Abstract: An assembly for the attachment of a cutter blade into a chain saw. The saw consists of a frame including controls and drive mechanism as well as a protruding cutter blade (2) encircled by an endless toothed chain that receives its motive power from the shaft of a motor mounted to the frame. The cutter blade (2) and the power transmission unit (16) to be connected to the saw shaft are mounted to an auxiliary frame (18). The auxiliary frame (18) has fasteners (17) and the saw frame is fitted with counterparts (10, 11) for attaching the auxiliary frame (18) into the saw frame (1) using the fastener (17) so that the transmission unit (16) is in power transmitting connection with the saw shaft (4).