Thursday, 12 October 2017

Difference Between Sag Mill vs Ball Mill

Today we will learn about difference between sag mill vs ball mill. A mill is a machine by which solid or hard materials are broken into smaller pieces by means of grinding, crushing or cutting. This commutation is an essential part of many processes. Various kinds of mills are there with which different material processing takes place. The basic principle of mill machine is that when any solid substance goes under influence of mechanical work on it, that substance breaks into small pieces and it changes in grain-like structure.  Grinding can be also termed as Milling. In engineering, Grinding is used to enhance the surface area of any solid material.

 In ancient time, the mills were operated with muscle power (by hands), water animals and wind. They were totally based on the mechanical energy by natural resources and living beings.There are many types of mills which are used in the grinding industries. Today we will discuss about two important mill, sag mill and ball mill.

Sag Mill vs Ball Mill:

Semi-Autogenous Grinding Mill – SAG Mill:

SAG is the abbreviated form for Semi-Autogenous Grinding Mill. This type of Mill is used for grinding large fragments into small pieces. Pieces are then used for further processing. The SAG mills are generally used in pre-processing of any type of material in grinding process. SAG mills are also known as first stage grinders.  These heavy output SAG mills are usually powered by electricity. As requirements and needs in grinding field are enhanced. Improved SAG mills came in trend, which gives highly rated production. These mills are one of the most used and necessary equipment in grinding.

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SAG mill make use of steel balls included with some large and hard rocks for grinding. These mills utilize the balls in making the large fragments of materials broken into pieces. The ball charge of a SAG mill is about 9% to 20%.This process takes place inside the large rotating drum of SAG mill which is filled with balls partially. Interior of the drum uses the lifting plates. These plates inside the drum are responsible for picking the grinding material up to fall down again throughout the rotations. Repeated collisions between the steel balls and raw materials (ore), divides the material into finer and smaller pieces. This whole process takes place inside the large drum of SAG mill.

SAG mills are very important equipment of industrial mining. SAG mills are commonly used in mining fields. From mined coal, it separates out some precious metals. In the mining, some precious metals found are like gold, silver, nickel, and copper etc.   

Ball Mills:

Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics, small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29% to 30%. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness. The internal machinery of ball mill grinds the raw material into the powder-like material, And if extreme fineness and refinery are required then rotation go on continue.

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In the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.



SAG mill is the primary tool for grinding. SAG mill is used before the other mills.

Ball mill is a secondary, and it is used after the SAG mill.


SAG mill breaks the raw material into pieces for the further grinding.

Ball mill is used to grind the pieces of raw material into powder-like structures.


It does not create pulverized form of matter.

It creates pulverized form of matter.


SAG mill used for separating out the precious metals from mined coal

Ball mill is used to the production of Portland cement.


It uses about 10 – 20 % of metal balls into the cylinder.

It uses about 30-40% metal ball.

This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, don't forget to share it on social networks. Subscribe our website for more informative articles. 

Tuesday, 10 October 2017

Basic Introduction of Various Types of Milling Cutters

Today we will learn about types of milling cutters used in mechanical industries. Milling machine is a versatile machine on which we can perform most of machining operations. It is used to machine various shapes and size. Milling cutters are used to perform these operations. There are various types of cutter which are responsible for proper machining on milling machine. A small description of all of them are given below. 

Types of Milling Cutters:

1.End mill:

Types of Milling CuttersIt has both side teeth so it can be very successfully used in drilling operation. The word "end mill" is generally use to refer flat bottom cutters. The basic difference between drill bit and end mill cutter is that the drill bit can cut only in axial direction but this cutter can cut in all directions. This cutter has one or more flutes and mostly used in end milling operation. It is made by High speed steel or harder material.  This cutters mainly available in two types. The first one is known as center cutting in which the cutter has cutting edges on both the side and the other one is non center cutting edge in which the cutting edge is only in one side.

