What are Cutting Fluids? Definition, Function, Types, Application Technique

In this article, we will learn what are cutting fluids, along with its basic definition, function or purpose, types, application techniques, safety measures, etc. Let’s explore!

What are Cutting Fluids? Definition

Cutting Fluids Basics

Let’s try to understand the basics of cutting fluids. When we talk about machining or cutting, the rising temperature, and deformity grab our attention. This deformity can quickly occur to either the workpiece or the cutting tool used.

To remove this bottleneck and keep our cutting tool and workpiece safe, we use cutting fluids. The use of cutting fluids comes a long way back. We can say that it has been in society almost for the last 200 years. In the beginning, numerous things were used as cutting fluids, such as oils that help in lubrication and cooling the tool.

Numerous substitutes such as animal fat, lard, and whale oil are being used as cutting fluid lubricant substitutes. As we have advanced, the need for cutting fluids increased and became more complex. Nowadays, the cutting fluids come with a par class mixture of chemical additives, formulated water, and lubricants that help achieve the industry’s tool performance.

Here we will provide adequate information about the cutting fluid right from the fundamental aspect. Let us start with the core definition of cutting fluid:

Cutting Fluids Definition

Cutting fluids are generally the fluids that are used for providing numerous benefits to the workpiece and the machine tools. Cutting fluids can be defined as the fluids that help in providing better cutting conditions. The following are the core working parameters that can vastly be affected by the cutting fluids:

  • Machining operations
  • Shop productivity
  • Tool life
  • Quality of work

The role of cutting fluid can be critically understandable as these play an important role in core machining and shop works but also help us in waste management and disposal. These two are the main factors that are to be considered in every manufacturing or machining industry. As we know, cutting fluids also helps in waste management, but the same disposal after use is crucial as it is quite lethal for the environment.

What is the Purpose of Using Cutting Fluids?

It is essential to understand the core purpose of cutting fluid. The use of cutting fluid helps in two major aspects that are a tool and the workpiece. Apart from that, the following five points can clear the air around the core purpose:

Lowering the temperature

The use of cutting fluids decreases the temperature that generates due to the increase in the friction between the workpiece and the tool. It decreases the temperature by minimizing the heat at the time of cutting operation. The core purpose coincides with this: the tool life can increase, and one can easily attain a good surface finish.

Decreasing the friction while cutting or machining

The coolant of cutting fluids can quickly reduce the friction that is the main cause of heat generation. With the help of excessive pressure of coolant, the fluid chips can be removed effectively.

Reducing the thermal breakage and tool wear

With cutting fluid, we can quickly diminish the tool or workpiece’s thermal breakage. It also helps in restricting the wear of the tool. With the above three main points, it is clear that the cutting fluids have vivid functionalities, while the main concern regarding these is the proper management and the effective technique for coolant use.

Environmental safety is one of the concerns as these cutting fluids are equipped with some lethal chemicals that can harm in the most dangerous ways. With the proper usage, we can easily fulfil some of the core responsibilities:

  • With proper management, we can use the cooling fluids effectively
  • Proper management of cutting fluids decreases the overall costing and increases productivity.
  • Helps in manufacturing of quality products
  • It also helps in providing an apt and safer work environment
  • Ultimately also helps in decreasing environmental liability.
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Elaborative discussion about core functions of cutting fluid

With the proper understanding of the cutting fluid, one can use it for maximum efficiency. The following are the elaborative discussion that provides an all-round idea about the cutting fluid or coolant functionality.

Calibration of temperature

It is evident that wherever friction comes into play, it generates heat, and thus the temperature also increases, which has a definite place in the tool wear. It is vital to decrease the tool temperature as it provides smooth machining and helps attain great tool life. When applied to the machining operations, the cutting fluid helps remove the heat away from the workpiece or cutting tool focus.

Cleaning action for the particulates

One of the significant secondary functions of these cutting fluids is to remove metal and chips particulates that come due to the machining process. It is essential to flush away the cutting chips as it quickly makes the finished surface marred.

Not only the normal cleaning action but the cutting fluid also helps in constraining the built-up edge. The built-up edge formation effectively causes the friction to increase and may change the whole tool geometry. It affects the end product quality, which should not be compromised at any cost.

