Cutting fluids for CNC machining processes

A cutting fluid is a substance designed specifically for metal-working and machining processes where it acts as a coolant and lubricant. This fluid is applied while the machining is being done. Application methods for cutting fluids include flooding, fluid jetting, mist spraying, etc.

Types of Cutting Fluids

Cutting fluid is essential for its cooling, lubricating, debris-cleaning, and corrosion-prevention properties.

The cutting fluid required will vary depending on the kind of manufacturing operation you are carrying out, so you should select your cutting fluid appropriately.

• Soluble oils (Emulsions)

Trim Microemulsion cutting fluid

Soluble oils are made by adding mineral oil to water in particular proportions (1 to 20% oil to water). It contains various additives like sodium sulfonate to enhance the mixing of oil and water, biocides to inhibit bacterial growth, anti-wear additives to enhance lubrication, and anti-corrosion additives to improve corrosion-resistant qualities.

Soluble oils are the least expensive and most common type of cutting fluids used in machining operations. Compares with synthetic cutting fluids, Emulsions provide better lubrication and anti-corrosion.

• Straight oils

CNC Cutting oil

Straight oils are derived from animals or plants. They provide excellent lubrication, and the lack of water content improves their rust prevention properties. Although their biodegradability makes them environmentally-friendly, they’re decompose fast and more expensive than other cutting fluids.

For this reason, pure oils are only added to other cutting fluids as supplements to enhance lubrication during heavy-duty drilling and cutting operations.

• Synthetic Fluids

Synthetic CNC cutting fluid

Synthetic fluids are formed by the solution of organic and inorganic chemical compounds in water, together with additives. Among the additives are corrosion and rust inhibitors as well as lubricant additives.

Chips from the work area can be effectively cooled and cleaned with synthetic fluids.

• Semi-synthetic fluids

Semi-synthetic fluids are made from synthetic fluids, water-based fluids, and soluble oils emulsions. These are composed of a blend of 5–50% mineral oil, chemical compounds, and additives that dissolve in water to create microemulsions with particles ranging in size from 0.1-0.01 mm. The characteristics of synthetic fluids and soluble oil are combined in semi-synthetic fluids. Semi-synthetic fluids are usually used as cutting fluids.

Just How to Choose Right Cutting Fluid?

The selection of a cutting fluid depends on a number of factors including cutting tool type, workpiece material, and machining operation.

Cutting tool type

A carbide tool can heat up quickly. Because of this, they are more vulnerable to thermal shocking, a phenomenon in which the cutting tool's various parts expand to differing degrees. For this kind of tool, synthetic cutting fluid with extremely high cooling capabilities is advised.

Although they don't get as hot as carbide tools, high-speed steels can get hot. Semi-synthetic fluids and soluble oils work well.

Workpiece substance

The most common type of workpiece material that needs cutting fluids is metal. The most commonly machined metals and the appropriate cutting fluids for them are listed below.

•      Steel – Mineral oils containing lubricant additives

•      Alloy steels – Sulphur brass oil or mineral oil

•      Aluminum – Soluble oils or mineral oils without active Sulphur (active Sulphur stains aluminum)

•      Copper – Soluble Oils

•      Stainless steels – Mineral oils containing excellent Extreme pressure additives

•      Cast iron – None

Machining operation

Drilling, turning, milling, and other relatively simple machining operations are performed at relatively high speeds. A significant amount of cooling is necessary at such speeds. Extreme pressure properties and minimal lubrication are needed. Therefore, the best fluids for these kinds of operations are synthetic fluids.

However, effective lubrication is necessary for difficult machining processes like thread cutting and broaching. Cutting fluids with exceptional lubrication and extreme pressure properties are necessary for these operations because they occur at low speeds and high pressures. The best option is to use mineral oils with extreme pressure additives.