One major problem encountered in NC machining is that cutting load fluctuates in twisty tool paths and increases momentarily when milling concave corners where stock material concentrates. Much research has been conducted on controlling milling forces but the problem remains unsolved. This paper presents a solution to reduce and stabilise cutting load in NC milling operation by applying computational techniques to isolate the concave corners of a machining region, thereby forming a major region and a number of disjoint sub-regions. Due to the suppression of concave corners, the boundary profile of the major region will become smoother. Contour-parallel offset tool paths can then be used to remove the material in the major region. For the isolated sub-regions, special corner removing tool paths with the use of different cutter sizes will be employed. By using this approach, the adverse effects caused by excessive undulation of milling tool path can be reduced.