Abstract: Disclosure is made of a bar-clamping device having a hollow spindle carrying first and second collets, each provided with a closing drive ensuring independent axial motion of one of the collets relative to the other. The closing drives of each collet are installed in the spindle and designed so that the axial efforts produced during clamping of a bar are directed in the opposite directions.

Abstract: An apparatus for electroerosive piercing of holes in workpieces having an electrode tool in the form of a rod placed with a clearance in a shell and projecting therefrom, a device for feeding and rotating the rod mechanically connected to a device for reciprocating the shell relative to the rod. The device for reciprocating the shell relative to the rod is fashioned as a hydraulic cylinder, a piston of which has the shell rigidly secured thereto at the side of the workpiece, and at least one cavity of the hydrauylic cylinder is connected to a system for feeding and discharging a working fluid, the piston having at least one passage communicable with the interior of the shell of the electrode tool and wherethrough the rod of the electrode tool extends with a clearance.

Abstract: A device for electrode-tool feed control in electroerosion machines includes a power source (1) equipped with reservoir capacitors, one output of the power source (1) is connected to a workpiece (2) and the other to the electrode-tool (3), a threshold circuit (4), and one of the inputs of a switching device (5). The output of the threshold circuit (4) is connected to an electronic switch (6) and to the second input of the switching device (5) whose output is connected to an amplifier (7). The output of the amplifier (7) is connected to a diode bridge (8) of a converter unit (9), connected in series with a primary winding (10) of a transformer (11) of this converter unit (9) and to an AC supply line (12). The output of the electronic switch (6) is connected to the other diode bridge (13) of the converter unit (9) and to a second primary winding (14) of the transformer ( 11) of this converter unit (9).

Abstract: A device for electrical discharge piercing of holes in components comprises a tool electrode mounted in an electrode holder (18) and made as a rod (26) enclosed, with a clearance, in a sheath (27) and somewhat projecting therefrom, and a contrivance for traversing, locking and wear compensation of the tool electrode.

Abstract: An electrode tool for electroerosive drilling of holes in workpieces includes a central electrode fabricated from an electroconductive material and disposed in a shell with a gap. The central electrode projects from a working end of the shell toward the workpiece, the projecting portion of the central electrode being bent at an angle .alpha., the end of the bent portion being spaced from the side surface of the shell. A method for electroerosive drilling of holes having variable transverse and longitudinal sections in terms of hole depth, this method also being capable of producing holes with reverse angles and obtaining round shaped configurations of holes.