Method of making a window in a tubular using an expandable watermelon mill

A watermelon mill has a smaller dimension for run in and a larger one for reaming out the window made by a window mill and passes through a smaller drift and then gets larger for more effective widening of the window. The cutters are preferably tungsten carbide or polycrystalline diamond inserts and they are mounted to blades that are ramped outwardly by a cone upon relative movement between the two. The body can be in multiple pieces that are rotationally locked and movable relative to each other longitudinally. Actuation to the larger dimension can be by setting down weight or by fluid pressure with the dimension getting smaller as a return spring allows the cutters to retract upon removal of applied pressure.