2.Roughing end mill:

Types of Milling CuttersRoughing end mills are also knows as "rippa" cutters. This cutters gives superlative performance in hardest operating condition. As the name implies it is used to remove large amount of material. This kind of cutter utilizes a wavy tooth from. These cutters forms very small chips which results rough surface finish. 

Some features of Rough End Mill Cutter are
  • Optimum performance 
  • Super Quality 
  • Anti-corrosive
  • High straight

3.Ball nose cutters:

Types of Milling CuttersBall Nose Cutter is manufactured from qualitative carbide rods. As the name implies this cutter has ball like shape at its nose which make it able to cut three dimensional shapes very effectively. 

The main advantages of ball mill cutters are:
  • Sturdy nature
  • Low maintenance
  • Rust resistance
  • Longer life service
  • Easy to use

4.Slab mill:

Types of Milling CuttersThis type of cutter is best in quality and can be bought from market with sharp edges. Moreover to this, these milling cutters are light in weight and can be used safely for longer years. This cutter is used to remove large material from a slab or machining a large surface. It can be used with both horizontal and vertical or universal milling machine. 

Various features of this cutter are:
  • Available in different sizes.
  • Hassle free installation.
  • Sharp edges.

5.Side & face cutter:

Types of Milling CuttersSide or face cutters are manly used to cut slot. This cutter has teeth both its side and circumference. It is available in varying diameters and widths depend on application.

6.Hob cutter:

Types of Milling CuttersHob is machine process of gear cutting. A cross section of the cutter tooth will generate the require shape on the work-piece. Hob cutter is specialist milling machine which is widely use in automobile industry. It is manufactured from prime grade material which insure high durability and functionality. These are manufactured with quality control process. 

7.Face mill:

Types of Milling CuttersAs the name implies, this tool is used to perform facing operation on any work piece. Facing is an operation in which large surface area machined to create large flat area. This tool has large diameter which is used to perform a facing operation. This device is manufactured by top quality component which ensure its high tensile strength robustness and maximum durability. Mostly 45 degree lead angle cutters are used for this purpose. 

There are some feature of this cutter:
  • Dimensional accuracy
  • Corrosion Resistant
  • High strength
  • Robust Construction
  • Abrasion Resistant 

8.Fly cutter:

Types of Milling CuttersIt is a cutting tool set transversely and revolving with the arbor of a lathe and acting upon work fed into its circular path.A fly cutter is composed of a body into which one or two tool bits are inserted. As the entire unit rotates, the tool bits take broad, shallow facing cuts. Face mills are more ideal in various respects , but tend to be expensive, whereas fly cutters are very inexpensive.

9. Woodruff cutter:

Types of Milling CuttersWoodruff cutters are used to make the seat. It is slightly hollow ground on the sides for relief and the teeth are not side cutting. The teeth come in both straight and staggered varieties. These qualitative cutters are widely use in order to make key seats in shaft of various shapes and sizes. 

Here are some feature about Woodruff Cutter:
  • High performance
  • Long service life
  • Ease of use

10. Hollow mill:

Types of Milling CuttersHollow milling cutters, more often called simply hollow mills, are essentially "inside-out end mills". They are shaped like a piece of pipe, with their cutting edges on the inside surface. They are used on turret lathes and screw machines as an alternative to turning with a box tool, or on milling machines or drill presses to finish a cylindrical boss. 

This is all about types of milling cutters. If you have any query regarding this article ask by commenting. If you like this article, don’t forget to share it on social networks. Subscribe our website for more informative articles.

Saturday, 7 October 2017

Difference between Gauge Pressure and Absolute Pressure

Today we will learn about difference between gauge pressure and absolute pressure. Pressure is defined as a normal force exerted by a fluid per unit area. It is defined only in liquid or gas state. In the solid state the normal force per unit area is called stress. SI unit of pressure is Pascal. One Pascal is equal to one newton per meter square pressure. MTS unit of pressure is KG/cm2.  Sometimes pressure is measure in respect of water column. Ten meter water column (mmwcl) is equal to one KG/cm2 pressure.

