In metal cutting operation ninety-seven percent of the energy consumed is converted into heat. If the right kind of cooling doesn’t take place at the cutting edge, the heat can damage both the cutting tool and the work piece as an overheated tool loses its hardness, which shortens the tool life, and an overheated work piece can lose its dimensional integrity. To cool the cutting tool and work piece at the cutting zone continuously; metal working lubricants, coolants and fluids are used. These fluids improve the tool life by reducing wear, increase lubrication, reduce work piece thermal deformation, provide excellent surface finish and flush away chips from the cutting zone. These products are also used to prevent rust and corrosion. In order to realize the lubricating and cooling process watermiscible and nonwatermiscible metalworking fluids have been formulated.
Mineral oil based water soluble fluids forms milky emulsion when mixed with water. The concentrate consists of a base mineral oil and emulsifiers to help produce a stable emulsion. They are widely used in industry and are the least expensive among all cutting fluids.
Synthetic cutting fluids are used in application such as turning, drilling, milling, grinding, tapping, boring, reaming, sawing, slotting and broaching etc. The dilution ratio with water depends on the severity of application.
Neat Cutting Oils are non-emulsifiable and are used in machining operations in an undiluted form. They provide the best lubrication and the poorest cooling characteristics among cutting fluids. They are composed of a base mineral or petroleum oil and extreme pressure additives such as Chlorine, Sulphur and Phosphorus.
Proper selection of a cutting fluid for a given machining operation is vital to get the best results. The basic criteria for selection of a cutting fluid are:
1. Process performance viz. cooling, lubricating, chip flushing, corrosion inhibition, fluid mist generation, fluid carry-off in chips and fluid stability (for emulsions).
2. Cost performance.
3. Environmental performance.
4. Health Hazard performance etc.
Metal working fluids/coolants and must meet the specifications recommended by the OEM/IS or its equivalent standards.