rohawa:
Well the point was to do a pressure test with the hand. so thats what i was thinking.
I don't know what you mean by 'pressure test'. You want your robotic hand to squeeze some sort of force sensor to measure how much force it is applying? Is this the maximum force it can generate, or do you mean that you want to control the applied pressure as well as the finger positions? It's important to be clear about just what you're trying to achieve.
In any case you will need to decide what maximum force you're designing the hand for, do the mechanical design and calculate the torque required from the servos. This will tell you which servos you need. Or, if you just want to show that a bigger servo produces more force (not sure what the point of that would be) then just buy two sets of servos with different torque ratings. But it seems to me that a working articulated hand is a thoroughly worth while project in its own right and trying to measure or vary the output force would best be handled as a separate project once you have the basic hand working.