This innovative machinery allows to carry out machining without having to disassemble the shaft from the lower case of the turbine and without disassembling the power transmission flanges between the generator and the user. The particular construction mechanics adopted, which does not use the same shaft surface as a reference for turning, allows the operator to set in advance the type of grinding process to be performed, and therefore obtain the desired result and with the required precision without dragging any defects already present on the shaft surface.