There is provided a tool for repair of damaged threads of screws, including a body (2) having a projecting portion (4) for accommodating a screw to be repaired and having two recessed major surfaces;a cutting blade (6), having a rear end hingedly articulated to the body (2), and a front end in the shape of a cutting face (46) substantially fitting the type of thread to be repaired; a guide blade(7) having a rear end hingedly articulated to the body (2), and a front end substantially fitting the type of thread to be repaired, the guide blade projecting beyond the cutting face of the cutting blade, and; means (10, 12, 14) to alter the distance between the front ends and the projecting body portion (4) to accommodate screws of different diameters.