HYDRAULIC TORQUE WRENCH

The wrench 10 includes a head 11 having an input 12 for pressurised hydraulic fluid and a rotatable connector, for connecting to an item to be rotated by the wrench. A drive mechanism 13 is driven by fluid from the input and tending to rotate the rotatable connection. A reaction arm 1 mounted 16 on the head selectively allows rotational motion of the arm relative to the head about an axis. The arm is arranged to react against a surface when the drive mechanism rotates the rotatable connection. The mounting 16 includes a splined connection 17 comprising complementary splines 20, 21 on the head and the arm. The connection permits linear motion of the arm relative to the head along the axis from a first position where the splines of the connection interengage so as to prevent relative rotation of the arm and the head, and a second position where the splines do not inter-engage and allow relative rotation of the head and the arm. A travel limiter (7, Figure 9) prevents motion of the reaction arm relative to the head past the second position. At least one biasing member (25, Figure 7) biases the arm into the first position.