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.