The spindle usually uses cooling oil circulation system, cooling oil through the oil temperature control system after flowing through the spindle to cool the whole spindle; At the same time, the cooling oil is affected by centrifugal force when the spindle rotates at high speed and enters the small hole on the inner ring of the spindle bearing to directly lubricate the interior of the bearing. This cooling and lubrication method, called spindle center cooling and internal pressure lubrication, ensures that the spindle can continue to work at high speeds for a long time. However, the quality of spindle cooling oil will directly affect the effect of cooling lubrication and the service life of spindle, so the selection of high quality spindle coolant is particularly important.

Spindle coolant is a coolant containing special additives that can be used in liquid-cooled engine cooling systems operating at low temperatures (below 0℃). Automobile engine coolant has four functions: cooling function, anti-freezing function, anti-boiling function, anti-corrosion function. According to the composition of additives: no model, with model; According to the base liquid: inorganic salt type, methanol type, ethanol type, glycerin type, ethylene glycol type, diethylene glycol - ethylene glycol type, propylene glycol type, dimethyl inkstone type; According to engine load (strengthening factor) : light load engine coolant and heavy load engine coolant; According to whether regeneration: non-regenerative type and regenerative type; Other categories: hard water resistant, corrosion resistant cooling water, emulsified oil coolant, etc.

The ideal state of the spindle coolant is free of any solid impurities, but in practical use, the coolant will inevitably be mixed with chips from cutting, especially in the processing of cast iron and plastic parts with chips as powder. Impurity in liquid coolant will through the role of the cooling hole cutting tool in cutting area, so the impurities will be repeated cutting, the greater the volume of impurities, the circulation of coolant in cutting impurities will be repeated, the more the tool wear and workpiece processing effect will be obvious, this is connected and mesh filter function.

If the filter can filter out impurities with a diameter of more than 5 microns, then the coolant acting on the cutting area will contain no more than 5 microns of impurities; If the screen has a larger aperture, say 106 microns, then impurities less than 106 microns in diameter will be incorporated into the coolant throughout the cycle. Therefore, the quality of coolant used in the cutting area largely depends on the filter screen. The smaller the filter hole of the filter screen, the smaller the volume of impurities in the coolant will be, and the number of impurities will be less.