What Are Cutting Fluids? | Types of Cutting Fluids | Uses of Cutting Fluids | Selection of Cutting Fluid

What Are Cutting Fluids?

Cutting fluids are liquids that are commonly applied while machining (or cutting) operation is taking place. The machining operation can be anyone, i.e., milling, turning, drilling, etc.

Sometimes a cutting fluid is also called a coolant, but this is incorrect. A cutting fluid performs many functions, and cooling the equipment and workpiece is one of them.

Cutting fluid is a fluid used primarily to remove heat generated during metal cutting & other machining processes. It is also used’s as a lubricant in some cases. They are also used to improve cutting conditions and tool life.

The cutting fluids reduce friction between the tool and the chip and between the tool and the workpiece. If the correct amount of cutting fluid is applied, heat can be removed as soon as it is generated. So cutting fluids is necessary to increase production efficiency.

Prior to the discovery of HSS, there was no problem in selecting the cutting fluid, and water was used as a coolant because machining was done at a very slow rate. But after the discovery of HSS, water was not appropriate because the heat generated during machining was high due to high-speed machining. Therefore, different cutting fluids were discovered & made for different machining processes & materials.

Cutting fluids can be in liquid or gaseous forms. It is mainly used in metal processes such as machining and stamping.

Cutting fluids are of various types such as oil, oil-water emission, pastes, gels, etc. The cutting fluid may be referred to as the cutting fluid, cutting oil, coolant, or lubricant, depending on the type of cutting fluid and its use. Cutting fluids can be beneficial for most metal and machining processes.

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Types of Cutting Fluids:

Cutting fluid is classified into the following types: –

#1. Straight Oil

Stroth oils are non-emulsifying. These oils are used without diluting them with water. The compositions of this type of oil are base minerals or petroleum oil. Examples of straight oil are paraffin oil, Naphthenic oil, vegetable oil.

In systems where environmentally friendly oil is required, vegetable oil is used because it is biodegradable. Straight oils are best for lubricating, but they cannot serve as a good coolant because they have very cool properties.

#2. Soluble Oil

Soluble oils are made by mixing mineral oil, water, & coupling agents. It provides good lubrication between water-inaccurate liquids. Soluble oils are used in the machining of both ferrous and non-ferrous metals when high cooling quality is required & chip bearing capacity is not very high.

This soluble oil works well in its diluted form and provides great lubrication in addition to heat transfer. Soluble oils are the most widely used liquids in the industry, and also they are very cheap.

#3. Mineral Oil

Mineral oils are typically found in high production machines that have high metal removal rates. They are used in heavy cutting operations as they have very good lubricating properties. A disadvantage of these oils is that they are corrosives and therefore are not used for copper or its alloys.

#4. Synthetic Liquids

As these are synthetic liquids, they do not contain mineral oil or petroleum. These are water-based liquids, and water provides very good cooling properties. The problem with synthetic fluids is that it is not a good lubricant and also causes corrosion.

Corrosion or corrosion can be prevented by adding corrosion inhibitors to synthetic liquids. Typically, synthetic fluids are used in grinding liquids.

#5. Semi-Synthetic Fluids

Semi-synthetic fluid is made from a combination of synthetic fluid and soluble oils. For semi-synthetic liquids, approximately 5 to 20% of mineral oil is emitted with water to produce microabrasion. The size of microalgae particles varies from 0.01 to 0.1 mm, which can easily transmit all light.

Semi-synthetic fluids have very good cooling properties and cost between synthetic fluid and soluble fluid costs. Some examples are molybdenum disulfides, graphite, wax stick, etc.

#6. Solid and Paste Lubricants

These lubricants are in the solids phase or as a paste. These lubricants are placed directly on the workpiece or tool. Some examples of this are molybdenum disulfide, graphite, wax stick, etc.

#7. Cutting Oil

Cutting oil is made by mixing minerals oil & fatty oil. It is used as both a coolant and a lubricant.

