I have a confusion between the wrist frame, the tool frame and the end effector as used in the unmodified DH conventions. Can you differentiate with diagrams?
Tool frame is the same as the end-effector. The wrist frame is located at the point where the last 3 axes of the robot, if extended as imaginary lines, intersect (in case of a robots equipped with a wrist). It is oriented the same way as the DH frame of previous axis. A wrist is essentially a subcomponent of the structure (the last 3 axes) used for setting the orientation of the tool.
Sometimes flange frame is also used. That is the physical end of the robot when no tool and tool holder is attached to it. It is usually a ISO flange for mounting tools and tool holders.
UPDATE: coordinate system 4 is the wrist coordinate system and 6 is the tool and end effector frame.