The thin-walled seat on the shrink disk seat (f seat) often gets a smeared / rattled surface when it is turned. Sanding the seat can fix this. The seat can only be ground if there is an undercut on the shaft shoulder instead of the radius.On the series machines, it is not possible to profile the grinding wheel so that the radius can also be ground.The measuring probe in the machine cannot be used with the larger sizes (ST77 and KT97) if the seat is rotated. A measured value comparison iscarried out on the lower seat and all other values are adjusted to this. If the f-seat is rotated, the button does not come to the WDR seat and no compensation can be made.This change does not result in any additional costs.