Abstract: Electrical discharge apparatus for producing on the surface of an electrically conductive workpiece a textured or matt finish comprises a plurality of electrodes each connectable to an electrical power source and each carried by a head which in use of the apparatus can be moved linearly of the workpiece with the electrodes each spaced at a predetermined distance from the workpiece surface. A characteristics of the voltage conditions present within the gap existing between the electrodes and the workpiece surface is monitored and, the head is moved towards and away from the workpiece surface to maintain the monitored characteristic within predetermined limits. Dielectric fluid is retained within the gap existing between the electrodes and the workpiece surface, and a series of discrete electrical discharges is promoted between each electrode and the adjacent workpiece surface to cause particles to be removed from the workpiece surface and produce a textured or matt finish thereto.

Abstract: The invention concerns apparatus for inspecting the flat surfaces of a metal billet and includes a carriage mounted scanning head having a high frequency eddy-current probe (21) mounted on the periphery of a disc (18) rotatable above the billet surface about an axis perpendicular to said surface. The carriage (1) is located in abroad of the rotating scanning head. The eddy-current probe is connected to transmit electrical signals representative of the condition of the billet surface under inspection to signal processing equipment remote from the apparatus.

Abstract: Inspection equipment for detecting defects in the surface of steel billets or other elongate members includes high-frequency energized eddy-current surface scanning probe which transmits signals representative of the surface condition and the probe surface spacing to a dual-channel receiver.The signals from both channels of the receiver are combined to provide outputs representative of the surface condition compensating for changes in sensitivity resulting from changes in the probe spacing during scanning.Probes may be positioned above the plane surfaces and/or the corners of the billet. The latter being positively located through rollers which bear against the two sides of the billet which flank the edge under inspection.