Mr. R.H.St John had two watch lathe patents to his name, No. 18,213 granted on September 15th. 1857 and No. 23,406 granted on March 29th, 1859.
Using a pair of traditional watchmekers' 'turns' as the basis for his invention, St.John proposal was for a method of centering work. Like those proposed by other inventers in the 1800s, including Jackson, Shaller, Hopkins and Kesselmeir, it was not an automatic system and required the operator to manipulate the assembly in order to achieve the desired  alignment. In the case of St. John's patent this included: "...by taking in hand a suitable, small piece of wood it is applied against the side of the centre point, and as the chuck is made to revolve, by regulating the pressure of the piece of wood the article in the lathe may be readily brought to a true horizontal position, at which point, the screw jam disk is tightened, which tightening, effectually draws up the disk f, f, and brings the centering plate I, flush up against the shank or key part of the mandrel, C, which holds the plate I.I. And prevents its slipping out of true…"
At least one lathe by St John survives - though sadly without his patented chuck attached - and is shown towards the bottom of the page together with its patent papers..