Can dirty coolant damage cutting tools?

Dirty coolant has a detrimental effect on cutting tools and can significantly reduce their lifespan. Through wear and tear metal fines contaminate machine coolant and over time this contamination can scratch and chip the cutting tools leading to tool damage. Damaged tools will need to be replaced to avoid poor surface finish quality and product rejects.

How does machine coolant become dirty?

General wear and tear of machinery leads to fine metal particles circulating the coolant. These particles then rub against the machining tools speeding up abrasive wear.

Over time the anti-bacterial properties can break down causing microbial growth. When diluting cutting fluid, it is important to avoid water that is rich in minerals as this will feed fungal growth.

What are the negative effects of dirty coolant?

Dirty coolant loses its lubricity and cooling ability which leads to damaged tools. Metal fines have an abrasive effect on the cutting tool leading to quicker crater and flank wear. Contaminated coolant has a decreased cooling ability which can lead to softened cutting edges, poor machining performance and reduced tool life. Decreased lubrication leads to more friction and premature tool failure. Dirty coolant can also clog nozzles and impact the flow rate.

Contaminated coolant can scratch the workpiece impacting the surface quality. It can also cause rust on the surface of the tool.

Rancid coolant not only smells bad but is also harmful to the health of operators. Cutting fluid with a high microbial growth can lead to respiratory health problems and contact dermatitis. Metal fines in dirty fluid can cause small cuts and abrasions on the operator’s skin which can then become irritated or infected when coming into contact with the coolant. There are around 200 cases of dermatitis reported each year to the European Prevention Initiative for Dermatological Malignancies related to cutting oils and coolant. Breathing in coolant mist is bad for the operator’s respiratory system even when the coolant is clean, so making sure they have limited contact with the cutting fluid is highly recommended. The associated health issues with breathing in coolant mist often become apparent much later in life.

Machine stoppages, frequent barrier filter and tool replacement all cost money, so employing an efficient cleaning schedule and filtration system is critical.

How to prevent dirty coolant

The best way to prevent premature tool damage from dirty coolant is to remove contamination from the cutting fluid. Tramp oil can be removed by skimmers, and ferrous metal fines can be extracted through a magnetic filter. Eclipse Magnetics’ coolant filters are capable of removing metal particles as small as one micron. Magnetic filters won’t strip the coolant of its anti-bacterial properties and therefore extending the life of the coolant and minimising the corrosive effect of dirty coolant on machine parts and workpieces.

It’s best practice to clean the coolant tank and machine sump to prevent build-up of contamination. Inspecting the concentration level and monitoring the PH levels will also contribute to your coolant staying cleaner for longer.

Use deionised water when diluting fresh coolant to prevent fungal growth.

Conclusion

Dirty coolant can have a serious impact on cutting tool performance, surface finish quality, machine efficiency and operator safety. By keeping coolant clean, monitoring concentration and pH levels, and using effective filtration to remove fine metal particles, manufacturers can help extend tool life, reduce downtime and maintain a safer, more efficient machining process.