Method for manufacturing a screw rotor for a compressor, a blower, a vacuum pump or an expander, that at least comprises the following operations: - the clamping of a workpiece in a grinding machine to perform a grinding operation; - the performance of one or more cylindrical grinding operations, whereby in such cylindrical grinding with a cylindrical grinding disk, one or more sections of the workpiece are ground to the desired diameter to form a rotor shaft section; - the performance of one more profile grinding operations, whereby in such profile grinding with a profile grinding disk, a section of the workpiece is profiled to form a rotor body of the screw rotor; whereby during the manufacture of the screw rotor in the grinding machine, the workpiece is not unclamped and both the cylindrical grinding operations and the profile grinding operations are executed with the same grinding machine; whereby the clamping of the workpiece comprises the steps of making a centre hole in each of the two ends (15,16) of the workpiece and clamping the workpiece in between two centre points of the grinding machine; characterized in that after clamping the workpiece between both centre points, a cylindrical grinding operation is performed that consists of cylindrically grinding a section, on at least one end of the workpiece, to obtain a cylindrical clamping surface that is centred with respect to the centre line (GG'); whereby an additional cylindrical grinding operation consists of additionally clamping the workpiece with a clamping mechanism or clamping system to the clamping surface and cylindrically grinding a section at the other end of the workpiece to form a cylindrical support surface that is centred with respect to the centre line (GG'); whereby, in order to perform a profile grinding operation, the workpiece is clamped at one end to the clamping surface using a clamping mechanism or clamping system and is supported in a rotating way at the other end by a stay that is affixed around the aforementioned support surface; whereby after a first coarse profile grinding operation to obtain a workpiece with a coarsely ground rotor body, one or more interim cylindrical grinding operations are performed to grind one or more rotor shaft sections, the external diameter of the rotor body and/or one or both end faces (4,5) of the rotor body, after which the profile of the rotor body is finely ground during a fine profile grinding operation; and whereby during the cylindrical grinding and the profile grinding, the workpiece is driven at one end, and for clamping the workpiece in the grinding machine at the other not directly driven end of the workpiece, a live centre point is used that engages in a centre hole in the end of the workpiece concerned. - the clamping of a workpiece in a grinding machine to perform a grinding operation; - the performance of one or more cylindrical grinding operations, whereby in such cylindrical grinding with a cylindrical grinding disk, one or more sections of the workpiece are ground to the desired diameter to form a rotor shaft section; - the performance of one more profile grinding operations, whereby in such profile grinding with a profile grinding disk, a section of the workpiece is profiled to form a rotor body of the screw rotor; whereby during the manufacture of the screw rotor in the grinding machine, the workpiece is not unclamped and both the cylindrical grinding operations and the profile grinding operations are executed with the same grinding machine; whereby the clamping of the workpiece comprises the steps of making a centre hole in each of the two ends (15,16) of the workpiece and clamping the workpiece in between two centre points of the grinding machine; characterized in that after clamping the workpiece between both centre points, a cylindrical grinding operation is performed that consists of cylindrically grinding a section, on at least one end of the workpiece, to obtain a cylindrical clamping surface that is centred with respect to the centre line (GG'); whereby an additional cylindrical grinding operation consists of additionally clamping the workpiece with a clamping mechanism or clamping system to the clamping surface and cylindrically grinding a section at the other end of the workpiece to form a cylindrical support surface that is centred with respect to the centre line (GG'); whereby, in order to perform a profile grinding operation, the workpiece is clamped at one end to the clamping surface using a clamping mechanism or clamping system and is supported in a rotating way at the other end by a stay that is affixed around the aforementioned support surface; whereby after a first coarse profile grinding operation to obtain a workpiece with a coarsely ground rotor body, one or more interim cylindrical grinding operations are performed to grind one or more rotor shaft sections, the external diameter of the rotor body and/or one or both end faces (4,5) of the rotor body, after which the profile of the rotor body is finely ground during a fine profile grinding operation; and whereby during the cylindrical grinding and the profile grinding, the workpiece is driven at one end, and for clamping the workpiece in the grinding machine at the other not directly driven end of the workpiece, a live centre point is used that engages in a centre hole in the end of the workpiece concerned.