Solid fuels

What are solid fuels?

Solid fuel is the various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion.

The solid fuels find little practical application at present because of the problems in handling the fuel as well as in disposing of, the solid residue or ash after combustion. 

Solid fuels compared to gaseous and liquid fuels, solid fuels are quite difficult to handle and storage and feeding are quite cumbersome.

Solid fuels are categories by following below :

• Biomass ( 5 C and 37 P )
• Charcoal (27 P )
• Coal (13 C and 64 P )
• Oil shale ( 7 C and 12 P )
• Peat ( 2 C and 4 P )
• Wood fuel ( 1 C and 9 P ) 

Now we can see all of the above in details :

Wood fuel :

Content of wood :

• Cellulose 
• Lignin 
• Resins 
• Inorganic material 
• Water ( 25 - 60 % )

Advantages of wood :

• Burns readily
• Soot and ash produced is small
• Ash is reused 
• Easily available 
• Suitable calorific value for domestic use 

Disadvantages of wood :

• A high percentage of water decreases the calorific value 

Peat :

Content of peat :

• Volatile matter ( 10.4 % )
• Fixed carbon ( 4.6 % )
• Moisture ( 85 % )

Advantages of peat :

• Used as fertilizer
• As for packing material 
• As boiler fuel in the form of briquettes 

Disadvantages of peat :

• High water content 
• Burns slowly 
• Low calorific value 
• Not economical 

Coal :

Content of coal :

• Highly complex organic matter 
• Varying quantity of water 
• Nitrogen ( 0.75 % to 1.75 % )
• Sulpher

There are different grades of coal :

• Anthracite ( 86-88 % )
• Bituminous ( 78-66 % )
• Sub-bituminous coal or black lignite 
• Pulverised coal  

Biomass :

Content of biomass :

• Lignin ( Phenolics 26 % )
• Cellulose ( Glucose 44 % )
• Hemicellulose ( Xylose 30 % )

Charcoal :

Content of charcoal :

• Fixed carbon 
• Hydrogen 
• Oxygen 
• Nitrogen
• Sulpher 
• Moisture 
• Ash 

Petrol Vs LPG

LPG characteristics vs petrol characteristics

Petrol :

• Fuel consumption in petrol engine is less when compared to LPG.
• Petrol has odour.
• Octane rating of petrol of 81.
• Petrol engine is not as smooth as LPG engine.
• In order to increase octane number petrol required lead additives.
• Carburetor supplies the mixture of petrol and air in the proper ratio to the engine cylinders for combustion.

LPG :

• Fuel consumption in LPG engine is 10 % increase as compared with the petrol.
• LPG is odourless.
• Octane rating of LPG is 110.
• Due to higher octane rating, combustion of LPG is smoother and knocking is eliminated and the engine runs smoothly.
• LPG is lead-free with high octane number.
• The vaporizer function as the carburetor when the engine runs on LPG. It is a control device that reduces LPG pressure, vaporizes it and supplies to the engine with a regular flow of gas as per the engine requirement.

If you use petrol or LPG as a fuel in car then they differ by following category :

• LPG costs about 40% less than petrol and diesel, in part because of a lower fuel duty.
• LPG is a cleaner burning fuel compared to the above two, but releases even lesser heat than petrol.
• Engine life can be improved due to LPG being a cleaner burning fuel.
• Maintenance is more in LPG used car as compared with petrol.
• LPG vehicle owners pay less road tax than petrol vehicle. 

Future scenario for LPG vehicles

LPG full form is Liquefied Petroleum Gas is Cost-saving, larger life of the engine, and less emission will attract the public for making use of LPG run vehicles. The future of LPG vehicles is bright, provided the following improvements in the system are made.

• At present, in many countries, LPG cylinders are used n the vehicles. The weight of the cylinders is an advantage. Some amount of power is wasted in carrying these cylinders along with the automobile vehicles. However, in developing countries, most LPG cars use LPG tanks. The tank is usually the same size as the spare wheel and fits snugly into space for the spare wheel. 
• Efforts must be made to have more LPG filling stations at convenient locations so that LPG tanks can be filled up easily.
• Safety devices are to be introduced to prevent an accident due to the explosion of gas cylinders or leakage in the gas pipes.

