The spindle

The B2 spindle with it's adjustable bearing and 8mm collet insert. The thread of the mandrel is 16G which is 20mm - 16G,  so the aperture for threaded items is metric, Pittler was apparently requested by the UK to provide Whitworth threads for the imported lathes which Pittler provided, however apertures for faceplates chucks etc could not be altered so they remain in  metric. Oddly enough I recently obtained scans of an early German language Pittler catalogue from 1894 which featured many types of B & C lathe not exported to the UK. The translated pages mention Whitworth threads quite a few times  so we have to wonder if they were using them for their full production as well as for the UK. 

below top: The spindle for the B2 number 1253 showing the three lugs that locate in the gear or worm, (left) the adjustable bearing (centre) and the pulley/back gear drum. 

second photo below:  another spindle from the earlier Invention factory production and shows the left/hand bearing, this is keyed to the mandrel and thus turns with it, it is adjusted via two locknuts to take up any wear. The bearing shells that they fit in to are located in the headstock casting and require oil drip feeds as do many old lathes using this type of bearing.  The spindle is bored 13/32 inch and is fitted with a removeable bush to take 8mm collets, chucks etc.  The reason it's removeable is to permit thicker lengths of rod to pass through when making batches of screws etc using a capstan tool post. Although the mandrel threads are the same these two spindles have minor differences and are not interchangeable although many other parts of the lathe spanning several years will interchange perfectly