CNC Mill Spindle: Bearings, Belt Drive, VFD, ATC, and ... CNCCookbook
A Mazak QT20 lathe runs 120mm ID bearings on the spindle and has a spindle bore of ″. That works out to a wall thickness of about ″ or about 29mm. Now let's say we want to build a lathe spindle with a spindle bore of 2″. Let's give it a 1″ wall thickness, so we need bearings with 4″ ID which is 101mm.