biasing the probe 32 out of alignment with the reference axis 15 so that the distal end of the probe 32 will readily contact the inside surface of selected bearing seats 36 in the preferred embodiment the visual readout means 46 is a simple dial 26 and needle 27 gauge calibrated in units convenient to machinists in practice the device is installed in the main bearing seats of an engine block 40 with the slidable collar 22 being disposed between the two bearing means 12 and 13 the collar 22 is slid along the shaft 11 until the distal end 48 of the probe 32 is adjacent a selected bearing seat 36 the set screw 23 is tightened locking the collar 22 to the shaft 11 the distal end 48 of the probe 32 is contacted to the interior surface of the selected bearing seat 36 and the threaded sleeve 31 is tightened to maintain the orientation of the radial distance indicator mechanism 24 with respect to the reference axis 15 the shaft 11 is rotated thereby moving the distal end 48 of the probe 32 around the interior surface of the selected bearing seat 36 variations in the distance from a point in the interior surface of the selected bearing seat 36 to the geometric foot of that point in the reference axis 15 cause the distal end 48 of the probe 32 to move radially in.