Abstract: An apparatus for locating the geometrical center of symmetrically shaped bore (3) in a material (2) includes a detector (4) distinguishably responsive to a property of the material (2), bore traversing means (6, 9, 10, 11) for moving the detector (4) adjacent the material (2) and along a predetermined raster scan path, and control means (15, 16, 17) responsive to changes in electrical signal outputs of the detector (4) as the traversing means (6, 9, 10 11) is scanned across the bore (3) in two mutually orthogonal directions. The control means is operative to monitor the coordinates of the interceptions of each of two mutually perpendicular chords across the bore (3) with an edge of the material (2), and to calculate the coordinates of the center of the bore (3) from these. Preferably the apparatus includes an eddy current detector (4) for determining the position of a bore (3) and an ultrasonic detector (5) for inspecting the material (2) around the bore ( 3) for flaws.