The invention relates to a timber working unit for machining crib grooves in the log and for cutting the log to size, the unit comprising at least two device frames (1, 2) disposed at a distance from each other, the distance.between which can be adjusted. The device frame (1) comprises a cutting tool (3) for cutting the log to be worked and a milling tool (4) for machining a crib groove in the log to be worked (5), as well as a conveyor chain (6) with its support arrangements for conveying the log to be worked in the crosswise direction through the manufacturing phases of the device frames. According to the invention, the support arrangements include in the conveyor chain (6) a rigid pusher stop (7) for conveying the log to be worked (5) along with the motion of the conveyor chain; in the machining area of the cutting tool (3) and milling tool (4), a lower support (8) supporting the log; as well as in the machining area of the cutting tool and milling tool, a tightening element (9) provided with elasticity, pressing the log against the lower support. In addition, the machining directions of the cutting tool and milling tool are arranged to press the log to be worked'against a space which is open forwards in the direction of motion of the log and defined by the lower support, pusher stop and tightening element.