30 ceramic materials like silicon nitride have very low ductility and compressive forces are ideally tolerated by the material while tensile forces are not as well tolerated by providing the uniform compressive force caused by the contoured sides on the die inserts which focus the compressive forces on the upper and lower die inserts 25 30 any tensile forces which might damage the die inserts 15 20 on the die inserts are minimized and die life is therefore maximized referring now to fig2 several alternative embodiments of the die inserts 2 a 2 b and 2 c a side view of lower die 20 and lower die insert 30 and a bottom view of the top die insert 25 are shown in fig2 a the upper die insert 25 has a rectangular top portion 50 a rectangular bottom portion 55 and four angled side surfaces 60 that attach the top portion 50 to the bottom portion 55 similarly the lower die insert 30 mirrors the upper die insert 25 in fig2 b upper die insert has a circular top portion 65 a circular bottom portion 70 and a conical side surface 75 joining the top portion 65 to the bottom portion 70 so that the die looks like a truncated cone similarly the lower die insert 30 mirrors the upper die insert 25 in fig2 c upper die insert has a bowl shaped top and side portion 80 and a circular face portion 85 so that the die looks like a bowl similarly the lower die insert 30 mirrors the upper die insert 25 ideally the side surface forms an angle a that is greater than 90 u00b0 between the side surface 60.