Drillability of zinc/graphite metal matrix composites

The paper reports the results of a series of drilling tests undertaken on zinc alloy(ZA-27) based composites reinforced with graphite particles. The graphite content in the zinc alloy was varied from 1 to 5% in steps of 2% by weight. The composites were fabricated by the vertex method in which a vortex was created in the molten metal through a rotating impeller. A radial drilling machine was used for the test and a digital tool post dynamometer was used to record the various forces involved. Holes of dia-meter 6, 10 and 12 mm were drilled without the use of coolants. The idea behind the drilling holes of various diameter was to check whether the smaller diameter holes would be subjected to distortion. The results of test indicate that the drilling of the composite material required lesser torque and thrust force compared to the drilling of the base alloy.