For several years i have owned a Boley 5LZ lathe . This is a very high class lathe and is a pleasure to use . The headstock is belt driven as it was thought better than a gear drive for high quality surface finish .
The drive to the side shaft is also belt drive to make the sliding and surfacing feeds as smooth as possible
The main drive belt needed changing and this is quite an involved job .
The headstock pulley is supported on a separate set of bearings to the headstock main shaft to eliminate any side loading from the tension of the drive belt distorting the headstock shaft
The headstock pulley is on roller bearings and the headstock is on tapered hardened bronze bearings
To change the drive belt the headstock shaft is removed then the drive pulleys ,the lead screw is centrally mounted so as not to give any side loading to the carriage it is also totally enclosed and this has to be removed as well
This takes about 4 hours to do and about the same to rebuild
It is now all back up and running ,There is a write up on this lathe
http://www.lathes.co.uk/boley5lz/