Positioning drive, in particular for a machine tool

A positioning drive, comprising a hydraulic motor (10) which has a cam disk (17) which is rotatable with a motor shaft (18) and is provided with a cam (19), a control valve (12) with which the hydraulic motor (10) forms a structural unit with a housing (37, 46) and has a valve piston (15) which is displaceable between several positions, a control element (16) via which the valve piston (15) can rest against the cam disk (17), and an adjustment element (65) which is operatively arranged between the control element (16) and the valve piston (15) and coaxial to the valve piston (15), and wherein by relative displacement of said adjustment element with respect to the valve piston (15), the relative position between said valve piston (15) and said control element (16) is variable and the position of said adjustment element with respect to the valve piston (15) secured by a releasable locking element (72, 80), and wherein an outer part of the two parts, valve piston (15) and adjustment element (65), is guided outwardly through the housing (46), and the locking element (72, 80) is accessible from outside the housing (46).