Maker's Logo pre-1929                        Maker's logo post 1929

Described by its makers as the Utility School, Garage and Repair-shop Lathe, the machine immediately below, a Sebastian 15" (circa 1910 - 1926) was the Company's cheapest offering and, in its basic form, lacked a compound slide rest, the tailstock did not set over for taper turning and the bed lacked a gap. However, a friction-type countershaft unit was included in the price as well as a tool post,  faceplate, drive plate, changewheels for screwcutting and a small tool kit. As with modern cars (especially BMW) everything worthwhile was on the options' list and by spending more it was possible to specify all those small but important extras.
Although in its lowest-cost form this model was reduced to the fundamentals required for a useable, screwcutting centre (engine) lathe it was still reasonably specified and would certainly have fulfilled many requirements when installed in a school or training workshop. The true swing was 15.25", it was properly backgeared and screwcutting was through a conventional tumble-reverse mechanism that allowed both left and right-hand powered movement to the carriage by altering the position of just one lever. As standard it accepted 40" between centres, but any capacity could be ordered, in foot intervals, up to a maximum of 88" - when it is hoped that a central bed support might have been included ……
The spindle, which ran in white-metal bearings, had a useful 15/8" hole and a No. 3 Morse taper centre.
Some models appear to have had the leadscrew clasp-nut lever on the right-hand side of the apron, while on others it was positioned to the left..

Sebastian 15" Utility  with Detachable Gap Bed
Removing the 8.5" long gap section increased the centre height by 3.5" and meant that work swung on the faceplate could be up to 22" in diameter.

Sebastian Utility lathe with optional self-contained countershaft unit and drum-type electrical reversing switch. Unusually, the spindle is fitted with a T-slotted faceplate - something not often found on cheaper lathes.

Sebastian 13" Gold Seal Geared-head, Quick-change lathe of the late 1920s
A screwcutting gearbox, power sliding and surfacing, fully enclosed and clutched drive unit, quickly removable chip tray, drum-type reversing switch all add up to a machine which was well specified for its year of manufacture.
Although pictures above and the two belowe show essentially the same lathe (and all were listed in the same catalogue), the one at the top, built in the late 1920s, represents some twenty five years of development over its older brother at the bottom.
While the bed, tailstock, the entire carriage assembly and screwcutting gearbox were identical the stand and geared headstock of the newer machine were entirely different. The motor-drive unit was contained within the headstock-end cabinet leg and perfectly reflected the contemporary move towards self-contained lathes - which could be installed free from the need to assemble and install a separate countershaft unit, or hook them up to an overhead line shaft. A clutch was built into the end of the headstock input shaft, and was conveniently controlled by a levers at both the headstock end of the lathe and from the right-hand side of the apron. Time-and-motion studies had long shown that, whilst taking one step to alter a control might, typically,  waste only four seconds of time, if the poor operator had to do it two-hundred times a day, and there were three-hundred turners in the factory, you were looking not at minutes of lost production in an eight hour shift but sixty-six hours - or another eight workers
Much better able to handle heavier cuts at higher speeds than the flat belt drive, the geared headstockmodel would certainly have quickly paid back the greater expense when used for production. The only weakness in such a strongly-built machine as this might have been the tumble reverse system, which, by its very nature, meant the use of gears on shafts with support on one side only.

Sebastian 13" Gold Seal Belt-drive, Quick-change lathe of the late 1920s. This lathe is fitted with what the makers described as their "Bracketed Cone Head Motor Drive" - or, in plain English, a built on countershaft unit fitted, in this example, with a clutch built into the hub of the large pulley on the end of the countershaft. The handwheel on the front of the headstock cabinet leg was used to adjust the tension of the primary drive belt.

Early Sebastian 13-inch lathe
  Typical of the Centre or "Engine" lathe made by many manufacturers from the late 1800s until the late 1930s, the basic flat-belt drive Sebastian, with separate countershaft, was eventually relegated to the economy end of the Company's range by the introduction of  geared headstocks and self-contained motor-drive systems.

Sebastian 12-inch short-bed lathe with a geared headstock holding Timken taper roller bearings
Sebastian made a range of geared-headstock lathes of unusually short bed length. Several models were available, all fitted, as standard, with a screwcutting gearboxes, dial thread indicator, power sliding and surfacing and a built-on countershaft unit with a clutch. The toolroom model was provided with taper turning and a full draw-in collet set.
A version for bench mounting was also produced, which stood on two stubby feet.
On such a short bed the saddle became disproportionately long, and must have evened out bed wear to a most satisfactory degree …..

A less expensive Sebastian 12-inch geared headstock with plain bearings as sold for use in schools and training establishments