Samuel Varley of Clerkenwell was a watchmaker, instrument maker, and scientist.
Born 24 Oct 1744.
Died 18 April 1822.
1825 Samuel Varley's method of cutting screws in the lathe was described by his nephew Cornelius Varley [1]. The lathe spindle was provided with several short threaded portions which provided a range of thread pitches (four are shown in the illustration). The lathe was equipped with a sliding flat bar alongside the headstock, guided to move parallel to the lathe axis. Fitted to the left hand end of the bar was a guide pin, which could be pushed into contact with the selected threaded portion. The right hand end of the sliding flat bar carried a tool holder. This held a form tool (a chasing tool) which was manually pushed against the workpiece to cut the thread. The guide pin and the toolholder were supported on the underside. Varley probably developed the method before 1800.