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Uses of Cutting Fluids:

The cutting fluid can be used for different purposes. Some of its uses are listed below:

• Used as a coolant:- The main task for which the fluid was discovered is to cool the equipment and workpiece. By cooling the equipment and workpiece, we can reduce tool wear, thermal expansion of the tool, and a good surface finish.
• Used for lubrication:- Cutting fluids are also used for lubrication. By lubricating, chips & other contaminants can be easily removed from the workpiece.
• Used for cleaning the machining area:- Cutting fluids are also used as a cleansing agent and remove dust near and inside the cutting area. This dust removal is important because dust can cause uneven bites.
• Is used to reduce friction:- The cutting fluid also reduces friction between the tool and the workpiece, which keeps the cutting forces down and also reduces heat generation.
• It is used to improve the surface’s finish by protecting the newly formed surface from oxidation and corrosion.
• It is used to prevent rust.
• This allows the use of higher cutting speeds and larger metal removal rates.
• It prevents the formation of built-up edges (BUE).
• It is also used to extract chips from the cutting zone.

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Selection of Cutting Fluid:

The choice of cutting fluid in machining processes depends on various factors. Cutting fluids are selected according to which the main factors are given below:

#1. Machining Process Type

Typically, more difficult machining processes more cutting fluids. Heavy cutting oil is required for heavy machining processes such as broking or screwing with a tap.

Heavy cutting oils should be used in horizontal broking, but in the vertical broking process, emulsions and solutions may be used. For the threading and drillings process, the cooling characteristics of cuttings fluids are more important.

#2. Workpiece Material

The next factor for the selection of cuttings fluids is the workpiece material. The cast iron and cast group of materials are brittle during machining, and therefore small chips are produced that do not cause too much friction. Therefore emulsion should be used as it increases the surface finish, and the concentration should be kept between 10 and 15 percent.

• For steel and stainless steel workpiece materials, high-pressure cutting oils should be used.
• For machinings of steel alloys, water-based cutting fluids are used because they are heat resistant & difficult to cut.

#3. Cutting Tool Material

Another’s a factor for the selection of cutting tool materials is cutting tool material. High-speed steel cuttings tools can be used with any type of cutting tool, but when the material is difficult to cut, the waterless cutting liquid is used with the HSS cutting tool.

For tungsten carbides, the cooling characteristics of cutting fluids are more important because higher heat is produced when it is used as a cutting tool material.

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Properties of Good Cutting Fluid:

• Cutting fluid should have good antivirus properties.
• It should not foam easily.
• It should be chemically neutral & should not harm the machine and operator.
• It must have high specific heat or high heat-absorbing ability to disperse the heat generated during machining.
• It should be transparent so that the operators can easily go through it in the cutting area.
• It should have good lubricating properties so that it reduces friction during machining.
• It should be nontoxic when it comes in contact with heating and should not create any toxic fumes.
• It should be odorless and should not cause any odor at high temperatures.
• It should have low viscosities so that it can flow easily over the workpiece.
• It should be non-corrosive for workpieces and machines.
• It should not glue parts of the machine.
• It should have small molecular sizes to allow it to penetrate the chip tool interface and spread rapidly.
• It should have a high flash point & should not burn due to heat generated during machining.

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Applications of Cutting Fluid:

Cutting fluid can be used for different purposes, and those are:

• As a Coolant.
• It is used to cool the cutting tool, chip, and job.
• As a Lubricant.
• Used for more effortless movement of the tool on the job and also reduce the cutting force.
• Used as Lubricant and Coolant.
• Cutting fluid can also be used for coolant & lubrication purposes like Fatty Oil.
• As a Flashing Action.
• To wash off chips, to get better surfaces to finish.

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Frequently Asked Questions (FAQ)

Cutting Fluids

Cutting fluid is a type of coolant and lubricant designed specifically for metalworking processes, such as machining and stamping. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, aerosols (mists), and air or other gases.

Type of Cutting Fluid

Types of cutting fluids:-

• Straight Oil
• Soluble Oil
• Mineral Oil
• Synthetic Liquids
• Semi-Synthetic Fluids
• Solid and Paste Lubricants
• Cutting Oil

What Is Cutting Fluid?

Cutting fluid is a fluid used primarily to remove heat generated during metal cutting & other machining processes. It is also used’s as a lubricant in some cases.

