Table of Contents
What is Cutting Fluid?
Cutting fluid is a type of coolant having lubricating properties as well which is used in almost all the metalworking processes during different machining operations such as turning, drilling and milling.
The metalworking process requires several components such as Machine Tools, Raw Materials, and Appropriate Cutting Tools. Cooling lubricants play an important role in smooth cutting operations.
When the machining is done at low cutting speed then cutting fluid required for lubrication purpose whereas when machining is done at high cutting speed then cutting fluid works as a coolant.
In machining processes, different kind of cutting fluids are used as per the requirements. Coolant selection depends on many factors such as cutting speed, material, machining process, finish and cutting tool. Most cutting fluids are some kind of emulsion.
Oil-in-water emulsions and the rest are simple oils, gels, air and gases. Cutting oils are made from animal fats, vegetable oils, and vegetable oils, most of which are made by the petroleum distillation process.
Function of Cutting Fluid
The main functions of cutting fluids are cooling and lubrication. In the machining process, heat is generated by friction between the cutting edge of the tool and the workpiece. So lubrication reduces friction and automatically controls heat generation. A pressurized supply of cutting fluid allows chips to be blown off the machine bed.
Types of Cutting Fluids
1. Liquid Type Cutting Fluid:
Liquid coolant means an aqueous emulsion of oil. Although water alone is an excellent heat conductor, it cannot be used as a cutting fluid due to its corrosive and non-lubricating effects. Mineral oil, known as a semi-synthetic coolant, is added to the water to create a suitable cutting fluid. Other fluid cutting fluids include kerosene, motor oil, etc. used for specialized machining.
2. Semi-Solid Cutting Fluid:
Semi-Solid Cutting Fluids are gels and pastes used for special applications where liquid cutting fluids do not work such as Drilling, drilling, tapping. More expensive than liquid cutting fluids, but consumes less and does not require continuous supply.
3. Gaseous Cutting Fluid:
When talking about gaseous cooling lubricants, compressed air is the best and least expensive cooling lubricant because atmospheric air is used as the cooling lubricant. A liquid may be used with compressed air to provide a mist to the cutting edge. Compressed air blows chips away and air acts as an excellent coolant due to its high thermal conductivity.
4. Aerosol Cutting Fluid:
Aerosol means mist. Air with small droplets of liquid cutting oil. For use where liquid cooling lubricant alone does not work. Liquids are properly atomized using compressed air. Working with aerosols is hazardous to operator health, so good ventilation and good equipment are required when using this type of cutting fluid.
Properties of Cutting Fluid
Cutting fluids used in machining processes require certain properties. These properties vary from metal to metal. A cutting fluid is a good one if it meets all of the following characteristics:
1. Viscosity:
A suitable viscous liquid is required as cutting fluid. Different machining processes require different fluid viscosities. Therefore, a suitable viscous liquid must be supplied to the cutting position. In most cases, a low-viscosity cooling lubricant is required as a continuous supply of cooling lubricant is required during machining.
2. Non-corrosive:
A good cutting fluid should be non-corrosive to work materials and machine parts. The main purpose of adding mineral oil to water is to reduce the corrosive effects of cutting fluids. Water emulsion based cutting fluids have excellent non-corrosive properties.
3. Non-Toxic:
The cutting fluid is non-toxic and must be environmentally friendly for workers as large amounts of cutting fluid are used during the machining process.
4. Good Lubricant:
This is another important property of cutting fluids. This is because the cutting fluid provides lubrication between the cutting tool’s cutting edge and the chips formed by this heat generation, reducing friction between the cutting tool and the work surface.
5. Non-Reactive:
Cutting fluids must be inherently non-reactive, as reactivity can damage machine parts.
6. Heat Transfer Properties:
A good metalworking fluid should have high thermal conductivity, specific heat and heat transfer coefficient to improve heat dissipation.
Applications of Cutting Fluid
Drilling, broaching, milling and tapping with high-speed steel tools are typical examples of these operations where the use of cutting fluids is predominant. Another important application of cutting fluids is in operations where low surface roughness and tight dimensional tolerances are required.