Properties of a lubricant & its types|Coolant & its types

Hello friends, Today I am talking about Lubricant, in which we know in detail properties of a lubricant, different types of lubricant, method of lubrication, and also covers  some details about coolant.

Lubricant play very most important role in machinery by which any machine's life and efficiency increases. 

Here I also talked about some coolant which is used in manufacturing process like drilling ,cutting operation  etc. which is performed by a Drilling machine and Lathe machine .

In workshops and industries, different types of machines are being used to give required output. 

By the movement of two mating parts of a machine, friction is produced due to which, some amount of heat is generated and it also affects the efficiency of the machine.

So that, a process called lubrication comes into action which is employed to reduce the friction between two surfaces which are moving relative to each other like bearing.

In the similar way, in operation like cutting, drilling, etc. Two surfaces rub with each other, due to this, these surfaces are wormed out.

So to keep away the spoilage of tools, a process called cooling used which helps to cool the tools or their surfaces to prevent from any type of breakage.

The substance used in the process of cooling is called coolants.


A lubricant is a substance or elements, which is reducing the friction between two mating parts or surfaces.

properties of a lubricant

Purpose of using lubricant is as follows
  1.  It cools the moving elements.
  2. It improves the machine efficiency.
  3.  It aids in distributing the load.
  4.  It reduces friction.

Properties of Lubricants

The properties of a lubricant are following types
  • Oiliness
  • Viscosity
  • Viscosity Index
  • Flash Point
  • Fire Point
  • Pour Point
  • Emulsification
  • Specific Gravity
  • Acidity
  • Oxidation
  • Volatility


The term oiliness is related to a lubricating tendency that is wet and adhesive on a surface in which a thin layer of oil film is formed between two moving parts. So, the rest surfaces oily.

That means it is the capability of lubricant to maintained adherences in between the surfaces.


The viscosity is a measurement of the internal resistance of a lubricant that means heavy oil has high viscosity and light oil has low viscosity.

Viscosity is always inversely proportional to the temperature that means when temperature increases then viscosity decreases.

Viscosity is measure in terms of kinematic viscosity or centistoke.

Viscosity Index

It is the properties of a lubricant which is measure the viscosity of the fluid or oil with reference to temperature. 

That means when oil temperature increases or decreases then how much changes in viscosity of oil or fluid.

Flash Point

The flash point is the temperature at which, a lubricant start to converts into a steam or vapour.

Fire Point

It is a temperature point at which oil or lubricant tends to the vaporising.
Each oil or lubricant has a separate fire and flash point.

Pour Point

It is the minimum temperature at which the oil will still pour.

That means it is the lowest temperature at which flow of oil is ceases.


Emulsify means mixing two liquids together that are not usually mixed.

For example, when oil comes in contact with water, it is called emulsification.

Specific Gravity

It is properties of a lubricant at which its weight is compared with water at 30° F.


For lubricants, acidity refers to the presence of acidic components, the concentration of which is usually defined by the total number of acids. 

There should be no acidity in the oil.


Oxidation reduces the flow of oil when the lubricant makes contact with hot air. 

The formation of this oxide is prevented by adding it to the oil.


Volatility is a properties of a lubricant that defines its evaporative loss characteristics.

Properties of a good lubricant

So friends here we clearly know about properties of a lubricant now we know that what should be properties of a good lubricant.

Which is described in below
  1. A good lubricant oiliness should adhere adequately to surfaces to high pressures.
  2.  The viscosity of a good lubricant should not be changes or vary with the operational working temperature.
  3. Viscosity index of a good lubricant should be high.
  4. Flash and fire point temperature always above the operating temperature.
  5. For a good lubricating, poor point temperature always should be very low.
  6. For a good lubricant, acidity should be always negligible.
  7. Oxidation resistance for a good lubricant, should be always high.
  8. For a good lubricant, volatility should be always as possible as low. 

Types of Lubricants

Lubricants can be classified into three categories such as
  • Liquid Lubricants
  • Solid Lubricants
  • Semi-Liquid Lubricants

Liquid Lubricants

These are available in liquid form such as mobile oil, spindle oil, natural oils, mineral oils, semi-solid lubricants, liquid lubricants.

