Process where a controlled spark discharges from an electrically charged, threaded electrodes create a threaded hole. Beskrivning The process The tool consists of a threaded pin [1] which at the starts of the process is at the bottom of a pre-machined hole in the workpiece. Connection via power supply makes the pin act as the cathode and workpiece as the anode. When the pin is near the hole wall, intermittent spark discharges occur, which means that the workpiece is melted and vaporized. The discharge is supported by a dielectric liquid [2], which also helps to cool the process and carry away the removed material. The stud is not rotated about its own axis but in a rotating path of gradually increasing diameter. This diameter is increased until the desired thread is reached. The spark gap [3] leads to the machined contour to be slightly larger than the tap contour. This applies to so-called orbital processing. There are other variants that do not require a pre-machined hole. Typiska applikationer Metoden används för hårdare metalliska material där konventionell gängning ej är applicerbar. Electrical discharge threading Process films Advantages and disadvantages In comparison with alternative methods Deep holes with only a thin wall at the bottom of the hole can be created without the material cracking or deformation. By direct electrical discharge threading holes are drilled and tapped in a single operation.
