Cooling and lubricating with cooling lubricant
During machining, heat is generated by the tool cutting edge engaging with the workpiece. Oil or cooling lubricant is often used to reduce and dissipate the heat generated. Cooling lubricant is also known by the abbreviation "KSS".
Types of cooling lubricant
Cooling lubricants are usually a mixture of oil and water, as water is the best cooling agent and oils are well suited for lubrication.
In addition to water and oil, cooling lubricants also contain an emulsifier so that the oil can be mixed with the water. The emulsion also contains additives that promote certain properties of the metalworking fluid.
Cooling lubricants are divided into two groups:
- Non water-miscible cooling lubricants
- Water-miscible cooling lubricants
Non-water-miscible cooling lubricants
Non-water-miscible cooling lubricants consist of oil (e.g. cutting oil) and are used when the focus is on lubricating the tool. The more viscous the oil, the higher the viscosity of the cutting fluid. Cooling lubricants with a high viscosity are used, among other things, when working at low cutting speeds and with interrupted cutting.
Water-miscible cooling lubricants
Water-miscible cooling lubricants consist of a water and an oil component. The coolant is usually purchased as a concentrate and is then mixed with the appropriate amount of water. This type of coolant has a higher cooling effect due to the water content. Stir the water into the oil when mixing to avoid oil bubbles. Use a measuring cup, for example, to ensure correct dosing. You can use a refractometer to check the correct mixing ratio of the coolant. Also make sure to use water that is as soft and germ-free as possible and at least of drinking water quality, as the water quality has an influence on the cooling lubricant.
Choosing the right coolant lubricant
The selection of the right coolant lubricant depends on the type of machining and the desired effect of the coolant lubricant (cooling or lubricating).
For reaming, for example, pure drilling oil is advantageous, while a water-miscible coolant with an oil content of 5 % or more in the water is suitable for grinding. The oil content should be at least 10 % for the use of cooling lubricants in turning or milling.
Advantages of using cooling lubricant
Use cooling lubricant for greater dimensional accuracy, especially when working on a workpiece for longer periods of time. Advantages of using cooling lubricant:
- The use of a cooling lubricant increases the service life of the tool, as the cutting material is well below the thermal load limit.
- Cooling by the coolant leads to a better surface finish as the friction between the workpiece and the tool is minimised.
- The use of cooling lubricant results in better chip removal, as the chips are "washed away".
- In addition, coolant lubricant prevents corrosion on the machine and the tool.
Working with MWF - Hazards
MWF can be hazardous to health. Therefore, observe the manufacturer's hazard warnings and avoid contact with cooling lubricants or wear gloves and safety goggles if necessary.
Fungi and bacteria can sometimes form in the cooling lubricant. If this is the case, the coolant can no longer be used and must be disposed of in accordance with the regulations.
Tips & tricks
- Do not use commercially available oils (engine oil, household oil, etc.) to produce your own cooling lubricant. These oils settle on the surface as an oil slick, which can lead to the formation of mould.
- Change the cooling lubricant emulsion regularly as it wears out over time and to prevent the formation of mould. Observe the manufacturer's data regarding the recommended change intervals.
- Use a coolant device if you want to process metals for longer and with dimensional accuracy.
- Make sure that the cooling lubricant hits the exact spot where the cutting edge engages in the workpiece (see example in the picture).
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