Protection against corrosion

In addition to the core properties, the cutting fluids also provide corrosion protection as it is evident that the freshly machined or cut materials are more prone to rust. This is because they are not equipped with any of the protective coatings after machining.

An ideal cutting fluid contains rust preventive properties that help minimize damage to the machine parts and the workpiece. Additionally, there is somehow the cutting fluid that provides a protective layer after cutting of the ferrous metals.

Controlling the rancidity

Being rancid is quite common as most of the coolants are equipped with a terrible odor. This is mainly caused by microscopic organisms or bacterial that eventually grew within the oil. Due to this, the chance of increasing toxicity also increases, which is not a good practice for the environment as we have to dispose of these coolants. The toxicity of the coolant cannot be ignored as it can cause lethal problems to the environment.

Viscous and transparent

In some of the machining operations, the need for the coolant fluid to be transparent is necessary. It helps the operators get a holistic idea about the cutting of the workpiece and helps in keeping a check on the machine tool.

Viscosity plays a significant role in the cutting fluid performance. These also help attain transparency that effectively impacts fluid life, product quality, and overall productivity. With these, it is clear that we need to use some of the preferable techniques for cutting fluid applications. Further in this article, we are going to discuss the same.

Applications Techniques of Cutting Fluids

Being one of the dangerous things equipped with different chemicals, it is necessary to use the cutting fluids effectively. There are some specific ways or techniques that can help in getting the holistic idea. These application techniques are mainly of three kinds:

  • Manual application technique
  • Flood application technique
  • Mist applications technique

Manual application technique

In this technique operator simply uses a container in which the cutting fluid is filled. They apply the cutting fluid from that container. This is among the oldest techniques, which is pretty cost-effective. However, this technique is equipped with inconsistency, due to which it has limited usage.

Flood application technique

This is among the preferred application technique of the cutting fluid in which the cutting fluid is delivered with the help of a hose, nozzle, or pipe system. In this, the fluid is directed to the tool with excessive pressure. This pressure helps in attaining maximum results. In this technique, it is mandatory to check the fluid stream’s direction, shape, and pressure, which helps attain par level performance and productivity.

Mist application technique

The process of blowing the atomized particles of the cutting fluid to the tool or workpiece is known as mist application. This application technique requires proper ventilation that helps in providing a safe environment for working. There are some parameters such as direction, and pressure plays a vital role in the practical application.

Apart from the manual system, the metalworking fluid application technique uses a specific tool system and a central reservoir system. The cutting fluid is stored in a central reservoir system while the machine tool system helps in the whole process of application.

This includes a pump, delivery piping, fluid collection unit, fluid storage sump, return system, and filter that help in cleating the contaminants. In this, the coolant has a circulating action from the machine sump to the machine tool. The central reservoir contains a high amount of cutting fluid that is engaged in all the circulation work.

Types of Cutting Fluids with Pros & Cons

The types of fluids are available based on concentration. This concentration is either equipped with an oil base or chemical ingredients. Here we will discuss different kinds of cooling fluid with their effective pros and cons. With this, we will get an idea regarding the usage and effectiveness of the cooling fluid used for different purposes.

Oil-based cutting fluids

The most common of the cutting fluids comes with a concentration of oil. Mainly petroleum is the oil that constitutes massive volume proportion in these cutting fluids. There are three kinds of oil-based cutting fluids. The following are the brief description as well as the usage with pros and cons:

  • Straight oils
  • Soluble oils
  • Ag-based oil

Straight oils cutting fluids

Straight oils are the cutting fluid that does not contain water; it mainly contains oil, minerals, and petroleum. Numerous additives are present in the straight oil that helps in improving the core properties. Here these additives are not apt for light machining of ferrous and non-ferrous materials. Straight oils are mainly used for heavy-duty applications. The additives can provide a protective coating on the cutting tool and workpiece, making it quite adequate for the machining operation.

These can also handle the maximum amount of fine cuts, which is a much-needed factor for heavy-duty applications.


  • The primary benefit of straight oils is the optimal lubricity it provides. It helps in getting the cushioning effect between the cutting tool and workpiece.
  • The straight oil cutting fluid is useful for those machining operations where there is low clearance.
  • Where there is a need for a high-quality surface finish, we use straight oils.
  • The honing operation can also be attained with straight oil cutting fluids.
  • Straight oils effectively provide rust prevention, low maintenance and do not contaminate with bacterial or other impurities.


