When I tried to do a Belleville system for my knee mill, I could not find springs with characteristics that would allow me to get the force and travel I needed without a fairly long stack (about 30 springs, about 3", IIRC), even when I went to pretty large diameter (~1.75", IIRC). And, unless you're only running very low speed, even a fairly short stack will need to be contained within some kind of housing, to prevent it from whipping, with ruinous results, when the spindle is on. That housing will then need to be balanced. Perhaps you can find more suitable springs, but I could not. I also found such a short stack of springs, for all practical purposes, could not be compressed beyond their rated force. The friction goes up exponentially beyond that point, making any additional travel come at the expense of extremely high incremental force for a very small incremental travel, even when the springs are well greased. Using a very tall stack allows the response to be nearly linear, as each spring need only move a few thou. VMCs seem to use stacks of about 150 springs, I assume for this very reason.
Regards,
Ray L.