According to an aspect of the disclosure, a robot arm gripper device includes a grip unit capable of gripping an object by a hinge movement, a power transmission unit coupled to the grip unit and transmitting power to the grip unit, and a buffer unit having one side connected to the power transmission unit and another side connected to a robot arm body, wherein the power transmission unit is movable on the buffer unit.

A device or tool that is configured for gripping a liner in order to to remove the liner, and install the liner in the shell of a mill. The device includes, a rigid structure or frame forming a support for containing the components, a coupling element that allows the device to be secured or disposed on at least one end of a manipulation device, such as a robotic manipulator, and at least one claw or pincer for holding at least one bolt by the head. The tool is designed to allow the adjustment of the relative position thereof in order to align the pincers to the positions of the holes of each liner. The at least one claw is configured to allow the at least one claw to open and close so as to adjust the size of the claw opening to the size of the bolt being gripped. The at least one pincer or claw has at least one sensor, thereby enabling mill liners to be installed and removed.