Early "top-oiler" headstock picture cut away (with the backgear guards removed) to show the ball thrust bearing inboard of the left-hand headstock bearing. A fibre washer was placed between the adjustment "screw-ring" on the outside of the bearing and the headstock casting; this can, with advantage, be replaced by a standard radial needle-roller bearing thrust bearing that comes complete with hardened washers to mount each side. The use of this type of bearing allows the spindle end float to be reduced from 0.001" to almost zero--however, because these very thin needle-roller races have to use parallel rollers (instead of the usual tapered type) the outside of each roller is moving faster than the inside and some compensatory skidding has to take place. It is thus vital to leave a few "tenths of a thou" clearance to allow for heat expansion and give the rollers chance to "find their place".

Ball thrust bearing inboard of the left-hand headstock bearing.

The various and changing specification of headstock spindles and bearings on the 9-inch lathe are a little difficult to untangle. In early catalogs, rather than own up to the fact that the spindle was running directly in the cast iron of the headstock, South Bend either admitted it by omission - or referred to the subject only obliquely (they must have imported a political-speech writer, for they did this very successfully) - however, they need not have been so shy, the method, widely employed on other makes of lathe and machine tool had already been proved a success. What South Bend did was match the specification of the spindle to the type of use it was likely to encounter: thus, on its introduction in 1934 the 9-inch "Workshop" lathe was fitted with a ground steel spindle that could be ordered hardened for an extra $10, a charge later reduced to $6. By 1940 all the 9-inch lathes were fitted with an "alloy steel" spindle with its bearing surfaces carburized, hardened and ground - but with the 12-speed and "Toolroom" models being "Superfinished" to a smoothness of 5 micro-inches ( .000005" ). The spindle ran directly in cast iron of the headstock and, if provided with clean oil (Mobil Velocite 10 is recommended), and not run beyond its deign limits, proved capable of lasting a very long time indeed. As a matter of interest, though never mentioned in any contemporary catalog, some 9-inch lathes left the factory with thin-walled bronze bearings - which have only been discovered on stripping machines down.

The standard spindle for the 9-inch Workshop lathe was bored through 0.75". The front bearing was 113/16" in diameter and 21/4" long - and the rear 13/8" in both diameter and length. However, on its introduction the spindle nose was 13/8" in diameter with a 10 t.p.i thread but this was quickly changed to the familiar 11/2" diameter 8 t.p.i U.S.F thread. The Taper in the spindle of the original machine appeared to be a No. 3 Morse and was supplied with a sleeve to bring it down to a No. 2. The advent of the larger spindle allowed the fitting of what seemed to be, at first sight, a No. 5 Morse taper, again with a reduction sleeve. However, South Bend's specification for this part differs from the "standard" Morse of  0.6315" per foot and used instead 0.602" per foot. Hence, if the sleeve adaptor is missing the right one will have to be acquired (try Scott Logan at www.lathe.com). The same taper was also used on the Light 10, (Heavy 10, 13-inch, 14-1/2-inch and 16-inch lathes.
Owners also report examples of lathes with (8 t.p.i) spindle-thread diameters of 11/4", though this figure has yet to be found in a catalog specification.
The relatively large spindle bore meant that a collet adaptor could be fitted inside the spindle, and draw-in collets used with either a screw or lever-action closer.

Section through the V-belt drive headstock showing the handwheel collet assembly. This is an earlier model with top-mounted oilers