These all are small unit of pressure. The atmospheric or large quantity of pressure is measured in bars where one bar is equal to 100000 Pa pressure. One bar is also defined as 1.019 Kg/cm2 pressure. The standard value of atmospheric pressure is one bar.                                                 

According to the measurement pressure can be divided into two categories. The first one is known as gauge pressure and other one is absolute pressure. We will learn the difference between them in detail.

Difference between Gauge Pressure and Absolute Pressure:

Difference between Gauge Pressure and Absolute Pressure

Absolute Pressure:

The actual pressure at a given position is called the absolute pressure and it is measured relative to absolute vacuum. One concept remembers in mind that to measure any quantity we required a base line with respect we are going to measure it.

To learn this concept supposes we need to measure distance of Bombay. Distance can be measured in meter. Can we measure distance of Bombay by this input? Obviously your answer is no because we need a reference from which we want to measure distance. Now suppose we need to measure distance of Bombay from Delhi. Now we are able to measure this distance in some meters or kilometers.

Similarly pressure cannot be measured without a reference. When we take vacuum or no pressure condition as reference the measured pressure is called absolute pressure.

Gauge Pressure:

When we take atmospheric pressure as reference to measure pressure of any system, the measured pressure is known as gauge pressure. Most of pressure devices work in atmospheric condition always measure gauge pressure. We can convert this gauge pressure in absolute pressure by adding atmospheric pressure in gauge pressure.  

P (absolute) =  P (Gauge) +  P (Atmospheric)

Most of gauge read zero in atmosphere but there is some atmospheric pressure. They read atmospheric pressure as absolute zero pressure. Pressure below atmospheric pressure is called vacuum pressure and is measured by vacuum gauges that indicate the difference between the atmospheric pressure and absolute pressure.

P (vacuum) = P (Atmospheric) – P (Absolute)

This is all about gauge pressure and absolute pressure. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on social networks. Subscribe our website for more informative articles. 

Sunday, 17 September 2017

Thermal Power Plant : Principle, Parts, Working, Advantages and Disadvantages

Today we will learn about thermal power plant, its main components along with working and its advantages and disadvantages. Steam turbine power plant which is sometime known as coal based power plant or thermal power plant, is a major source of electrical energy for any country. This power plant basically runs on Rankine Cycle.

Thermal Power Plant:

Basic Introduction or Principle:

We all are aware with the term "Generator". A device which converts mechanical energy into electrical energy is known as generator. This generator makes rotate with the help of some kind of external energy. When this energy extract from the energy of steam, the plant is known as steam power plant.

Thermal Power Plant : Principle, Parts, Working, Advantages and Disadvantages

A simple steam plant works on Rankine cycle. In the first step, water is feed into a boiler at a very high pressure by BFP (boiler feed pump). This high pressurized water is heated into a boiler which converts it into high pressurized super heated steam. This high energized steam passes through steam turbine (a mechanical device which converts flow energy of fluid into mechanical energy) and rotate it. Owing to extract full energy of steam, three stage turbines is used which is known as LPT (Low pressure turbine), IPT (intermediate pressure turbine) and HPT (High pressure turbine). The turbine shaft is connected to the generator rotor shaft which makes rotate the generator shaft and produce electricity. In this process the steam loses its energy. This low pressurized saturated steam further passes through condenser where it converts into water. This water further passes through BFP and boiler and completes the cycle. This cycle continuously run to produce electricity.
Now we describe each component of thermal power plant in detail.

Construction of steam power plant:

Any steam power plant can be grouped into following section.

Thermal Power Plant : Principle, Parts, Working, Advantages and Disadvantages

Coal Handling Plant:

Coal Storage:
The place at which coal stored is known as coal storage. The coal initially received by mines is stored in proper place.

Coal from coal storage sends to bunkers. It is a container which is upper side of mill and used to continuously provide coal for mill machine. The minimum capacity of bunker is around 10 times of mill capacity.

Coal from the bunkers send to the feeder which provide coal to mill machine. The main reason to use feeder between bunkers and mill machine is that if we directly send coal to mill, it can damage the internal part of machine due to tones of pressure applied by the coal.

