In order to machine parts or to completely machine complex workpieces, at least one, preferably two, machine tools (1, 2) are provided which each comprise a base body (3, 4) and machine units (7, 8) that can be displaced thereupon in a horizontal direction. Each machine unit has a work spindle (13, 14) which is held in a crankshaft-like support (11, 12) such that it can be displaced in an axial direction of the spindle. The support is pivotally mounted and holds each work spindle over a respective transport system (31, 32) for a part or for the workpieces (37, 38). Machining devices which are provided in the form, for example, of a tool support (44) for turning, boring and/or milling tools, of a laser welding device (46), of a grinding device (47), of a brush device (48), and of an assembling device are provided in the functional area of one of said machine tools.