An apparatus for on card cleaning and grinding of revolving flats (4) in a carding machine is disclosed. The apparatus mounts an interchangeable rotary cleaning brush (14) or grinding wheel (16) on a wheel drive (11) so that the wheel can be spun around an axis lateral to the path of the revolving flats (4). During a carding operation the height of the cleaning brush (14) is accurately adjusted by a precision feeding mechanism so that the brush cleans down to the surface of the revolving flats of the revolving flats (4) and so cleans and polishes the wires (4b) and the fouling which commonly accumulates beneath the points (4c) of the wires. The brush (14) can readily be replaced by a grinding wheel with a peripheral grinding surface. The height of the grinding wheel can be accurately set by the use of the precision feeding mechanism so that the wires are reground while still on the card by driving the revolving flats (4) around the path and simultaneously spinning the grinding wheel and traversing the wheel laterally across the bare flats. The combined motions of the wheel and the flats result in a regrinding of the points which closely resembles the optimum regrinding pattern.