An apparatus for imparting false twist to a staple yarn comprising a yarn guide for guiding a staple yarn along a path and a false twist device comprising a convex surface for engagement with a staple yarn so as to impart a force to the staple yarn when the staple yarn engages with and traverses the convex surface of the false twist device, and wherein the relative positioning between the yarn guide and the convex surface of the false twist device is adjustable such that, when a staple yarn is engaged with the convex surface of the false twist device and extends between the yarn guide and the false twist device, the amount of contact between the staple yarn and the convex surface of the false twist device can be controlled.