  • It has a high risk of heat dissipation and is also fire-prone.
  • With straight oils, it is likely to get more smoke or mist that critically makes the work environment unsafe.
  • These are used for low temperature and low-speed operations that make them inefficient and cause productivity loss.

Soluble oils

The soluble oils are also known as emulsifiable oils, water-soluble oils, or emulsions. These are equipped with 50-80% of mineral oil or petroleum. The soluble oils generally remain in concentrated form, which is mixed with water for further use.


  • Soluble oils provide effective and improved cooling properties that act as a good lubricant. This is because of the effective blend of water and oil in the soluble cooling fluids.
  • It also provides protective oil film to the machine tools.
  • These are effective for light and medium machining operations that help ferrous and non-ferrous machining or cutting operations.


  • Due to the presence of water, the probability of rust is prominent.
  • Rancidity and bacterial growth also start due to the presence of water-insoluble oils.
  • The maintenance cost associated with soluble oil is relatively high.
  • The high amount of oil content makes it quite challenging to clean the workpiece with this cooling fluid.
  • The probability of misting also occurs due to the use of these kinds of cooling fluids. It makes the work area dirty as well as unsafe.

Chemical-based cutting fluids

The chemical-based cooling fluids have been quite efficient and accepted for different usages for quite some time. These are pretty stable and equipped with emulsions in which the ingredients contain a small proportion of oil.

Due to this, the solubility of the cooling fluid is high with water. The compounds present in the chemical-based coolant helps to provide a protective film that keeps the workpiece safe from welding while the machining operations occur.

There are some of the compounds that can easily reduce heat generated while grinding and cutting operations. There are mainly two types of chemical-based cooling fluid, synthetics and semisynthetic. These are classified based on the compounds this cooling fluid contains. Here we are going to discuss both of them.


These are cutting fluid types which are not equipped with mineral oil or petroleum. The synthetics are the concentrate that gets mixed with water and ac as a cutting fluid. These are capable of providing high cooling to the tool or workpiece.

These are effectively preferred for surface grinding that includes different kinds of operations. The core ingredients of synthetic also contain nitrites and amines that provide effective functionality against rust. The concentrating contain phosphates which are water softening agents.


  • It can effectively provide rancidity control for a longer time.
  • The synthetics are safe as they have the properties that make them non-toxic, non-smoking, and non-flammable.
  • It provides effective corrosion control
  • It comes with optimal cooling capability.
  • The misting problem in synthetics is relatively low.


  • In the high agitation conditions, the synthetics are more prone to generate foams as well as mists.
  • It can cause several safety issues, such as dermatitis and misting.
  • These are more susceptible to be get contaminated by other fluids such as lubrication oils.

Semi synthetics

These are also known as semi-chemical fluids, which are mainly a mixture of synthetics and soluble oils. It contains 3 to 30% mineral oil diluted with water and semisynthetic materials such as water and emulsifiers. In addition to these, it also contains corrosion inhibitors, wetting agents, and biocides.


  • These are apt for providing lubricity to the workpiece that helps in heavy-duty applications.
  • It has optimal cooling and wetting properties, making it quite good for working with faster feed rates and excessive speed.
  • The low viscosity of these semisynthetic helps in the comparatively better cleaning operation.
  • It can easily cater to the problem of rancidity and keeps a check on bacterial growth.
  • It provides a low level of smoke and oil mist.
  • It comes with longevity and corrosion-resistant properties.


  • The hardness property of water makes it quite prone to hard water deposits.
  • Comparatively less lubrication than soluble oils due to foaming function.

How to Choose an Efficient Cooling Fluid?

The selection of an efficient cooling fluid can be a cumbersome process. The cutting fluid selection is based upon different aspects such as applications, pros, and cons. These aspects should be considered while selecting one with some of the subsidiary ones, such as supplier information, product history, ingredients list, etc. however one of the effective parameters that help choose the cooling fluid is used only. The following are some of the factors that should make the selection easier:

  • Cost associated
  • Life of the cutting fluid
  • Fluid properties with workpiece and tool
  • Machining parameters such as feed, depth, and speed
  • Mechanical properties of the material to be machined
  • Maintenance and quality of the cutting fluid
  • Specified temperature range for the cutting fluid
  • The concentration of the cutting fluid
  • pH range of the cutting fluid
  • Ease of disposal or recycling
  • Storage options

The above parameters play an essential role in the selection, though some other properties also come into vicinity, such as fluid’s versatility, formulations, performance, etc.