Advantages of using hydrogen as a fuel

Due to low molecular mass and high hydrogen combustion temperature, hydrogen is the most efficient chemical rocket fuel, but the main drawback is extremely low density, which means you need very large tanks. Hydrogen works superbly for fuel cells and has no carbon to burn things up cleanly, producing the most energy of any chemical fuel per unit mass. Let us have a deep insight into the advantages of hydrogen using as a fuel in this article. 

  

Advantages of hydrogen as a fuel : 

• Low emission. The exhaust does not contain CO or HC because the fuel does not contain carbon. H2O and N2 and NOx would be the most exhaust.
• Fuel availability. There is a number of different ways to produce hydrogen including electrolysis of water.
• Fuel leakage to the environment is not a pollutant.
• High energy content per volume when stored as a liquid so the fuel tank is very large. 
• Unlike fossil fuel and non-renewable sources, there is no concern about running out of hydrogen at any time.
• Hydrogen is a completely non-toxic, clean and powerful source of energy. 
• In fact, it is also used as fuel in rockets, it is more powerful.
• Compared to gas and diesel, hydrogen can produce more energy per pound of fuel, making it more fuel-efficient. Cars powered by hydrogen fuel cells can operate more miles than cars powered by solar or gas or any other fuel-powered vehicle.
• If we used hydrogen as a fuel, maintenance is affordable.
• Its supply in the atmosphere is abundant.
• Hydrogen fuel does not degrade.

Disadvantages of using hydrogen as a fuel

Hydrogen is another alternate fuel tried for IC engines. Investigations were carried out extensively in many countries. The most attractive features of hydrogen as an IC engine fuel are that it can be produced from a potentially available raw material, water and the main product of its combustion again is water.

Disadvantages of using hydrogen as a fuel :

• The requirement of heavy, bulky fuel storage both in the vehicle and at the service stations.
• Hydrogen can be stored either as a cryogenic liquid or as a compressed gas. If stored as a liquid, it would have to be kept under pressure at a very low temperature requiring a thermally super-insulated fuel tank.
• Storing in a gas phase would require a high-pressure vessel with limited capacity.
• Hydrogen is difficult to refuel.
• Possibility of detonation.
• Poor engine volumetric efficiency. 
• Fuel cost would be high at present-day technology because costly to produce.
• Also the problem of availability of hydrogen.
• Hydrogen fuel ignites very easily and therefore the design of fuel intake was done with at most care.
• It may not be toxic but it is flammable for sure. This would add unnecessarily and new risk into society.
• While hydrogen is an alternative fuel, a disadvantage is that it still has a dependency on coal, oil, and natural gas.

The automobile company Mazda has adapted a rotary Wankel engine to run on hydrogen fuel. this car uses a metal hybrid fuel storage system.

Comparison of air standard and actual cycles

The actual cycles for internal combustion engines differ from air-standard cycles in many respects. 

The differences are following below :

• The change in the chemical composition of the working substance.
• The variation of specific heat with temperature.
• The change in composition, temperature and the actual amount of fresh charge is because of the residual gases.
• The working substance is a mixture of air and fuel vapor or finely atomized liquid fuel in the air combined with the products of combustion left from the previous cycle.
• Progressive combustion rather than instantaneous combustion.
• The heat transfer to and from the working medium.
• Gas leakage, fluid friction etc.
• The substantial exhaust blows down loss.

Explore more information:

1. Comparison of Otto Diesel and Dual cycles 

Actual cycles and their analysis

The actual cycle for IC engines differs from the fuel-air cycles and air-standard cycles in many respects. The actual cycle efficiency is much lower than the air-standard efficiency due to various losses occurring in the actual engine operation.