Mill Machine:
Coal does not directly used into boiler. The place where the coal is converted into pulverized form is known as mill machine. This pulverized coal sends to classifier from it.

Classifiers are used to separate pulverized and non-pulverized forms of coal. It sends pulverized coal to furnace and non-pulverized coal to mill machine.

Air Handling Plant:

PA Fan:
PA fan is primary air fan. This is used to transport pulverized coal to furnace. It also used to remove moisture contant from pulverized coal.

ID Fan:
ID fan means induced draft fan. This fan is used to suck the exhausted flue gases from the boiler and send it to atmosphere through chimney.

FD Fan:
FD means forced draft fan. It is used to provide air or we can say oxygen for proper burning of coal into the furnace. It provides hot air into the furnace.

Air Preheater:
It is a heat exchanger which transfer heat from exhausted flue gases to incoming PA and FD air. 

ESP (Electrostatic Precipitator):
This device is situated between Id fan and boiler exhaust and used to detect and block ash particles from flue gases and control the pollution being created by it. 

Chimney is used to create natural draft for exhausted flue gases. One chimney is used for two units. 

Boiler Section:

Economizer is the first component of boiler section. As the name implies, economizer is used to increase the efficiency of steam power plant. It is used to heat water upto saturation temperature. It extracts heat from exhausted flue gases and used it to heat water. It sends water to the boiler drum.  

Economizer sends water to the Boiler. Boiler is the main part of any thermal power plant. It is used to convert water into steam. In any steam power plant water tube boiler is used. It contains furnace inside the boiler shell. The Coal burns into this section. Drum is major part of steam power plant boiler. It is situated top of the boiler and used to separate water from steam. Steam from boiler section sends to super heaters.

Super heater:
The efficiency of thermal power plant is directly connected to the temperature of the steam. The boiler creates low temperature steam which is not so economical for any power plant. So a super heater is used to heat the steam again. The temperature of the steam is limited at 550 degree centigrade because the turbine material can’t sustain temperature above 600 degree centigrade. The steam from the super heater sends to high pressure turbine. 

Re heater:
When the steam expands into high pressure turbine, both its temperature and pressure get down. If this low temperature steam directly sends to IP turbine, it creates less power. To increase the power of the plant there is an arrangement  to send exhausted steam from HP turbine to Re-heater where it heated and get the initial temperature which is about 550 degree centigrade. 

Turbine Section:

Thermal Power Plant : Principle, Parts, Working, Advantages and Disadvantages

High Pressure Turbine:
The steam from the super heater sends to HP turbine. All the three turbines are connected to same shaft which is further connected to the generator shaft. The HP turbine works around 150 Kg/cm2 pressure and 550 degree centigrade temperature. It is smallest among all turbines.

Intermediate Pressure Turbine:
As the name implies it works at intermediate pressure which is around 70 Kg/cm2. The steam from the Re-heater sends to the IP turbine at around 550 degree centigrade where it expands and generates power.

Low Pressure Turbine:
This is the main power generator. It generates around 40 percent of whole power. The steam from IP turbine directly sends to LP turbine where it expand and rotate the turbine. It is biggest part of turbine section.  

To increase the efficiency, some amount of steam is extracted from both HP section exhaust and LP section exhaust. This extracted steam is used to heat water before send to economizer.

Condenser Section:

In a thermal power plant, to complete the cyclic operation, we need to send water again to the economizer at high pressure. Steam exhausted from LP turbine is not in condensed form and it is not economical to compress the steam at a very high pressure around 150 Kg/cm2. So a device is needed which can condense the steam into water. This device is called Condenser. Condenser is also a heat exchanger in which the cold water runs into tubes and steam flow from shell. The cold water extracts heat from steam and convert it into water. Condenser works at vacuum pressure which is around -1 Kg/cm2. It is due to create pressure difference between LP turbine exhausted steam and condenser which is required for proper flow of steam in it. The condensed water sends to a container which is named as Hotwell.