Tips for Safety while using coolant fluids

As we know, coolants are pretty lethal and toxic as they use different kinds of chemicals. It is prescribed to use these cooling fluids with utmost precautions. Here we are providing some of the properties that can be lethal for humans working around. It is better to keep a check on these:

Toxicity of the cooling fluid

In most of the machining operations, the cooling fluids used are of a highly toxic composition. Due to this, the fluid acquires rancidity or contamination. This can be toxic to the operators or the human in contact as it may come into exposure through inhalation or skin absorption. Respiratory problems are quite prone if these cooling fluids are not used appropriately.


The machining operations generate a high amount of heat that causes the cutting fluids to ignite or smoke. It is mandatory to check on this property as it can cause substantial damage to the body if inhaled. To mitigate the risk of this problem, it is prescribed to use an appropriate mask that can help cater to this problem to the maximum extent.


Where the use of cutting fluid comes through the misting application, the probability of inhalation hazard becomes prominent. This can be catered to by providing coating equipment to help the operator be at a safe place. The core solution for the above safety points is to prepare the work area by considering the coolant flow and usage. It is prescribed to use all the personal protective equipment while working amidst the coolant.

Practical Storage of Cooling Fluids

While storing the cooling fluid, it is necessary to keep them safe as they are equipped with lethal ingredients. The following are the steps through which we can keep cooling fluids effectively:

  • Keep the cooling fluids stored in sealed and original containers.
  • These cutting fluids should be stored in the conditions which should be frost-free, dry conditions.
  • These should also be kept away from direct sunlight as a change in temperature can be lethal.
  • When opened, adequate safeguarding of the containers is considered as they can be kept away from dirt, dust, etc.
  • Routine checkups and interim checkups should be checked continuously for contamination. If found, it should be cleaned.

Monitoring Methods for Checking of Cooling Fluids

For storing and there are some of the methods that can be vital. In this, the monitoring keeps a prominent place. Some effective monitoring methods can be used for safekeeping and getting efficient usage.

Visual checks: For any kind of testing the visual checks are the best practice that should be performed daily. In this, there should be prerequisites that keep the fluid in apt condition. It is preferred to keep the check of cutting fluid level in the centralized tank.

pH value measurement: A pH measurement is among the routine testing that should be done weekly. The easiest way to use these test strips is by color indication. These are the safest and easiest ways to check and do not require any kind of specific calibration.

Concentration measurement: The soluble cooling fluids or other synthetics need to be diluted with water. It is preferable to test the concentration weekly or daily. The highly stressed machining operations need an adequate concentration of cooling fluid.

This helps in attaining machining efficiency and also helps in providing cost-effectiveness. One of the most common equipment that can be used for the concentration measurement is the refractometer.

Nitrite and nitrate content check: The monitoring of nitrite content is quite effective for measuring the cooling fluid concentration. The nitrite contents help in attaining optimal concentration that makes the cooling fluid quite powerful for all purposes.

Apart from the nitrite content, the nitrate content is also important. The nitrate originates when the cooling fluid is mixed with water which can be checked by test strips specially manufactured for this testing.

Water hardness level: One of the mandatory parameters to check is the water hardness level as it defines the mixture effectiveness. This can also be done through simple and easy-to-use strips. It is quite mandatory as the high water hardness level can result in the cooling liquid evaporation loss.


Some efficient materials play a significant role in machining or cutting; however, these are equally dangerous. Cooling fluid is among those which help to mitigate the wear and tear of the tool, but it also harms the environment. The core properties of the cooling fluid help in attaining maximum life with optimum productivity.

In this excerpt, we have dealt with all the information related to cooling fluids. The introduction to the different types with safety measures while using the cooling fluids will be of immense help. We will elaborate the same with more information regarding the cooling fluid in our next article.


Hello Everyone! We, Rituparna Guha & Firan Mondal, are delighted to present our Mechanical Engineering articles. We will capture all types of articles and try to explain in the simplest way with a lot of diagrams! Happy Reading....

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