The major losses are due to :

• Progressive combustion 
• Variation of specific heats with temperature
• Dissociation of the combustion products
• Incomplete combustion of fuel
• Heat transfer into the walls of the combustion chamber
• Blowdown at the end of the exhaust process
• Gas exchange process

These all losses are made from previous experience and some simple tests on the engines and these estimates can be used in evaluating the performance of an engine.

Comparison of air standard cycle and fuel air cycles

In this article reasons for the difference between air-standard cycles and fuel-air cycles is discussed. 

The magnitude of difference between the two cycles can be attributed to the following factors :

• The character of the cycle ( Due to assumptions ) 
• Equivalence ratio ( Actual F/A / Stoichiometric F/A )
• Chemical composition of the fuel

Air standard cycles differ in many aspects following below :

1. The variation of specific heat with temperature
2. The change in pressure temperature
3. Change of specific heat with temperature
4. The working substance is a mixture of air and fuel vapour

Comparison of otto diesel and dual cycles

The operating cycle of an internal combustion engine can be broken down into a sequence of separate processes such as intake, compression, combustion, expansion, and exhaust. The accurate analysis of the internal combustion engine process is very complicated but in this article, we will discuss the comparison between Otto, diesel, and dual cycles.

First, you should know the main factors which are used as the basis for comparison of the cycles :

• Compression ratio
• Peak pressure
• Heat addition
• Heat rejection 
• Network

In order to compare the performance of these cycles some of the variables which we will see above some of the variable factors must be fixed. This analysis will show which cycle is more efficient for a given set of operating conditions.

Now we do it one by one all variables are fixed and then make a comparison.

• Same compression ratio and Heat addition :

Otto cycle has the highest work output and efficiency.

Diesel cycle has the least efficiency.

The dual cycle has the efficiency between the Otto and diesel cycle.

ŋ_Otto > ŋ_Dual > ŋ_Diesel 

• Same compression ratio and Hear rejection :

Otto cycle has the highest work output and efficiency.

The diesel cycle has the least efficiency.

The dual cycle has the efficiency between the Otto and diesel cycle.

ŋ_Otto > ŋ_Dual > ŋ_Diesel 

Same as the same compression ratio and hear addition.

• Same Peak pressure, Peak temperature and Heat Rejection :

Also for the same peak pressure, peak temperature and heat Rejection same as above two.

ŋ_Otto > ŋ_Dual > ŋ_Diesel 

• Same Maximum Pressure and Hear Input and Output :

Also for that case same as above all. because now we all know Otto cycle efficiency is always the highest.

ŋ_Otto > ŋ_Dual > ŋ_Diesel

Explore more information:

1. Comparison of air standard cycle and fuel-air cycles
2. Actual cycles and their analysis 
3. Comparison of air standard and actual cycles

Cam terminology

CAM NOMENCLATURE :

Definitions of terms that used in cam profile nomenclature :

• Base circle :

It is the smallest circle drawn a tangent to the cam profile from the centre.

• Tracepoint :

It is a reference point on the follower to trace the cam profile such as the knife-edge of a knife-edge follower and centre of the roller follower.

• Pitch curve :

It is the curve drawn by the tracepoint assuming that the cam is fixed and the tracepoint of the follower rotates around the cam.

• Pressure angle :

It is the angle between the normal to the pitch curve at a point and the direction of the follower motion.

Pressure angle representing the steepness of the cam profile.

• Pitch point :

It is the point on the pitch curve at which the pressure angle is maximum.

• Pitch circle :

It is the circle passing through the pitch point and concentric with the base circle.

• Prime circle :

The smallest circle drawn a tangent to the pitch curve is known as the prime circle.

Displacement diagram :

As a cam rotates about the axis, it imparts a specific motion to the follower which is repeated with each revolution of the cam. It is enough to know the motion of follower for only one revolution.

The motion of the cam can be represented on a graph the x-axis represents the can rotation and the y-axis represents the displacement of the follower. Now we discuss the follower displacement diagram and its terms :

• The angle of ascent :

It is the angle through which the cam turns during the timing of the follower rising. 

