Experimental Investigation on Tapping of Al6061/SiC Metal Matrix Composite with straight fluted HSS Machine Taps

The present study deals with tapping of Al6061/SiC metal matrix composite. Stir casting technique was used for the fabrication of composite. Castings were produced by varying weight percentage of SiC (5%, 7.5% and 10%) of 23μm size in Al6061. The fabricated specimens were characterized for their hardness and tensile strength. It was found that hardness increases by the addition of SiC. Due to the presence of SiC reinforcement that is highly abrasive in nature makes machining difficult and produces high rate of tool wear. The tapping experiments were conducted for the machinability study of Al6061/SiC metal matrix composite by using M8 x 1.25 HSS machine taps. Tapping operation was performed under dry condition with different cutting speed (12m/min, 14m/min and 16m/min) and constant feed rate equal to the pitch of thread. Torque required for tapping was measured using piezoelectric based 4 component Drill tool dynamometer 9272A (Kistler make). Surface morphology amd profile of thread surfaces were analyzed using Scanning Electron Microscope (SEM) and metallurgical microscope. Estimation of progressive flank wear of machine taps was undertaken using profile projector. The performance of HSS machine taps was evaluated in terms of tapping torque, tool flank wear and surface characteristics of thread surfaces. The flank wear of uncoated HSS machine taps increased with increase in weight percentage of SiC in Al/SiC composite for a particular cutting speed. Further, when the matrix materials were reinforced by the same kind and same weight percentage of SiC particles, the flank wear of the tool was found to increase with cutting speed. In addition to this, the damage caused to thread profiles increased with increase in cutting speed and weight percentage of SiC