Patent ID: 7640779

Claim:
A holder unit comprising: a base; a working tool holder which is movably supported on said base so that a working tool to be mounted can be disposed at a nonworking position and a working position; and resilient structure to resiliently urge said working tool holder so as to dispose the working tool at the nonworking position, wherein said working tool holder is provided with a through hole having one end open at one end surface of said working tool holder and another end open at another end surface of said working tool holder, and said resilient structure includes a resilient body disposed between the one end and the other end of the through hole, a resiliency receiving body which is detachably fixed to said working tool holder at one end side of the through hole and receives the resiliency of said resilient body, and an abutment body which is movably disposed in said working tool holder at another end side of the through hole, and which is adapted to abut against said base by the resiliency from said resilient body, said abutment body having one of a cylindrical body and a hollow cylindrical body which is movably disposed in said working tool holder at the other end side of the through hole and a rotating body which is rotatably held by said one of said cylindrical body and said hollow cylindrical body and rolls on and abuts against said base.