The different types of metal working fluids
1. Straight oils – are also referred to as neat oils. This metal working fluid is petroleum or vegetable-based that is not diluted with water although other additives might be present. Straight oils are used in metalworking processes where lubricity is more important than heat reduction.
2. Soluble oils – are also called as emulsifiable oils that contain 30% to 85% severely refined petroleum oils as well as emulsifiers so as to disperse oil in water. When mixed with water, this metal working fluid forms an emulsion with a milky white appearance. Its high oil content provides excellent lubricity during a cutting operation as well as protection for the cutting tool.
3. Semi-synthetic fluids – contain 5% to 30% severely refined petroleum oils, 30% to 50% water and other additives. This type of metal working fluid combines the physical lubricity of soluble oils with the chemical lubricity, cooling and cleanliness of synthetic coolants.
4. Synthetic fluids – do not contain petroleum oils but uses detergent-like components and other additives to help wet the workpiece. Synthetic oils have excellent cooling properties.
The primary concerns in the use of metal working fluids
When metal working fluid is used, the primary concern is the presence of contaminants that can encourage the growth of bacteria and fungi in the water-based fluids. The presence of bacteria can degrade and change the properties of the metal working fluid. The use of biocides control bacterial growth but this product has hazardous properties. Another source of possible contamination is tramp oil used for lubrication of machines such as hydraulic oil, gear box oil and other lubricants. When tramp oil leaks into the metalworking fluids, it can contribute to bacterial growth being a source of nutrients for bacteria. Metal working fluid can also be contaminated by small particles of metal and alloys in the form of chips and swarfs during machining. Due to contamination, metal working fluids must be handled carefully to prevent ingestion and high exposure for machine operators.
How to work safely with metal working fluids
It is important to obtain the MSDS or Material Safety Data Sheet from the manufacturer/supplier so as to understand the ingredients contained and safety hazards can be minimized. Metal working fluids contain hazardous components and the level of exposure varies with the machining processes as well as such changes that include refining, recycling, degradation or use of reclaimed chemicals and the potential reactions between components. Proper ventilation is encouraged and the operator should not work too close to the metalworking machines. Metal working fluids with the least toxic materials should be used whenever possible.