Hi Hex.... Well I do not know the tonnage or force required, however in my daily delivery dutys I do have access to many industrial shops that make tank heads, one thing they all have in common is that they gradually form the "dish" using huge presses, however they do not press it all at once, well except for the real big one that stamps out two inch thick iron dishes about two feet in diameter in one swelt swoop.. anyway, they start out with a small amount of compression, the hydraulic punch goes up, and they rotate the disc a little with each slow stomp, gradually increasing the " throw" as it starts forming a dish, the bottom is concaved, the top punch is convex, they keep going round and round and gradually increase the throw and shazam... a texas chilie bowl is formed......... they usually have a swatch of carpet on the lower concave die and I have never seen any kind of lubrication used....... I know your application is considerably smaller, however I hope some of this information can be of some use as to your project..... Brian...