1. A process for the electrochemical machining of an electrochemically machinable conductive metallic workpiece comprising the steps of: SPACEDLY JUXTAPOSING SAID WORKPIECE WITH AN ELECTROCHEMICALMACHINING ELECTRODE HAVING A SUPPORTING SHANK PORTION AND A MACHINING FACE PORTION TO FORM A MACHINING GAP; PROVIDING AN AQUEOUS-ELECTROLYTE COOLANT FLOW THROUGH SAID GAP; PASSING AN ELECTRICAL CURRENT ACROSS SAID GAP; PROVIDING RELATIVE MOVEMENT BETWEEN SAID ELECTRODE AND SAID WORKPIECE TO MACHINE ELECTROLYTICALLY A CAVITY IN SAID WORKPIECE; SHIELDING THE WALLS OF SAID CAVITY PROXIMATE SAID SHANK PORTION OF SAID ELECTRODE BY FORMING IN SITU IN THE COURSE OF THE ELECTROLYTIC MACHINING OF SAID CAVITY A SHEATH OF AN ELECTRICALLY INSULATING MATERIAL TO LIMIT FURTHER ELECTROLYTIC ACTION BY INTRODUCING A SUBSTANCE INTO SAID ELECTROLYTE COOLANT CAPABLE OF FORMING SAID SHEATH; AND PREVENTING FORMATION OF SAID INSULATING SHEATH ON SAID WORKPIECE PROXIMATE SAID MACHINING FACE PORTION OF SAID ELECTRODE BY PROVIDING PERIODIC SPARK DISCHARGE BETWEEN SAID ELECTRODE MACHINING FACE PORTION AND SAID WORKPIECE.