This paper presents a study and analysis on the thrust force in the drilling of dissimilar materials. The material used is armor steel-glass fiber reinforced plastic (GFRP) composites. The armor steel is sandwiched between the two GFRP layers. Experimental design technique is used for conducting the experiments. The three panels are drilled, and the influences of feed and spindle speed on the thrust force are measured and mathematical models are established between the drilling parameters. The results indicate that the thrust force required is more for the bottom panel than for the top, most probably due to part of the drill is engaged in the armor plate and the heat is also generated because of higher thrust force experienced in drilling the middle layer. The results are discussed and presented in detail.