Condensed Extractor Pumps (CEPs):
The condensed water extracted by the pumps and send to LPH.

LPH (Low Pressure Heater):
The water collected from the condenser is at low pressure. To increase the efficiency of the plant this water is heated by the extracted steam from LP turbine.

The water collected from condenser has some dissolved gases like oxygen. This water can't directly send to boiler and turbines. it can cause of corrosion. To decrease the possibility of corrosion these dissolved gases should be removed from this water before converted it into steam. This work is done by Deaerator. Deaerator heat the water at some extant at which the dissolved gases converted into gases form and removed from water.

Feed Water Pump or Boiler Feed Pump:
BFP are centrifugal pumps which are used to increase the water pressure upto 150 Kg/cm2 and also send this water at economizer.

HPH (High Pressure Heater):
The pressurized water forced by BFP passes through high pressure heater which heats this water at some extent to increase the efficiency of plant. The steam extracted from HP exhaust is used to heat this water.

Cooling Tower:
Cooling tower is used to provide cold water for condenser tp condense steam into water.

Generator Section:
The turbine shaft is connected to the generator which rotates the rotor of the generator and produce electricity.

For the cold starting, the turbine does not rotate due to high inertia.  Exciter is used to rotate the turbine in the initial run.

Working of Steam Power Plant:

Now we have discussed about main components of thermal power plant and their uses. These all components work together to produce electricity. Its working can be summarized into following point.

Thermal Power Plant : Principle, Parts, Working, Advantages and Disadvantages

  • In the starting of the plant, pulverized coal from mill machine supplied to the boiler furnace by PA fan. FD fan provides desire oxygen for proper burning.
  • DM water is supplied by the Boiler feed pump to economizer.  This water achieves around 165 Kg per centimeter square pressure during this process.
  • The economizer heats this water at the saturation point in ideal condition and sends it to the boiler drum.
  • The water from the boiler drum sends to the circular ring which is situated at the bottom of the boiler. All the water wall tubes are connected to this circular ring.  
  • Now the water flow through the water wall tube of boiler which one end is connected to the circular ring and other end is connected to the boiler drum. The water flow from bottom to up direction.
  • This water converts into steam in water walls and send back to boiler drum. Boiler drum separates steam and water. 
  • Now the steam from the boiler drum sends to the super heater which heat the steam around 550 degree centigrade.
  • This superheated high pressurized steam passes through HP turbine where it expands and rotates the turbine. The pressure and temperature of steam drop down in HP turbine.
  • This steam from the exhaust of HP turbine sends back to re-heater where it heat again and achieve the initial temperature around 550 degree centigrade. One thing note down that the steam get its initial temperature but the pressure of the steam is lower than the initial condition.
  • Now this reheated intermediate pressure steam send to IP turbine where it expand again and drop its pressure and temperature down further. It rotates the IP turbine at the same speed as rotate HP turbine.
  • This steam from the IP turbine sends directly to the LP turbine and allowed to expand there. The steam in LP turbine expands completely and done the maximum work.
  • Now from the LP turbine outlet, steam send to the condenser. Condenser is situated just below the LP exhaust line. For cooling of steam in the condenser, cooling tower supplies cold water in the tubes situated in the condenser.
  • The steam converts into water in the condenser and send to the LP heater. LP heaters extract heat from the exhaust of the LP turbine and use it to heat the feed water.
  • After from LP heaters, the water sends to the deaerator where the dissolve gases of water removed. The water from deaerator sends to the BFP which send it to economizer through HP heater.

This water cycle repeats again and again and rotates the turbine continuously. The turbine further rotates the generator rotor and produces electricity.

Advantages and Disadvantages of Thermal Power Plant:


  • Low setup and maintenance cost.
  • It is not directly related to climate condition like hydro power plant.
  • Large amount of coal available at earth. 
  • Easy maintenance.
  • Less land area required.
  • It can be installed near load center which minimize transmission losses.
  • It can be installed near coal mines which can minimize transportation cost of fuel. 


