Abstract: A device at impact wrench, particularly for wheel nuts and wheel bolts and of the type which incorporates a shaft (2) with a handle (3) in one end and a socket in the opposite end (4), whereby the shaft between its ends is provided with a hub (6) about which is rotatably arranged an impact arm (8) which carries weights and is arranged to transfer impact movement to the shaft via stops (7) arranged at the hub, whereby in connection to the hub (6) is arranged members (7, 10) arranged to limit the ability of the impact arm (8) to transfer movement to the shaft (2) which carries the socket in one direction of movement of said impact arm.