been baptised at Queen Street Independent Chapel.  Father and son ended their partnership in 1830.  Presumably, Lewis Thomas had retired.  He died on 3 February 1833, aged 75, and was buried at Ecclesall.  His widow, Jane, died on 1848, aged 78, and was buried in the same cemetery.  John Tarrand Thomas (see Broomhead & Thomas) prospered as a Brazilian merchant.