  • Low cyclic efficiency around 35 to 45 percent.
  • It continuously generates smoke which contributes in increase air pollution.
  • It uses consumable fuel.
  • Operation cost is high compare to hydro and nuclear power plant.
  • It creates large amount of ash per hour so ash handling is quiet difficult. 
  • Sometimes heated water directly drawn into river which can harm life cycle of water living.

This is all about thermal steam power plant. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on social networks. Subscribe our website for more informative articles. 

Saturday, 9 September 2017

Boiling Curve and Types of Boiling

Today we will discuss about boiling, boiling curve and types of boiling. Boiling is a major concern for any thermal industry. It is a phenomenon in which water is converted into steam or we can say it is a phase change process from liquid state to gases state. When liquid is heated to its saturation temperature (a temperature at which the liquid starts to convert into vapor) its vapor pressure becomes higher than the surrounding pressure of atmosphere. Due to this pressure difference the liquid particles start to move into atmosphere. This process is known as boiling.

What is boiling?

Boiling can be easily understood by the following experiment.

Let’s takes water into an open container at room temperature.  The container is open to atmosphere so the pressure exerted by the surrounding to the water is atmospheric pressure. Now put the container on fire which added heat and rises the temperature as well as energy of water. Due to this energy rises vapor pressure of water also increases. After continuous heating we reach a point at which the vapor pressure of water becomes equal to atmospheric pressure. This point is known as boiling point. Further increase in temperature causes to increase in vapor pressure and it becomes more than atmospheric pressure which causes movement of water particle into atmosphere. Further rise in temperature converts whole water into steam. This phenomenon is known as boiling.

The temperature at which the boiling starts is known as saturation temperature at constant pressure. The saturation temperature of water at atmospheric pressure is 100 degree centigrade. If the pressure increases the saturation temperature is also increases.

Boiling Curve and Types of Boiling:

Let’s take a look of the curve given below.

Boiling Curve and Types of Boiling

This curve is known as boiling curve. This curve is divided into four regions according to heat transfer phenomenon. When we continuously supply heat into water the phase change process takes place. This process depends upon the surface temperature. These regions sometimes refer as types of boiling.  

Natural Convection Boiling:

AB is the first most regions in which the heat transfer process takes place by free convection. The water particles associated with the heating surface take heat from it and start moving at the top. Now the other particles occupied blank space and start heated from heating surface. This process continuously run until whole water is converted into steam.

Nucleate Boiling:

The next region BC is known as Nucleate region or Nucleate type of boiling. This is the most desirable part of boiling which is used by many industries. In this region, bubbles formation take place. The water particles associated with the heating surface vaporized and converted into bubbles. These bubbles move at top of the liquid and collapse. This region can be further divided into two regions.

The first one is shown by BB’ in which bubbles formation take place and the bubbles start to move at top side. These bubble passes form water which is below its saturation temperature so the bubbles transfer its heat to surrounded water particle and collapse into water.

The other region is B’C in which the whole water converted at saturation temperature and the bubbles start to pass from surrounded water. They do not transfer its heat into surrounding and they collapse at the top of the liquid and release steam into surrounding. This phenomenon of boiling is known as nucleate boiling. This region provides maximum heat transfer rate.  The top most point at boiling curve in nucleate boiling region is known as critical heat flux point.

Transition Boiling:

The third region is shown by CD which is known as transition region. This region is nothing but the mediator region of nucleate boiling and film boiling. This is very undesirable part of boiling curve due to its poor heat transfer rate. In this region the water particles associated with the heating surface converted into steam and forms a vapor blanket. This blanket has poor heat transfer rate thus other liquid particles find hard to take heat from source. This is the reason behind the low heat transfer rate and the undesirability. The lowest point of transition region is known as Leidenfrost Point.

Film Boiling:

The last but the least part of boiling curve or types of boiling is known as film boiling. This region has huge heat transfer rate. It is shown by DE in boiling curve. This region has highest temperature difference between water and the heat source. When we increase this difference further the heat transfer rate increases continuously. In this region the most of heat is transferred by radiation. When we further increase the temperature of heat source after transition region the density of vapor blanket start decrease and form a radiation heat transfer region between liquid particles and heat source. That’s why this region shows significant increase in heat transfer rate.