Liquid lubricants can be divided into four categories such as
  • Mineral Oil
  • Organic Oil
  • Synthetic Oil
  • Blended oil

Mineral Oil

It is a substance of petroleum. These oils contain the paraffin and naphthalene quality, that means stable with the high temperature. 

Organic Oil

It is a substance of the animals, vegetables, fishes.

It is conducted the alcohols and fat acids, For the heavy load, it is mixed with the mineral oil.

Organic oil is also known as the compound oil.

Synthetic Oil

It is a element of the polakaline glycol, silicon and silicon carbide.

This type of oil has a long life and quality is better so that, it used to the precision tools.

Blended oil

To make the heavy lubricant and increasing the viscosity, the fatty oil 5 to 20% is used, It called compound oil or blended oil.

Solid Lubricants

Graphite is a widely used solid lubricant. Another type of solid lubricant is soapstone, talc, Chalk, etc.

Semi-liquid Lubricants

Greases are semi-liquid lubricants with a higher viscosity than oils.

These types of lubricant used for slow speed and in high pressure operations like drawing process, rolling and also extrusion processes.

Methods of Lubrication

Depending on the physical properties of a lubricant, the following lubrication methods are distinguished.

  • Gravity Feed
  • Force Feed
  • Splash Lubrication

Different method of lubrication shown in figure and briefly explain bellow

properties of a lubricant
Lubrication Method

Gravity Feed

The gravity feed principle is used in the oil holes, sump and wick feed lubricators installed on the machines.

In doing so, the oil is poured into a bottle, placed high in the machine and used drop by drop using cotton.

In this type of gravity feed process, There are following types of  methods are applied
  1. Oil Cup
  2. Wick Lubricator
  3. Drip Feed Lubricator
  4. Lieuvain's Glass Bottle Lubricator

Force Feed

It is the process of supplying lubricant or coolant to any machine by hand or by machine power.

Like - Centrifuge pump

There are some methods of force feed processing
  1. Oil, Grease Gun and Grease Cups
  2. Pressure Feed by Hand Pump
  3. Oil Pump Method

Splash Lubrication

In this method, an annular oiler is attached to the shaft, which is immersed in the oil, and a stream of lubricant is continuously sprayed around the parts as the shaft rotates. 

The rotation of the shaft causes the ring to rotate, the oil adhered to it rises and flows into the bearing, and then the oil returns to the reservoir. 

The rotation of the shaft causes the ring to rotate, the oil adhered to it rises and flows into the bearing, and then the oil returns to the reservoir.


In the cutting operation, to keep cool the cutting tools, cutting pieces and cutting chips the cooling process is used. In this process the coolant is used.

Coolant (Cutting Fluids)

The medium, which is employed to remove heat from the tool point during a cutting operation, is called a coolant.

It performs the following functions
  1. Cool the cutting edge of the tool.
  2. Reduce friction between the tool and the job.
  3. Cool the job.
  4. Cause the chip to break.

Types of Coolants

There are many types of coolants discussed below
  • Air
  • Cutting Oil
  • Soluble Oil
  • Synthetic Coolant
  • Gaseous Fluid


Air coolant is normally used by those machines which are made up of cast iron. 

In those machines, for machining processes fan is provided with the engine or motor. So that, it provides the cooling.

Cutting Oil

It is used in machining, when machine works with hard metal at high speed, then oil is used in place of coolant such as kerosene oil, soluble oil, etc.

Soluble Oil

These are generally comprised of 60-90% petroleum or mineral oil, emulsifies and other additions. 

It is a mixture of mineral oil, fatty oil and emulsifier. In which general ratio of oil and water used as coolant is 1:5 to 1:80.

Synthetic Coolant

It is a compound of some chemical agents and water. The general ratio synthetic coolant and water used in 1:50 to 1: 250.

Gaseous Fluid

In the cutting operation, the mist is worked as the best coolant. There are used carbon dioxide, Freon and helium as a coolant in special conditions.  

So, here I discussed about properties of a lubricant and its types also covers some details about coolant.

I hope you guys like this topic if any query you can ask me through comment.

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