4 has its greatest reach in the height direction h is referred to as the blade segment 39 s maximum height h max the height value at which the blade segment begins at the bottom thereof is referred to as the minimum height h min the span in the height direction between the minimum height h min and the maximum height h max is the overall height h max of the blade segment the second blade section lateral surface 6 extends apart from manufacturing tolerances in a plane spanned by the longitudinal direction z and the height direction h the first blade segment lateral surface 5 is made up of a first portion 10 located higher up on the blade segment 4 further away from the foot segment 1 and a second portion 11 located lower down on the blade segment nearer the foot segment 1 as already explained earlier the comparatively flat rounded transition area 9 between the foot segment 1 and the blade segment 4 is not part of the blade segment 4 the first portion 10 is practically parallel to the plane defined by the longitudinal direction z and the height direction h accordingly it is also parallel to the second blade segment lateral surface 6 i e its gradient is infinitely large the first portion 10 may alternatively enclose a small angle not exceeding 2 u00b0 with the height direction h i e dh db assumes a finite value and except for manufacturing tolerances run parallel to the longitudinal direction z the second portion 11 is also parallel to the longitudinal direction z except for manufacturing tolerances but compared with the first portion 10 encloses a substantially larger angle of 8 u00b0 to 12 u00b0 with the height direction h in other words the first portion.