Arrangement for electrospark working of internal conical surfaces of metal parts

In an arrangement for the electrospark erosive working of internal conical surfaces of metal workpieces having a hollow space with a high slenderness ratio, the hollow space being bounded by a cylindrical surface terminating in a conical surface coaxial therewith, the arrangement having an electrode for performing the working, a source of burning electrical impulses, means connecting said electrode to a first pole of such electrical source, the electrode terminating in a conical burning part and being provided with a shaft insulated from the workpiece, guiding means for the shaft of the electrode provided in the hollow cylindrical surface bounding the hollow space of the workpiece, means connecting the workpiece to the second pole of the source of burning electrical impulses, means for rotating the electrode, and means providing for a quick and a microadvance of the electrode relative to the workpiece, the improvement which comprises a holder, a first, hydraulic working cylinder, a second, hydraulic cylinder for a quick advance, and a third, hydraulic cylinder for the microadvance of the electrode, said second and third hydraulic cylinders being supported by the holder, conduit means interconnecting all of said hydraulic cylinders, a supporting piston slidably arranged in the first, hydraulic working cylinder, the electrode resting against this supporting piston, a second piston slidably arranged in the second hydraulic cylinder, a first drive for the quick advance, a third piston slidably arranged in the third hydraulic cylinder, a second drive for the microadvance, compression springs provided in both cylinders for quick and microadvance, and a tension spring provided in the first, hydraulic working cylinder.