A method of manufacturing a rotary cutting tool is described. The rotary cutting tool defines a central longitudinal axis and includes a shank portion and a cutting portion adjoining the shank portion. The shank portion has a shank end and the cutting portion has a cutting end opposite the shank end. One or more blades are separated by a flute. A main, internal coolant passage extends from the shank end, through the shank portion, and into the cutting portion. The method includes forming at least one secondary coolant passage in fluid communication with the main, internal coolant passage in which the at least one secondary coolant passage is formed by using electro-magnetic radiation.