A work method for a Cartesian machine tool includes the following steps

starting machining of a workpiece;

carrying out a machining cycle; and

carrying out a qualification operation, i.e., an operation to check a relative positioning system, on board the machine tool, by way of comparison with a positioning system with absolute reference for calibration, which is adapted to check the displacement of the indications of the positioning systems on board the machine, i.e., of the relative reference system, with respect to the positions of an absolute reference system for calibration. The method further includes the steps of

checking the outcome of the qualification operation,

If the qualification operation is passed successfully, then proceed with an operation to measure the workpiece prior to finishing.

If the qualification is not passed, then proceed with a compensation step, which includes one or more compensation operations.