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Maintenance Tips For Metalworking Fluids

Monitoring and maintaining metalworking fluids will help to prolong their effectiveness and protect users against potential health and safety hazards. Using the right equipment is essential to get the most out of your metalworking fluids so here is a list of the main items you’ll need;

Tramp Oil Removal

Tramp oil (also known as sump oil) is unwanted oil that has seeped into metalworking fluid. It often appears as a film or skin on the surface of the coolant or as visible, floating specks of oil. It is important to remove this unwanted oil as soon as possible to protect the integrity of the metalworking fluid and ensure its effectiveness. The best way to do this is by using a mechanical skimmer or vacuum system to remove any surface oil.


A dipslide measures the growth of bacteria, fungi and yeast accumulating within a metalworking fluid. Excessive contamination will degrade the fluid and could become a health and safety hazard to workers if left untreated.

PH Indicator Strips

The majority of metalworking fluids are designed to be alkaline, but when contaminated with bacteria their PH will change to become more acidic. Again, this poses a health risk to workers if left undetected.

Concentration Control

Maintaining the correct concentration for a fluid is important to ensure it works as it should. To determine the concentration, a refractometer can be used to measure the amount of light that travels through the liquid using a % Brix scale.

A mixer unit will also help you to get the right dilution of metalworking fluids whilst allowing you to constantly monitor and change as necessary. This will conserve cutting fluid by only using the amount needed (this will be defined in the supplier recommendations)

Swarf Spinner

Swarf spinners enable metalworking fluids to be continuously recycled by separating waste metal from the coolant. This means the fluid is left uncontaminated and is safe to use again.

Developing a Maintenance Program

Regularly checking and treating metalworking fluids is the key to extending the life of the liquid and complying with health and safety regulations designed to protect users.

There are a number of weekly and daily checks that should be performed to monitor the fluid. Such as;

  • Visually checking the fluid to make sure it hasn’t changed in colour or odour. If It looks and smells different it could be contaminated. This check should be done on a daily basis prior to use.
  • At least once a week use pH indicator strip to measure the acidity of the fluid to confirm that it remains within the manufacturers specified range.
  • Measure and track any microbiological contamination within metalworking fluids using a dipslide. This should be done at least once a week or bi-weekly if your record shows that the fluid is under control.
  • Check and remove any tramp oil that has leaked into the cutting fluid. This can be done via a measuring cylinder or a simple visual check and to remove a tramp oil skimmer or vacuum system can be employed.