Abstract: In a method of producing crankshafts in a mass-production line, after a crankshaft casting is ground to its specified geometry, it is measured to detect a dynamic imbalance. Then, at least one radial balancing bore is drilled in a specified counterweight to a depth according to a resultant imbalance so as to balance the crankshaft if the crankshaft is judged, based on the resultant imbalance, to fall within a region in which a dynamic imbalance is eliminated by drilling bores. Otherwise, the crank shaft is removed out of the mass-production line if it is judged to be out of the region.