Abstract: A jig is disclosed for assembling a track chain which includes pin adapters and bushing adapters attached detachably to tool bars. Each adapter is provided with an outer cylinder, an inner cylinder received slidably in the outer cylinder, a biasing device held within the outer cylinder for biasing the fore end of said inner cylinder so that it protrudes outwardly from the fore end opening of the outer cylinder, and a stop attached to the outer cylinder for preventing the inner cylinder from protruding excessively out of the outer cylinder. Circular recesses are formed in the inner peripheral surface of the fore end opening of the outer cylinder.

Abstract: A first contact joint screwed to the open end of a lubrication oil passage bore within the shaft of a track roller whose surface is to be rebuilt by welding material thereto, bears cooling medium inlet and outlet ports, bears an intake tube whose length is such that one end is centered axially between radial oil passages constituting branches for the oil passage bore such that a cooling medium fed to the intake terminal of an intake/exhaust sleeve borne by the first contact joint circulates through the track roller in the area of welding for maintaining the track roller surface at relatively low temperature during welding of the built-up material to the periphery of the track roller.