A fixture for locating a straight edge of a curved surface of a part and holding the part in a fixed position during performance of a machining operation on the straight edge is described. The fixture includes: one or more supports for seating a convex curved surface of the part, one or more detachable end stops arranged to extend in a plane orthogonal to that in which the supports sit and against which, in use, the straight edge can be aligned, and a clamp arranged, in use, to push the convex curved surface against the supports such that the straight edge contacts the supports without obstruction of the straight edge.