Carborundum (Silicon Carbide) was developed for the mining and well drilling industry. It is designed to wear through the toughest materials.
As such, it can be used to smooth out pitted bearing surfaces.
However, most bearing surfaces are surface hardened through use. The constant pressure of the bearings on the cups and cones eventually hardens the contact surfaces. Carborundum cuts through that hardened surface exposing less hard material.
If the cups and cones were cheap to begin with, they may not be hardened throughout and the carborundum will cut away whatever hardening there was.
If the cups and cones were made of hard material throughout, and ground for smoothness (as on classic dura-ace) then carborundum will work just fine.
If there is no pitting, there is no reason to use it. If there is pitting, I don't know of any other solution.
Amir "Illegitimi non carborundum" Avitzur Ramat-Gan, Israel
selling classic parts on ebay at:
http://ebay.com/