Abstract: An improved flaring tool includes the usual plurality of expandable die blocks retained by a U-shaped frame. A clamping screw is treaded through a clamp block which is rotatably mounted between the legs of the frame at its open end. The screw is movable toward and away from the die blocks to clamp or unclamp tubing between adjacent die blocks. A conical flaring tip is movable against the end of a clamped tubing for flaring same. The clamp block's axis of rotation is perpendicular to the direction of movement of the die blocks and the screw. The improvement comprises a facility which locks the clamp block against rotation when the screw is aligned with the die block and their direction of movement. The locking facility prevents unintentional rotation of the clamp block as the screw is rotated to clamp or unclamp the tubing, but may be manually overcome to intentionally rotate the clamp block.