The oil used for turning as a lubricant for tools
consists of approximately 95% water and 5% oil and turning chips.
Typically, the oil is water-soluble, creating a solution called a
lubricating coolant, which a mechanical separator cannot separate
without the aid of chemicals (and/or high temperature).
Conversely, oil used for gear cutting in
mechanical workshops for producing mechanical parts is contaminated
only with turning chips. This oil is particularly important because
it can be reused in the process.
To clean the oil from its solid components, such
as chips, centrifuges are recommended, specifically basket-type or
similar centrifuges.
A special case occurs when water-insoluble oil
mixes with the lubricating coolant. For this situation, a vertical
three-phase centrifuge can be used to separate the lubricating
coolant from the oil and the solids. Small-sized centrifuges for this
application are also available on the market.
Another specific case is oil contaminated with
non-metallic solid residues that degrade over time, forming gums or
other defects in the oil. In this scenario, it is possible to clarify
the oil, making it reusable even if not brand new.