No. We repair spindles only with antifriction bearings. Normally these bearings are angular contact ball bearings or double row cylindrical roller bearings with taper bore.
Yes. We have converted many hydrodynamic spindles in antifriction bearing spindles. However, feasibility study needs to be carried out before taking such decision.
Every VMC/HMC machine has test chart in the manual. We try to achieve values given by machine tool manufacturer. Normally, we achieve less than 3 micron run out at taper bore and less than 20 microns at 300 mm away from taper bore on checking mandrel.