In considering errors due to elastic deformations in milling, the workpiece-work-holding fixture assembly is generally considered to be infinitely rigid, at least when the geometrical features so permit. The tool-tool-holder-spindle assembly and the machine axes are then deformed under the action of the cutting forces. This deformation leads to a positioning defect of the tool in relation to the theoretical position. With the aim of taking this positioning defect into account in manufacturing, a ‘Virtual Worker’ was implemented that was capable of predicting this defect, in relation to the type of machining, and of compensating for it. It was built on a set of data blocks drawn up for each tool. In order to fill in these tool data blocks quickly, a master workpiece was elaborated that brought together the milling operation characteristics for the tool's behaviour at work. By milling and then measuring this master workpiece, the behaviour of the tool-tool-holder-spindle assembly was able to be fully characterized at work.