In the above figure angle of ascent represent by Ɵ_ri.

• The angle of dwell :

It is the angle through which the cam turns at the same time follower remains stationary at the highest or the lowest position.

In figure angle of dwell represent for the highest position by Ɵ_d1.

• The angle of descent :

It is the angle through which the cam turns during the timing when the follower returns to its initial position.

In figure angle of descent represent by Ɵ_re.

• Angle of action :

It is the angle through which the cam turns during the time between the beginning of rise and the end of the return of the follower. In fact angle of action is the total angle moved by the cam.

In figure angle of action represent by Ɵ.

For variation of cam types and different types of followers motions there are also different different displacement diagram are made. 

Types of followers

Cam followers are different types they are classified according to :

1. Shape
2. Types of follower motion
3. Location of the line of movement

According to shape :

1. Knife-edge follower
2. Roller follower
3. Mushroom follower 

Let we check it out above follower in details :

• Knife-edge follower :

In knife-edge follower, the connecting end of the follower has a sharp knife-edge so that its called knife-edge follower.

This type of follower is quite simple in construction.

It produces great wear of the surface at the point of contact and considerable thrust exist so its use is limited.

• Roller follower :

In roller follower, the connecting end of the follower is a roller so that is called roller follower.

Wear rate is greatly reduced because of rolling motion between contacting surfaces of the cam and follower.

At low speed, the follower has a pure rolling action but at high speeds, some sliding also occurs.

Roller followers are commonly used where more space is available in the large stationary gas or oil engines and aircraft engines.

In case of a steep rise, a roller follower jams the cam and therefore it is not preferred.

• Mushroom follower :

A mushroom follower is also two types :

1. Flat-faced follower
2. Spherical follower

• Flat-faced follower :

In flat-faced follower connecting end of the follower is perfectly flat-faced so that is called flat-faced follower.

The thrust at the bearing exerted is less as compared to another follower.

In this follower, high surface stresses and wear are quite high due to deflection and misalignment.

This types of follower are mostly used in an automobile.

• Spherical follower :

In spherical follower connecting end of the follower is spherical in shape so its called spherical follower.

In flat-faced follower, high surface stress is produced to minimize these stress the follower is machined to spherical shape.

According to follower movement :

1. Reciprocating follower 
2. Oscillating follower 

• Reciprocating follower :

In this type, the cam rotates and the follower reciprocates or translates in the guides of the cam.

This is also called translating follower.

• Oscillating follower :

In this type, cam makes the rotary motion and follower is pivoted at the suitable point on the frame and oscillating as the cam makes a rotary motion.

According to the location of the line of movement :

• Radial follower :

In this type of follower, the line of movement of the follower passes through the centre of rotation of the cam. 

• Offset follower :

In this type of follower, the line of movement of the roller follower is offset from the centre of rotation of the cam.

You may also check different types of the cam.

Types of cam

Cams are classified according to the following terms :

• Shape
• Follower movement
• Manner of the constraint of the follower 

According to shape :

1. Wedge and flat cams
2. Radial or Disc cams
3. Spiral cams
4. Cylindrical cams
5. Conjugate cams
6. Globoid cams
7. Spherical cams

Now explain the above types of cams in details : 

• Wedge and flat cams :

A wedge cam has a wedge W has a translational motion.

The follower F can either translate or oscillate.

In that type of cam, spring is usually, used to maintain the contact between the cam and the follower.

The cam is stationary and the follower constraint or guide G causes the relative motion of the cam and the follower.

• Radial or Disc cams :

  

A cam in which the follower moves radially from the centre of rotation of the cam is known as a radial cam.

Radial cams are very popular due to their simplicity and compactness.

• Spiral cams :

A spiral cam is a face cam in which a groove is cut in the form of a spiral. The spiral groove consists of teeth which mesh with a pin gear follower. 

The use of such cam is limited as the cam has to reverse the direction to reset the position of the follower. It is mainly used in computers.

• