Metal removal processes, such as machining and grinding, performed with CNC machines and cutting tools, normally require the use of Cutting Fluids to aid operations. Either a straight un-diluted cutting oil or a water-soluble ‘coolant’ is used, to perform the following functions:
1.) LUBRICATE – a cutting fluid reduces the frictional dynamics encountered when a cutting tool made of very hard materials is used to cut a metal workpiece. In doing so, tool life may be maximized, allowing for a tool’s ‘good’ economic working life. In addition, providing lubrication reduces the energy required to cut through metal, and imparts a good surface finish on the parts machined.
2.) COOL – as temperatures at the tool-work-piece interface can reach 700oC at contact, a cutting fluid absorbs heat in order to prevent the occurrence of built-up edges, a phenomenon wherein metals removed from the work-piece, or chips, are welded into the cutting tool. A tool with a built-up edge will, of course, be dimensionally incorrect, and thus producing defective work-pieces. cooling is also needed the lessen the impact of thermal fatigue on the tool.
3.) PREVENT RUST AND CORROSION – since ferrous metals, such as steels, are prone to rust-formation when exposed to oxygen and moisture, an effective cutting fluid should provide short-term rust protection. In the case of non-ferrous metals like aluminum, copper, and zinc, a cutting fluid should contain additives that prevent staining or corrosion.
4.) WASH AWAY CHIPS – lastly, the cutting fluid should act like a flushing fluid, removing or washing away the metal chips away from the machining and grinding area, as the recirculation of the debris may negatively affect both tool life and surface finish.
Succeeding chapters will tackle the various cutting fluid technologies currently available in the market.
