Engineering Reference

Minimum quantity lubrication (MQL)

Delivering a small, precisely metered quantity of lubricant in an air stream instead of flooding with coolant.

Definition

MQL uses millilitres per hour where flood cooling uses litres per minute. The benefit is not just cost: no flood coolant means no coolant disposal, no mist, and no thermal shock from sudden cooling, which is what causes thermal cracking in carbide.

Its limits are real. It does not remove heat, so it suits operations where most heat leaves with the chip — aluminium, cast iron, and high-speed machining — and struggles in deep-hole or low-speed work where heat builds up.

Common misuse

Assuming MQL will replace flood coolant everywhere. It is a lubrication strategy, not a cooling one.

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