That's quite a question, i have no idea. I'll have tot test it! Al I can say is the servo should have 10kg/cm torque,
this is how the claw works, the fork (grey) is attached to the servo arm 3cm from the middle, so in worst case it pulls the fork with 3,3kg. around 180 deg. servo rotation the force on the fork can be much much bigger because effectively the length of the arm is decreasing (cos(a)*3cm). When the servo is at 90deg a =0 at 180 deg it is 90. cos(90) = 0 so theoretically is should have infinte force
the distance between the pivot of the claws and where te rods connect is 2cm, if is disregard the rods not being in line with the fork that in worst case leaves me with 1,15kg *2cm = 3,3kg/cm torque on each claw.
the middle spikes of the claw are 4cm from the pivot so at these spikes the pressure should be about 550grams, imagine a pint standing on your hand, on a screwdriver.
the outer edges of the claw are 8cm from the pivot so here it is only 275grams, but the inner spikes are just 2cm out so here it should be 1,15kg. I can tell you it really pinches if you put your finger in there, but pracically nothing ever gets between those points because it's too narrow.