This is my first attempt at a gripper design. I will be making changes as I find problems with the design. I am using a standard Hi Tec servo for a template. Also, I will be adding different left and right gripper designs as I need them. The current grippers are designed for adhesive weather strip foam affixed to each side. The small holes can be tapped out with 4-40 or a 3M .5 tap depending. I used 4-40 3/8" and 1/2" cap screws.
Here is a link to alternate grippers for this assembly. http://www.thingiverse.com/thing:621809
Here is the link to the Rob Gripper top plate http://www.thingiverse.com/thing:622861