John Stark Senior:Originator and Pioneer manufacturer of the "Spring Chuck" Lathe.

The Early Stark headstock - like that of all early Precision Bench Lathes - used a developed version of the design originally standardised for watch lathes where a hardened, ground and lapped spindle ran in glass-hard steel bearings - the very best combination of materials and manufacturing techniques available in the late 1800s and originally advertised by Stark as being manufactured from English steel.
The version of the Stark headstock illustrated above took the design one stage further with the inclusion of a ball-bearing race to absorb spindle end thrust; in order to set the bearing - and so relieve the front bearing B of  excess longitudinal loads - the normal adjustment of the spindle bearings by a screwed ring at R was first carried out. The bearing cap C was then rotated until it brought the outer race of the bearing E into contact with the headstock casting at D; the milled-edge locking screw H - which passed through the assembly to press against the adjusting thread - could then be tightened to hold the setting. The result was that end loadings were taken on the plate E, which remained stationary, whilst the inner race F rotated with the spindle.
A patented arrangement of a ball race to take the end thrust on the collet draw tube (I)  was also used on this headstock.