Electro-abrasive polishing of the inner surface of pipes to extra-smooth mirror finish

An electro-abrasive polishing process of the inner surface of a small-diameter pipe to an extra-smooth mirror finish which comprises:

• a preliminary-polishing process in which the roughness of the inner surface of the small-diameter pipe is reduced to at least 0.5 .mu.m Rmax or under by electroabrasive polishing process of the inner surface of the small-diameter pipe by inserting a preliminary-polishing tool electrode comprising a core electrode wrapped with a non-woven nylon sheet comprising abrasive grains in the small-diameter pipe to be polished and passing a small amount of current through the electrolyte between the small-diameter pipe that serves as the anode and the tool electrode that serves as the cathode and, at the same time, by mechanically polishing the inner surface of the small-diameter pipe by rotating the tool electrode and axially reciprocating it or the small-diameter pipe relative to each other;
• and
• a subsequent mirror finishing process in which the inner surface of the small-diameter pipe is polished to a mirror finish by electro-abrasive polishing process of the inner surface of the small-diameter pipe by inserting a mirror-finishing tool electrode comprising a core electrode wrapped with an urethane sheet in the small-diameter pipe to be polished and passing a small amount of current through the electrolyte containing free fine abrasive grains between the small-diameter pipe that serves as the anode and the tool electrolde that serves as the cathode and, at the same time, by mechanically polishing the inner surface of the small-diameter pipe by rotating the tool electrode and axially reciprocating it or the small-diameter pipe relative to each other, in conjunction with the action of the free fine grains contained in the electrolyte.