Abstract: Described is an apparatus 10 and process of filtering metal working fluid containing metal fines comprising: providing a metal working fluid containing metal fines therein 12 wherein the fluid is generated in the working of a metallic member and wherein optionally a substantial portion of the fines is less than about 50 microns in diameter; passing 14 the fluid with fines therein to a cyclone separator 16; recycling 18 a portion of the fluid passing from a first exit 20 of the cyclone separator so that it can be used as a fluid in the metal working process; and collecting 36 a portion of the fines exiting from the cyclone separator.