The relative significance of the major parameters that govern the formability of sheet metal in a stamping operation is generally not well understood because of the complexity of the problem. Much experimental work has been done in this area but has failed to indicate the solution. This work uses a 2-D FEM code to study the sensitivity of several forming parameters that can be easily controlled. To limit the scope of the work, this paper focuses on plane strain deformation mode only because most parts fail under this condition. The results indicate that interfacial friction and the stain hardening ability of the steel are the two most critical factors although geometrical effect also play a role. A good combination of some major factors will provide a consistent process which will tolerate process variability. Detailed discussions are presented in this paper.