A printhead assembly includes an elongate extrusion defining a plurality of longitudinally extending ink channels. One method of planarizing a microelectronic substrate assembly in accordance with the invention includes pressing a substrate assembly against a planarizing surface of a polishing pad at a padsubstrate interface defined by a surface area of the substrate assembly contacting the planarizing surface. The second bore axis includes an angle of approximately 90\xb0 with a plane defined by the first bore axis and the longitudinal axis of the rod.