An electrochemical machining process for forming a non-circular hole from a substantially circular hole within a workpiece using an electrode. The electrode is made of an electrically conductive material and has insulated areas in which the electrically conductive material is coated with an insulating material, and exposed areas of metal or conductive material. The insulated areas and exposed areas extending in rows substantially along a longitudinal axis of the electrode. The electrode is first positioned in a substantially circular hole. An electric current is then applied to the electrode to electrochemically remove a predetermined amount of material from the substantially circular hole to form a non-circular hole. A variety of different non-circular shapes are achievable using the process.