Cutting Fluid in Machining

A cutting fluid is a substance designed specifically for metal-working and machining processes that serve as both lubricant and coolant during these processes. This fluid is usually applied as the machining process is taking place. Cutting fluids may be applied by flooding, a fluid jet, mist spraying, etc.

Best Cutting Fluids for Metalworking

For tough operations such as tapping, threading, and broaching, a sulfochlorinated mineral-fatty oil is recommended for tool steels and high-strength steels, and a heavy sulfurized mineral-fatty oil or a sulfochlorinated mineral oil can be used for medium- and low-strength steels.

Cutting Fluids for CNC Machines

Cutting fluids play a crucial role in the performance and efficiency of CNC (Computer Numerical Control) machines. They are used to lubricate, cool, and remove chips during the machining process. Selecting the appropriate cutting fluid is essential for achieving optimal results and prolonging the lifespan of your CNC machine’s cutting tools. Here are some common types of cutting fluids used for CNC machines:

1. Soluble Oils: Soluble oils, also known as emulsifiable oils, are a mixture of oil and water. They provide good lubrication and cooling properties, making them suitable for a wide range of machining operations. Soluble oils are versatile and can be diluted with water to achieve the desired level of lubrication. They also offer some rust protection for machine components.
2. Synthetic Coolants: Synthetic coolants, also called synthetic cutting fluids or synthetics, are water-based solutions with additives to enhance their lubricating and cooling properties. They are formulated to provide excellent heat dissipation and chip removal. Synthetic coolants offer superior performance in terms of surface finish, tool life, and corrosion prevention. They are also known for their cleanliness and low foaming characteristics.
3. Semi-Synthetic Coolants: Semi-synthetic coolants, as the name suggests, are a blend of synthetic and mineral oils. These cutting fluids offer a balance between the performance of synthetic coolants and the cost-effectiveness of soluble oils. Semi-synthetics provide good lubrication, cooling, and chip evacuation while minimizing the issues related to foaming and residue buildup.
4. Straight Oils: Straight oils, also known as neat cutting oils, are undiluted mineral oils or petroleum-based fluids. They provide excellent lubrication and heat dissipation properties, making them suitable for heavy-duty machining operations. Straight oils offer high lubricity and are typically used in applications where extreme pressure and heat are generated. They may require additional equipment, such as a separate coolant system, to remove heat and chips effectively.
5. Vegetable-based Cutting Fluids: Vegetable-based cutting fluids, often referred to as bio-based or eco-friendly fluids, are derived from renewable resources like vegetable oils. They are an environmentally friendly alternative to traditional cutting fluids. These fluids offer good lubricity, cooling, and biodegradability. Vegetable-based cutting fluids are less likely to cause skin irritation or respiratory issues compared to some other cutting fluids.

Synthetic Cutting Fluids Vs. Water-Based Fluids

Synthetic cutting fluids and water-based cutting fluids are two common types of cutting fluids used in industrial applications. While both serve the purpose of lubricating and cooling during the machining process, they have distinct characteristics and advantages. Here’s a comparison between synthetic cutting fluids and water-based fluids:

1. Composition:

• Synthetic Cutting Fluids: Synthetic cutting fluids are oil-based fluids that contain synthetic additives. They typically consist of a water-soluble synthetic base oil, emulsifiers, corrosion inhibitors, and other additives to enhance performance.
• Water-Based Cutting Fluids: Water-based cutting fluids, as the name suggests, are primarily composed of water. They can be soluble oils, emulsifiable oils, or solutions with water-soluble additives.

2. Lubrication:

• Synthetic Cutting Fluids: Synthetic fluids offer excellent lubrication properties, which help reduce friction and tool wear. They form a protective film on the cutting tool and workpiece, minimizing heat generation and extending tool life.
• Water-Based Cutting Fluids: Water-based fluids have moderate lubrication properties, providing some level of protection to the cutting tool and workpiece. However, they may not offer the same high level of lubrication as synthetic fluids.

3. Cooling:

• Synthetic Cutting Fluids: Synthetic fluids have good cooling capabilities, effectively dissipating heat from the cutting zone. This helps maintain stable temperatures and prevents thermal damage to the tool and workpiece.
• Water-Based Cutting Fluids: Water-based fluids have excellent cooling properties due to the high heat capacity of water. They efficiently absorb and carry away heat generated during the machining process, helping to prevent overheating and prolonging tool life.

