VIDEO: What Coolant Should You Use When Solid Milling?

Optimization can be done with three vital things that determine the impact of the use of coolant. Choose the correct type of coolant media, apply the coolant correctly, make sure it's positioned respecting workpiece, tool part, and tool if done properly. For example, the video on the left shows a good machining setup where for the video on the right the tool holder is way too thick compared to the used end mill, resulting in that the coolant liquid will not reach the cutting edge. And third, maintain the coolant in its best possible condition, for instance by using a good filter.

The most used coolant medias in milling are emulsion coolant, which is a mix of water and oil, which is the most used coolant media. Second, pure oil which is used in some machines instead of the emulsion coolant. Third is compressed air which is used for chip evacuation, but does not take away the heat in a good way and fourth is MQL or mist spray. This is compressed air with a minimum quantity of oil for lubrication.

So let's first zoom in to these four types of coolant medias. First one is emulsion coolant. Emulsion coolant is the most applied in many segments, materials, and milling machines. Emulsion coolant is a mix of water and oil. This mix is the percentage of oil in the mixture. Often this is adapted based on the typical materials which are being machined. Because the thermal conductivity of water is three times higher than that of oil, its cooling performance is very good. Water cools when it's in liquid and even better when it's vaporized. This is called evaporative cooling. The additional oil does multiple things. It lubricates and also resists rust.

Then the second one, pure oil. Pure mineral oil is also used. This can be applied in multiple setups while using many types of oil, with nozzles all fully submerged. This is typically used when a superb surface finish is required.

And third, compressed air. Of course also compressed air should be considered. The air ensures chip removal from the chemical cutting zone and will have some coolant effect that not too much though. The compressed air typically is used in combination with relatively easy to machine materials and composite or graphites. The parts remain clean and dry when using compressed air.

Compressed air is also used when machining with ceramic end mills, for instance our GCG790. During this process it's desired to keep the heat in the chip as much as possible.

And fourth, MQL or mist spray. The mist spray is a mix of compressed air with tiny droplets of a specific oil. In this case, compressed air is used to remove chips while the oil droplets will get some lubrication and this is mainly used in situations where using emulsion coolant can lead to thermal shock effects. That's it for today. Thanks for listening and have a good day. Bye.