These are the most common boiling region of boiling curve or types of boiling. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on social networks. Subscribe our website for more informative articles.

Thursday, 8 June 2017

Full Notes on Constant Mesh Gearbox

Constant mesh gearbox is used for the smooth working of an automobile. They are used to increase the rotating force (Torque); this is accompanied by a reduction in speed. It is a type of manual transmission. The invention of earliest manual gear system can be traced back to the nineteenth century. There are multiple gear ratios present which provides various torque and speed ratio. Along with this, the reverse mechanism is also present. This manual transmissions which are developed recently contain all the gears mesh at any given point of time. 

In technical terms, it can be defined as a gearbox in which all the gears are always in a state of mesh. The gears remain fixed at their original positions. The gears will remain engaged at all times. Learn more about its construction, working, advantages, disadvantages and applications in this article.

Constant Mesh Gearbox:


It is made up of following components:

Full Notes on Constant Mesh Gearbox

1. Counter shaft or Lay Shaft: 
This shaft is in direct contact with the clutch and the main shaft. Keeping in mind according to the gear ratio, the speed of the counter shaft may be less that the speed of the engine. The gear ratio can be defined as the ratio of the teeth of driven gear to the teeth of the driver gear.

2. Main shaft:
This shaft operates the speed of the vehicle. The power is made available to the main shaft through the gears from the counter shaft. This is done in accordance with the gear ratio.

3. Dog clutch:
Dog clutch is special feature of constant mesh gearbox. It is used for the coupling of any two shafts. This is done by interference. Using a dog clutch, various gears can be locked to the output and input shafts.

4. Gears: 
The main work of the gears is the transmission of power between the shafts. If the gear ratio is more than one, the main shaft will work at a speed that is slower than the counter shaft, and vice versa. The arrangement of both reverse, as well as forward gears, is present.


Forward gear selection:
From the input shaft, the power starts flowing and is divided into four parts. Each part goes to one of the output gears, namely first, second, third and fourth. Gear ratios can be obtained for each of them. This can be done by the proper sliding of dog clutch over the teeth of the selected gearwheel. After this the path of the energy flow completes. This happens due to the locking movement of the output shaft.

Reverse gear selection:
The power will flow from the input shaft to the reverse gears. The power is then transmitted from the reverse gear to the reverse idler. The idler wheel will change the direction of the rotation. In the case of forwarding direction gear selection, the output gears will rotate in a direction opposite to the input gears. But in the case of reverse gear selection, the rotation is in the same direction as the input shaft.

The steps are taken to change any gear in the constant mesh gearbox system:

1. The first step when one wants to modify the gear would be the pressing of the clutch. After this comes the neutral state of the vehicle to be achieved. Proper optimization of the engine's speed is required.

2. After the neutral gear, one moves forward to the first gear. The first gear. This process is known as double clutching. Inefficiency in performing the above steps might lead to a harsh and gnashing sound.

Watch the following video for clear understanding of its working.

Advantages and Disadvantages of Constant Mesh Gearbox:

  • The first and foremost benefit of the constant gear mesh is the utilization of helical gears. The double helical gears and the helical gears are extremely beneficial owing to their quieter operating capabilities
  • There are various conditions which might cause harm. In the case of constant mesh gearbox, any harm is suffered entirely by the dog clutch teeth. The teeth belonging to the gear wheels remain intact. This is not the case for sliding mesh gear box.
  • The other gear boxes are noisy and create an unwanted din.
  • It is less efficient than the others due to higher mesh teeth. Skill is required for it.
  • The double clutch mesh is required. This is required to have the spinning movements of the shaft.


Some of the vehicles which use this type of gearboxes are farm trucks, motorcycles, and heavy machinery.

It is very evident that the world today is full of vehicles and relies on this mode of transport. The availability of such mechanisms like constant mesh gearbox which create less noise and are cost effective is a boon for the people.

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