4. Rust and Corrosion Protection:

• Synthetic Cutting Fluids: Synthetic fluids typically provide better rust and corrosion protection compared to water-based fluids. They contain additives that form a protective barrier on the metal surfaces, guarding against corrosion.
• Water-Based Cutting Fluids: Water-based fluids offer moderate rust and corrosion protection. However, they may require additional additives or inhibitors to enhance their anti-corrosion properties.

5. Environmental Impact:

• Synthetic Cutting Fluids: Synthetic fluids may have a higher environmental impact due to their oil-based composition. They require proper disposal procedures and can contribute to waste generation.
• Water-Based Cutting Fluids: Water-based fluids are generally more environmentally friendly, as they are primarily composed of water. They are easier to handle, dispose of, and have lower potential for environmental harm.

6. Compatibility:

• Synthetic Cutting Fluids: Synthetic fluids are compatible with a wide range of materials and machining operations. They are particularly suitable for demanding applications, high-speed machining, and difficult-to-machine materials.
• Water-Based Cutting Fluids: Water-based fluids are also versatile and can be used for various materials and machining operations. They are commonly employed in general-purpose machining and applications where lubrication needs are not extremely demanding.

Environmentally-Friendly Cutting Fluids for Sustainable Manufacturing

Eco-friendly cutting fluids are highly biodegradable and have no adverse environmental impact [15, 16]. Some of the common vegetable-based cutting oils are cottonseed, groundnut, coconut, sesame, canola, and soybean [17–21].

Cutting Fluids Are Used to

Cutting fluids provide cooling at the cutting tool and on the surface of work piece, lubricate the tool-workpiece interface and evacuate chips from the cutting zone in the machining processes.

Cutting Oil Uses

What are Cutting Oils and What are They Used For? Cutting Oils, also commonly referred to as coolant, cutting fluid or cutting compound, provides lubrication and cooling during machining processes, rust and corrosion protection as well as aiding in chip removal from the cutting area.

Difference Between Cutting Fluid and Lubricant

The key difference between cutting fluid and lubricant is that cutting fluids can lubricate the interface between the cutting tool’s cutting edge and the chip, whereas lubricants can lubricate between hard materials by reducing the friction between the objects.

What Are the Types of Cutting Fluids?

• Soluble oils (emulsions) Soluble oils are stable emulsions formed by the addition of mineral oil to water in specified proportions (usually 1-20% of oil to water).
• Straight oils.
• Synthetic fluids.
• Semi-synthetic fluids.
• Cooling.
• Lubrication.
• Improvement of tool-life.
• Removal of chips.

Purpose of Cutting Fluid

Cutting fluids provide lubrication to the cutting tool and workpiece, which helps to improve the movement of the tool and reduce wear and tear on the machinery. Cutting fluids can be used as coolants, lubricants, and flushing fluids, making them a versatile solution for a range of metal cutting operations.

Different Types of Cutting Fluids

• Soluble oils (emulsions) Soluble oils are stable emulsions formed by the addition of mineral oil to water in specified proportions (usually 1-20% of oil to water).
• Straight oils.
• Synthetic fluids.
• Semi-synthetic fluids.
• Cooling.
• Lubrication.
• Improvement of tool-life.
• Removal of chips.

What Are Cutting Fluids Made Of?

Cutting fluid concentrates are comprised of base oil, esters and fatty acids, emulsifiers, rust protection, pH-regulating additives and anti-foaming agents. The properties of the emulsion can be altered and varied by changing the levels of the constituent components.

Application of Cutting Fluid

Cutting fluids are commonly used as a coolant, lubricant, and flushing fluid. As a coolant, cutting fluids are often applied to cool down the cutting tool and the workpiece. As a lubricant, cutting fluids are used to lubricate the tools and machinery, reducing cutting force and friction.

Properties of Cutting Fluids

The common properties of cutting fluids include high heat absorbing capacity, high flash point, non-corrosiveness, good lubrication properties, and odorless stability. Cutting fluids are known for their high heat-absorbing capacity, which helps to prevent the temperature from rising and causing damage.

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