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Thermal growth of spindle and other components is common in CNC machines, especially with MQL machining, and directly impacts positioning accuracy and thereby quality. A common method to address this is by measuring the thermal growth using gage bore probing and then compensating for it. Application of this method in 5-axis CNC machines is relatively new and effectiveness is often not tested. Error sources due to various orientations of the part could arise. A new artifact based method is presented for assessment of thermal compensation used by the CNC OEM. The method involves an artifact, test cycle and automated data logging. A precision granite artifact with gage bores on different faces is fabricated and can be presented for probing in different orientations. The machine is warmed up using repeated dry-cycling, thereby creating thermal growth. Compensation error is evaluated as the difference of actual thermal growth and compensation offset.