Abstract: Disclosed is an electric discharge machining method in which the electric discharge working gap between an electrode and a work piece to be machined is automatically adjusted. To detect the condition of the discharge working gap, a low voltage pulse is applied each time a plurality of high voltage pulse for electric discharge machining are applied for a predetermined time. The working current resulting from the application of each low voltage pulse is detected to control the feeding of the electrode and thereby to automatically adjust the discharge working gap to a predetermined value.

Abstract: There is disclosed a method for giving by electrical discharge machining a uniform satin finish to the roll surface of a work in roll form in a short period of time. To prevent the occurrence of any streaky pattern on the satin finish work surface, a plurality of divided electrodes, which are divided and arranged at predetermined spaces, are each fed traversely a distance corresponding to the electrode mounting pitch while maintaining the predetermined spacing between the electrodes. To improve the working efficiency, a plurality of rows of divided electrodes are provided, and by virtue of this improved working efficiency, the required satinizing electrical discharge machining of two or four rolls for use on a rolling mill can be completed within the life time of the satinized rolls being used on the rolling mill.

Abstract: There is disclosed an apparatus for giving a satin finish to the surface of a crowned roll. A plurality of electrode heads are divided and arranged along the axis of rotation of the crowned roll to be worked, and one or a plurality of rectangular electrodes are mounted at a predetermined spacing on each of the electrode heads. The discharge gap of each rectangular electrode is controlled by a servomechanism at a predetermined value and it is also fed traversely a predetermined distance by a traverse feed mechanism. The electrode is rectractably mounted on the electrode head and it is fixed in position so that the discharge surface of the electrode is projected into contact with the roll surface of the crowned roll. The discharge electrode surface of each rectangular electrode is initially flat and this discharge surface is consumed to conform with the shape or contour of the roll surface upon initiation of discharge.

Abstract: Disclosed is a process for subjecting the outer surface of a satinizing roll to electrical discharge machining to produce, on the roll surface, a satin-like roughened surface with a uniform roughness. With the electrical discharge machining process, a plurality of electrodes of the same shape are mounted at equal pitches on each of a plurality of head columns, and the head columns are repeatedly reciprocally fed traversely along the axis of rotation of a roll over a predetermined distance which does not cause any stepped portions on the roll surface to effect the electrical discharge machining. The feeding of the electrodes toward the surface of the roll is separately controlled for each head column. To obtain the optimum working results, the head columns are repeatedly reciprocally fed traversely over a distance equal to the electrode mounting pitch.

Abstract: Disclosed are a process and apparatus for electrical discharge machining of the outer surface of a satinizing roll to produce a satin-like roughened surface of a uniform roughness. This electrical discharge machining process produces a uniform satin-like roughened surface on the outer surface at each end of the roll, and for this purpose the process involves a step of decreasing the discharge current in proportion to decrease in the area which is to be worked by an electrode located at the roll end and thereby maintaining the flow of current per unit area at a constant value. The apparatus for performing the process comprises position detecting-means for detecting that the electrode has been moved to the roll end, and means responsive to the output signal of the position detecting means to control the off-time of current pulse which causes a discharge between the electrode and the roll.

Abstract: There is disclosed an electric discharge machining method in which the discharge working gap between an electrode and a work piece is automatically adjusted to prevent the occurrence of a streaky pattern in the surface of the work piece due to variation in the amount of machining. After a plurality of high voltage pulses have been applied for a predetermined time across the working gap, a low voltage pulse is applied across the working gap. In response to the application of the low voltage pulse, the feeding of the electrode is controlled by a pulse motor in a direction to reduce the working gap, and as soon as the discharge is started the feed control is stopped and the discharge machining is then effected in response to the application of high voltage pulses.

Abstract: Disclosed are a process and apparatus for subjecting the outer surface of a satinizing roll to electrical discharge machining to produce a satin-like roughened surface of a uniform roughness. With this electrical discharge machining process, the electrical discharge machining speed of a plurality of electrodes mounted on a plurality of head columns is held lower than a steady state working speed until the electrodes on all the head columns start discharging, and in response to the detection of the discharge of every electrode on the head columns the working speed is changed to the steady state working speed and the head columns are simultaneously moved traversely along the axis of rotation of a cylindrical work, thus preventing the occurrence of a difference in the depth of erosion or stepped portions on the surface of the work during the initial working period.