Attachment pin assembly

An attachment pin assembly for attaching and fixing a drilling tool to an adaptor of an operating machine in a drilling tool attachment state in which the adaptor is inserted into the drilling tool in contact with the drilling tool, the drilling tool being provided with a pair of first through-holes, the adaptor being provided with a second through-hole, and the pair of first through-holes and the second through-hole being arranged to penetrate the drilling tool and the adaptor in the drilling tool attachment state, said attachment pin assembly comprising:

• a first pin body including a first shaft portion inserted into one of the first through-holes and the second through-hole from a first side portion of the drilling tool and a flange portion formed at an end of the first shaft portion;
• a second pin body having a second shaft portion inserted into the other first through-hole and the second through-hole from a second side portion of the drilling tool on an opposite side of the first side portion;
• and
• a bolt inserted into the flange portion and the first shaft portion of the first pin body and the second shaft portion of the second pin body to fasten and fix the first pin body and the second pin body to each other,
• wherein a housing recessed portion for housing a head of the bolt inside the one of the first through-holes is formed at the flange portion of the first pin body, and
• an inside bottom surface of the housing recessed portion is offset towards a tip end side of the first shaft portion with respect to an outside seating surface of the flange portion facing an end of the second through hole.