Abstract: A CNC machine tool deflection compensation system integrated in a CNC machine tool Controller for providing continuous, accurate, real-time compensation for unintended and/or undesired X, Y and/or Z-axis coordinate deflections from a preprogrammed path of tool movement in an X, Y-axis coordinate plane, and methods for carrying out same, so as to ensure that the tool remains precisely on its programmed path irrespective of such deflections. Such undesirable deflections result inherently from, for example: i) changes in tool dimensions; ii) changes in the acute included angle ? of the tool between its axis and the initial vertical Z-axis coordinate; iii) changes in the rotational angle ? of the tool about the Z-axis coordinate; and/or iv), the location of the tool in the X,Y coordinate plane.