Abstract: A method of electrochemically machining a workpiece made of electrically conductive material so as to provide a radius on an edge of the workpiece comprises, (a) providing a cathodic tool comprising a cathode section sandwiched between two anode sections and separated therefrom by insulation, (b) locating the tool adjacent to but separate from the workpiece so that the cathode section is positioned centrally over the edge of the workpiece to be radiused and the anode sections lie facing opposite sides of the edge, (c) causing electrolyte to flow between the tool and the workpiece, (d) applying a cathodic voltage to the cathode section, (e) applying preselected anodic voltages simultaneously to the workpiece and the anode sections so that electrical field null points between the cathodic tool and the workpiece lie either side of the edge to be radiused, and (f) varying the electrical field between the tool and the workpiece so as to cause the null points in the electrical field to move with respect to each oth

Abstract: A turbine suitable for a gas turbine engine is provided with a stage of rotary aerofoil blades which is surrounded by a shroud ring made of silicon nitride. In order to minimize load transfer between the shroud ring and the turbine casing the shroud ring is radially supported by and radially spaced apart from the turbine casing by an annular brush seal.

Abstract: The production of passages in workpieces is described by an electrical method which simultaneously utilizes electrochemical and electrical discharge machining with a single electrode and dilute electrolytes. The method overcomes the metallurgical defects inherent in the recast layer left by electrical discharge machining which is removed by electrochemical machining. The method is particularly suited to producing cooling passages in the turbine blades of gas turbine engines and can be used to produce venturi shaped holes with rounded edges.