A variable geometry turbine

A variable geometry turbine 1 of the kind used in a turbocharger comprises a turbine wheel 4 supported in a housing 5 having a gas flow inlet passageway 13 defined between an annular wall of a movable wall member, such as a nozzle ring 14, and a facing wall such as a shroud plate 15. The nozzle ring 14 is moveable axially relative to the housing 5 to vary a width of the inlet passageway 13. An annular array of vanes 17 extends across the inlet passageway 13, the vanes 17 having an axial height extending from a root 26 to a tip 27. Each of the vanes 17 is receivable in a corresponding slot 18 provided in one of the walls. Some, most or all of the vanes 17 are tapered along their axial extent, eg by increasing the machining tolerance towards the vane tip, such that they are thinner at the tip 27 than the root 26 to avoid sticking of the vanes when the nozzle ring 14 is moved to more open positions. The amount of taper may vary eg non-linearly.