English (Honk KOng)Hong Kong S.A.R of China

The different types of metal working fluids and their importance

Metal working fluids, or MWFs, are a range of oils or other liquids that can be used to cool, lubricate and reduce friction during grounding, machining and cutting processes (amongst many others).

Different types of metal working fluids

While there can be many additives to metal working fluids, there are four common classes:


  • Straight oils (neat or cutting oils) - a versatile MWF that can be made up of petroleum, vegetable, animal or marine oils. Straight oils are not diluted and tend to be used for heavy-duty machining processes. Extreme pressure agents are regularly added to straight oils to enhance performance.

  • Soluble oils (emulsifiable oil) - made to cool and lubricate, particularly in cutting and grinding. Soluble oils prevent welding between the cutting tools and workpiece. They also prevent the wearing of the tool. Soluble oils contain pure petroleum oils (40-70%) and emulsifiers which help the oil spread and make it milky in appearance.

  • Semi-synthetic fluids - contain 5-30% pure petroleum and diluted with 30-50% water. Semi-synthetic fluids can contain many additives such as; chlorine, sulfur and fatty acids. The fluids work to cool and lubricate and are used in all forms of metal cutting.

  • Synthetic fluids - there is no petroleum oil in a synthetic MWF. They are diluted with simple synthetics, organic and inorganic salts to form a clear solution. They are used to continually dampen the workpiece to prevent mist and smoke, particularly during the grinding process. Synthetic fluids can be harsh on the tool over time causing corrosion.

Working with MWFs

While MWFs can help improve the health and safety of the workplace significantly, exposure to them can carry serious health risks. It is widely recognized that skin contact or inhalation from the fumes of MWFs can cause dermatitis, cancer, lung disease, and asthma.

The United Kingdom Lubricants Association has put together a ‘Good Practice Guide for Safe Handling and Disposal or Metalworking Fluids’. This is essential reading for any company that is considering working with MWFs. The guide is a breakdown of good practice required when working with and maintaining them, as well as exposure control guidelines.

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NCH Lubricants provides cost-effective metal working fluids that can reduce biological growth, ultimately leading to increased sump life. Our solutions provide a balance of both lubrication and corrosion protection to improve and increase tool life. 

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