This paper presents mechanisms studies of micro scale milling operation focusing on micro cutter edge radius. To address this issue, the tool wear model is developed in the present work. Starting with an analysis of the milling edge radius of the tool, the influence of the downscaling on the edge radius is determined by analyzing the milling force. This simulation is used to predict the extent of tool wear in the same milling operation condition by increasing of the tool edge radius. This model accurately predicted the increasing of force with tool wear progress and provides the means for further study of the micro milling tool wear.