Short Answer:

Cutting fluids are liquids used during metal cutting operations to improve tool life and machining performance. Their main function is to cool the cutting zone, reduce friction between tool and workpiece, and flush away metal chips. By reducing heat and wear, cutting fluids help maintain dimensional accuracy and ensure a better surface finish on the machined part.

Cutting fluids can be oils, emulsions, or chemical solutions depending on the machining process. They also prevent corrosion of both tool and workpiece. Overall, the use of cutting fluids increases production efficiency and improves the quality of machining operations.

Detailed Explanation :

Functions of Cutting Fluids

Cutting fluids are an important part of machining operations such as turning, drilling, milling, and grinding. During these operations, a large amount of heat is produced due to friction between the cutting tool and the workpiece. This heat not only damages the cutting edge but can also distort the shape and accuracy of the finished product. Cutting fluids are therefore used to remove heat, reduce wear, and improve machining efficiency. The functions of cutting fluids can be classified into several major categories such as cooling, lubrication, chip removal, cleaning, and corrosion prevention.

Cooling Function:
One of the most important functions of cutting fluids is to absorb and carry away the heat produced during machining. High temperatures can soften the cutting tool material, cause dimensional inaccuracy, and even lead to tool failure. The cooling effect of cutting fluids helps maintain the temperature of both tool and workpiece within safe limits. This is especially important in high-speed operations like drilling and grinding where heat generation is significant. The cooling property depends on the type of fluid used — water-based fluids have better cooling capacity compared to straight oils.
Lubrication Function:
Lubrication is another vital function of cutting fluids. When a metal is being cut, the friction between the chip and tool face is very high. A thin film of lubricant between the tool and chip reduces this friction, making cutting smoother and requiring less power. It also prevents the welding of the chip material to the cutting edge. This reduces tool wear and improves surface finish. Mineral oils and emulsions are generally used for lubrication because of their ability to form a protective layer on the cutting surface.
Chip Removal or Flushing Action:
During cutting, small pieces of metal called chips are produced continuously. These chips can stick to the cutting zone and cause scratches on the machined surface or damage the tool edge. Cutting fluids help by washing away these chips from the cutting area. This flushing action keeps the cutting zone clean and prevents re-cutting of chips. It also allows better visibility of the work area for the operator, improving the accuracy of the machining process.
Cleaning Action:
Cutting fluids also keep the workpiece and cutting tool clean. They remove tiny metal particles, dirt, and other contaminants that may affect the quality of the machined surface. A clean cutting environment reduces the chances of surface defects and ensures smoother operation. Some cutting fluids contain additives that enhance their cleaning property.
Corrosion Prevention:
After machining, both the workpiece and the machine components are exposed to moisture and chemicals which may cause rust or corrosion. Cutting fluids form a thin protective layer that prevents oxidation and rust formation. This function is particularly important in machining ferrous materials like steel and cast iron. Additives such as corrosion inhibitors are commonly mixed into cutting fluids for this purpose.
Improvement in Tool Life and Surface Finish:
Because cutting fluids reduce temperature, friction, and wear, they significantly increase the life of the cutting tool. The tool remains sharper for a longer time, reducing replacement cost and machine downtime. Additionally, reduced friction leads to a smoother cutting process, which improves the surface finish of the final product.
Reduction in Power Consumption:
Friction during metal cutting requires additional power to overcome resistance. Cutting fluids minimize this resistance, leading to a reduction in cutting forces and overall power consumption. This results in cost savings and makes machining operations more efficient.
Safety and Operator Comfort:
Modern cutting fluids are designed to be safe for operators. They reduce dust, fumes, and chip adhesion, making the work environment cleaner. They also reduce vibration and noise in high-speed operations, leading to safer and more comfortable working conditions.

Selection of Cutting Fluid Based on Function:

The selection of cutting fluid depends on the type of machining process, material of the workpiece, cutting speed, and desired surface finish. For example, high-speed operations require fluids with good cooling properties like water-based emulsions, while heavy cutting of hard materials may need lubricating oils. Using the right fluid ensures that all functions—cooling, lubrication, and cleaning—are effectively performed.

Conclusion:

In machining operations, cutting fluids perform several important functions that directly affect the quality, accuracy, and economy of production. Their primary roles are to cool the cutting zone, lubricate tool and workpiece surfaces, remove chips, and prevent corrosion. The use of appropriate cutting fluids not only enhances tool life and surface finish but also ensures smooth and efficient machining operations. Therefore, cutting fluids are an essential part of any modern metal cutting process.