All Logan lathes had spindles supported on grease-packed ball-races , with the preload set by the bearing manufacturers. Although the headstocks of the 9", 10" and 11" machines were of very similar appearance and design, the 11" model appears to have been fitted with the heavier, larger-bore spindle from its bigger brothers but with a single-row bearing at both front and rear.  The 12" and 14" lathes both had more massive headstocks in line with their much heavier-duty capacity. The precision bearings were manufactured by "New Departure" and allowed Logan to claim, for these models, a total run-out of within 0.0005" twelve inches from the front bearing.
On early 10-inch lathes there is a flat "spring-ring", grooved into the outside of the outer race, that bears on the headstock casting for thrust; a 3-bolt cover fits behind the swarf deflector on the spindle and clamps the ring to the headstock. Swarf deflectors are now unavailable for either bearing, so it is best not to remove them - even if this seems necessary.
A tight sliding fit in the headstock the front bearing is held to the spindle by a threaded ring with (as it is built in) no externally-applied preload necessary. The rear bearing, which simply presses into the rear carrier on the headstock, is located by spacers and a nut on the spindle end..