The relationship between the working gap width and the machining condition was investigated in Electro-chemical Machining using sodium nitrate solution, and the working gap width in machining using sodium nitrate solution was compared with it in machining using sodium chloride solution. The results are as follows.
(1) The relationship between the working gap width and the machining condition using sodium nitrate solution is given by the some relationship that has feed rate increase in machining using sodium chloride solution.
(2) The working gap width can be estimated numerically by using the experimental relationship between the feed rate and the current density.
(3) The working gap width in machining using sodium nitrate solution becomes narrower than that in machining using sodium chloride solution under the some machining condition on supply voltage, feed rate of electrode, and specific conductivity.
(4) The working gap width in machining without feeding the electrode approaches to the steady gap width with machining time.
(5) At the lower current density, dissolution of the work-piece does not proceed in machining with feeding electrode and without feeding electrode.