Short Answer:

Cutting fluids are special liquids used in machining operations to cool and lubricate the cutting tool and workpiece. They help reduce friction, remove heat, and improve surface finish during metal cutting. The use of cutting fluids also increases tool life and ensures smooth chip removal.

There are different types of cutting fluids based on their composition and function. The main types include water-based fluids, oil-based fluids, emulsions, chemical fluids, and gaseous fluids. Each type is selected depending on the machining process, workpiece material, and desired cooling and lubrication requirements.

Detailed Explanation :

Types of Cutting Fluids

Cutting fluids are essential in machining operations to reduce heat and friction between the tool and the workpiece. They improve tool life, machining accuracy, and surface finish. These fluids act as coolants, lubricants, and chip removers during the cutting process. The proper selection of cutting fluid depends on the type of material being machined, the speed of operation, and the required surface quality.

The major types of cutting fluids are classified into the following categories:

1. Water-Based Cutting Fluids

Water-based cutting fluids are mainly used for cooling purposes because water has a high heat absorption capacity. However, since water alone does not have good lubrication properties, additives like rust inhibitors are added.

• Pure Water: It provides excellent cooling but poor lubrication. Hence, it is rarely used alone.
• Soluble Oils (Emulsions): These are mixtures of mineral oil and water with emulsifying agents. When mixed with water, they form a milky fluid that provides both cooling and lubrication. They are widely used in general machining operations.
  Advantages:
• Excellent cooling ability.
• Reduces tool temperature effectively.
• Low cost and easy to prepare.
  Disadvantages:
• Causes corrosion if not treated properly.
• Requires regular maintenance to avoid bacterial growth.

2. Straight or Oil-Based Cutting Fluids

These fluids consist mainly of mineral or vegetable oils and are used where lubrication is more important than cooling. They are best suited for low-speed machining and heavy-duty cutting operations.
Types:

• Mineral Oils: Derived from petroleum, they provide good lubrication and are used in operations like tapping or threading.
• Fatty Oils (Vegetable or Animal Oils): These have better lubricating ability and are often blended with mineral oils.
  Advantages:
• Excellent lubrication and reduced friction.
• Protects the workpiece surface and cutting tool from wear.
  Disadvantages:
• Poor cooling capacity compared to water-based fluids.
• May produce smoke or mist at high temperatures.

3. Emulsion or Soluble Oil Cutting Fluids

Emulsion fluids are a mixture of oil and water, generally containing 5% to 10% oil. They combine the cooling property of water and the lubrication property of oil. Emulsifying agents are added to maintain a stable mixture.
Advantages:

• Provides both cooling and lubrication.
• Suitable for a wide range of machining operations.
• Easy to handle and economical.
  Disadvantages:
• Can promote bacterial growth.
• May cause rust if the concentration is not maintained.

4. Chemical or Synthetic Cutting Fluids

These fluids are made from chemical solutions without any oil content. They contain corrosion inhibitors and other additives to improve performance.
Types:

• True Solutions: Contain chemicals fully dissolved in water, offering excellent cooling and rust protection.
• Semi-Synthetic Fluids: Contain small amounts of oil along with chemicals, providing both cooling and lubrication.
  Advantages:
• Excellent cooling and corrosion resistance.
• Long fluid life and easy to clean.
  Disadvantages:
• Poor lubrication compared to oil-based fluids.
• May cause skin irritation if not handled properly.

5. Gaseous Cutting Fluids

Gaseous fluids include air, nitrogen, or carbon dioxide used as cooling media in high-speed or dry machining. They are supplied through compressed jets to cool the cutting zone and remove chips.
Advantages:

• Clean, non-toxic, and environmentally friendly.
• No fluid disposal problem.
  Disadvantages:
• Provides very little lubrication.
• Limited use for heavy-duty operations.

Functions of Cutting Fluids (Brief Overview)

Although the question focuses on types, it is useful to understand why these fluids are applied in machining:

• Cooling: To reduce the heat produced by friction between the tool and workpiece.
• Lubrication: To minimize wear and friction at the cutting interface.
• Chip Removal: To carry away chips and prevent tool damage.
• Corrosion Prevention: To protect both tool and workpiece from rust.

Selection of Suitable Cutting Fluid

The selection depends on:

• Material of Workpiece: Hard materials need high lubrication, while soft materials need better cooling.
• Operation Type: Heavy cutting like turning or threading needs oil-based fluids; high-speed cutting like grinding needs water-based fluids.
• Machine Speed: High-speed machining prefers emulsions or synthetics for cooling.

Conclusion:

Cutting fluids are essential in machining operations for improving tool life, reducing friction, and enhancing surface finish. They can be classified into five main types: water-based, oil-based, emulsion, chemical, and gaseous fluids. Each type has its advantages and is selected according to the machining conditions and material type. The proper choice and maintenance of cutting fluids ensure efficient machining, longer tool life, and better product quality.