Torque limiting device for air impact tool

An air impact tool has an air motor driving a rotary impact mechanism which has a drive shaft which is coupled to a coaxial load shaft through a torque-limiting clutch mechanism which includes a rigid torque member coupled to one of the shafts and having a peripheral drive surface with drive surface portions, and a yieldable torque member coupled to the other shaft. A plurality of flexible and resilient arms on the yieldable torque member are equiangularly spaced apart around the axis of rotation parallel thereto and are cantilevered from a support yoke, the distal ends of the arms being respectively engaged with the drive surface portions of the torque receiving member. A retaining cylinder encircles the arms and holds them against the drive surface, the retaining cylinder being threadedly engaged with an adjusting member which is rotatable but axially fixed to effect axial movement of the retaining cylinder to vary the retaining force on the torque transmitting arms. Embodiments showing internally and externally threaded retaining cylinders, and planar and concave drive surface portions are disclosed.