So that the neck is cylindrical (with a cone within the limits provided for by technical conditions), abrasive circles with longitudinal movement of the carriage should move parallel to the axis of the crankshaft. This condition can be fulfilled with permissible approximation if the carriage is moved parallel to the upper base surface of the 26 foundation frame and its side surface 27. For this, racks 16, which have a height that ensures the free passage of the crank of the processed shaft under the carriage, is treated with accuracy that provides their same height within the landing of planting from.
