An attrition liner machining tool, configured to machine the surface of an attrition liner provided radially outward of a set of a plurality of fan blades in a gas turbine engine. The tool includes at least one rotating machine tool having a connector at a first end and a cutter at a second end. The connector is configured to rigidly connect to a rotating fan blade mount of the gas turbine engine that, in use of the gas turbine engine, supports the fan blades. The cutter is configured to machine the attrition liner. The at least one rotating machine tool is configured such that, when it is connected to said rotating fan blade mount of a gas turbine engine, the cutter is passed across the surface of the attrition liner when said rotating fan blade mount is rotated.