GB1363846A - Electrlytic drilling of branches from passages - Google Patents

Abstract

1363846 Electrolytic machining of passages DEFENCE SECRETARY OF STATE FOR 26 Aug 1971[27 Aug 1970] 41357/70 Heading C7B A lateral branch 16 is electrolytically drilled from a passage 4 in a metal workpiece using as tool a tube 8 of insulating material which contains a wire electrode 12, is formed with one or more holes in its sidewall, and which makes a clearance fit in the passage 4, whilst supplying electrolyte to the bore of the tube under pressure such that a jet of electrolyte emerges from the hole(s) in the tube and impinges on the passage wall. The tube forming the body of the tool may be of fused quartz; and the electrode 12 may be formed by a wire or by a gold deposit on the internal wall of the tube. To limit variation in current intensity during operation the wire electrode may terminate short of the highest hole in the tube, the wire electrode may be coated with insulation (50) in the neighbourhood of the holes Fig. 4 (not shown) or the tool may traverse the passage laterally during operation towards the passages being formed. To concentrate electrolyte flow, the holes may be lined with capillary glass tubes which extend outwardly from the tool tube 8 Fig. 5 (not shown). In the production of turbine blades the present method may be used to provide lateral passages to connect cooling passages running adjacent the leading edge of the blades. In the tool used therefore the holes may be formed in a partial helix about the tube; and the tool may be positioned in operation such that the lateral passages formed do not lie on a plane through the axes of the cooling passages connected thereby Fig. 6 (not shown) thus imparting a swirling motion to cooling air subsequently passed therethrough. The tool and workpiece may be mounted in a jig provided with means for producing relative movement between the tool and the workpiece in both lateral and axial directions, and to provide rotation of the workpiece, Fig. 1 (not shown).