Abstract: A hole saw assembly including an elongated arbor, a mounting piece arranged around the arbor and rotationally locked to the arbor but slidable over the arbor, a circular saw blade mounted on the mounting piece, the rotational axis of the circular saw blade coinciding with the longitudinal axis of the arbor, a central drill extending along the rotational axis of the circular saw blade and being rotationally and axially fixed to the arbor, means for releasably fixating the mounting piece in relation to the arbor at one or more positions along the arbor and a plug ejector for ejecting a plug of sawn material from the interior of the circular saw blade by sliding the mounting piece and the circular saw blade in relation to the central drill and for working as a stop for the sliding of the mounting piece towards the tool end of the arbor.

Abstract: A power tool adaptor for holding a tool adapted thereto including an adaptor body, a tool insertion cavity formed in an end of the adaptor body for receiving the tool, an elongated tool bit insertion cavity formed as a continuation of the tool insertion cavity, means for fixating the tool by protruding into one or more fixation recesses on the outer surface of the tool and means for attaching the power tool adaptor to a power tool; a reversible tool bit holder is further disclosed for holding two changeable tool bits, which reversible tool bit holder is adapted to fit into the power tool adaptor, along with a kit including a power tool adaptor and a reversible tool bit holder adapted to fit into the power tool adaptor.