A pin assembly (112) suitable for mounting a track roller bogie (5) on a track frame (1) of a crawler type traveling apparatus, wherein first to third rings (114 to 116) are disposed on an outer peripheral surface of a pin (13) having lubricant supply passages. Sealing means (18, 19) are disposed between end faces of the respective rings (114 to 116) and end faces other than those of the sealing means (18, 19) are formed in slide contact faces (114b, 115b; 115c, 116b), which slidably direct contact with each other. As compared with a conventional case in which spacers are installed between the first to third rings, the total wear amount of the slide contact faces is remarkably reduced, the number of parts is reduced by abolishing the conventional spacers which caused defective lubrication, and a load between the rings in a thrust direction is directly received between the rings. As a result, the troublesomeness of an assembly of the track roller bogie and a reduction in service life due to defective lubrication can be eliminated.