Coolant

...back to coolant articles

This article delves into the various types of coolants used in CNC machines, focusing on their unique properties and applications. It explores key categories such as water-soluble coolants, synthetic solutions, and mineral oil-based options, highlighting their benefits and potential drawbacks. By understanding these differences, you can make informed decisions on the best coolants for CNC machines, their tasks and materials.

To date, about 90% of metalworking equipment uses coolant for cooling and lubrication. The remaining 10% can be attributed to dry processing including cooling with compressed air.

Types of Coolant

There are 2 main types of coolant oil used in CNC machines:

1. Insoluble cutting, grinding, forming and other oils
   Pure mineral or ester (vegetable) oils that do not dissolve in water and are used in operations prioritizing lubrication, for example during gear processing, machining on Swiss-type lathes, broaching, or special applications like dielectric fluid for EDM processing.
2. Water-soluble coolants
   On modern CNC machines, in most cases, water-soluble liquids are used, which form an emulsion by mixing with water. The concentrate of such coolants consists of a base (mineral or ester oil, water for synthetic types, or polymers). To obtain a stable emulsion, emulsifiers are added along with anti-corrosion, lubricity, and stability additives. Water-soluble coolants are usually used in diluted form at a concentration of 3–15%.

In turn, water-soluble coolants can be divided into 4 main categories:

A. Coolant based on mineral oils

They contain 50–80% of mineral oils.

Pros:

• High lubricity
• Low cost (least expensive choice)

Cons:

• Low stability and tendency to bacterial contamination
• Low cooling capacity
• Poor flushability (high flow-away rate)
• Poor compatibility with some materials, including aluminum (darkening)
• Dirty work area

CNCmarket.ca does not supply pure mineral oil coolants.

B. Synthetic coolants

They do not contain mineral oils. The base for classic synthetic coolants used in CNC machines is water.

Pros:

• High cooling capacity
• Good washability
• Resistance to bacterial contamination

Cons:

• Low lubricity
• Lower corrosion protection
• Sensitivity to concentration
• Poor compatibility with some materials, including aluminum (darkening or difficulty in small threading and high-speed aluminum operations)

EASYCUT fully synthetic range includes SYN291CO.

C. Semi-synthetic coolants

They contain 5–49% mineral oils.

Pros:

• High cooling capacity
• Good lubricity
• Good corrosion protection
• Resistance to bacterial contamination
• High stability
• Good washability (optimal flow rate)
• Material versatility
• Best value-for-cost ratio

With proper selection and maintenance, semi-synthetic coolants deliver the most balanced performance. The EASYCUT semi-synthetic range includes UNI301 (universal), PRO301 (optimized for aluminum), and BASE201 (basic solution for light-duty machining and grinding).

D. Coolant based on ester (vegetable) oils

They contain 5–49% ester oils.

Pros:

• Environmentally friendly
• High cooling capacity
• Excellent lubricity
• Good corrosion protection
• Resistance to bacterial contamination
• High stability
• Good washability (optimal flow rate)
• Material versatility
• No residue on parts

Cons:

• Higher cost

The best eco-friendly coolant type if it fits your budget. Please check EASYCUT VEG001 for details.

E. High-tech polymer-based synthetic coolants

They contain no mineral oils; the base is polymer (glycol).

Pros:

• High cooling capacity
• Good lubricity
• Good washability
• Resistance to bacterial contamination
• Good corrosion protection
• No residue on parts
• High stability
• Composite and plastic friendly

Cons:

• Higher cost

If you need a heavy-duty synthetic, colorless, and odorless coolant that leaves no residues on your parts, check EASYCUT polymer-based options available through the Coolants section of our catalogue.

Move to other coolant-related articles.