What I'm trying to do is create a robotic hand. I created the mesh and added the bones for the fingers (following CG Cookies' tutorial on rigging fingers), but didn't add a bone for the "arm" part of the mesh.

I've tried adding the bone (the arm bone is named Bone.020), created a vertex group with the same name, then weight painted the part it should move, but that didn't work. I have tried parenting the finger bones to the arm bone, but that didn't work. I don't know what else to do. Any help is greatly appreciated.

View of the Object Data panel

View of the Bone panel

View of the Bone Constraints panel

Showing the fingers are working properly

The problem - Rotating the arm doesn't pivot where the "elbow" would be

Example of weight paint that works with thumb

The weight paint area for the arm and palm

Armature modifier in the modifiers panel