Apparatus for machine tool feedrate override using limiting parameters corresponding to actual spindle speed

A machine tool comprising:

• a machine base;
• a workpiece holder supported by the machine base;
• at least one spindle to which at least one cutting tool is fixedly secured;
• a plurality of servo motors;
• at least one spindle motor capable of rotating the at least one spindle;
• a computer numerical control (CNC) capable of directing the operation of the servo motors to control movement of the workpiece relative to the cutting tool;
• the CNC further capable of directing the operation of the spindle motor to control a current spindle rotational speed;
• and
• a feedrate control apparatus for controlling a feedrate of the workpiece relative to the cutting tool, the apparatus capable of receiving spindle parameter data, the spindle parameter data comprising first and second pluralities of spindle parameter limits and first and second pluralities of corresponding spindle rotational speeds such that different spindle parameters have different spindle rotational speeds, wherein the feedrate control apparatus is further capable of receiving first and second current spindle values;
• wherein the apparatus is further configured to compare the first current spindle value to a respective first spindle parameter limit having a corresponding first spindle rotational speed that has a predefined relationship to the current spindle rotational speed, wherein the apparatus is also configured to compare the second current spindle value to a respective one of the second spindle parameter limits having a corresponding second spindle rotational speed that has a predefined relationship to the current spindle rotational speed;
• wherein the apparatus is further configured to adjust the feedrate of the machine tool based on the comparison between at least one of:
• (i) the first current spindle value and the respective first spindle parameter limit and (ii) the second current spindle value and the respective second spindle parameter limit.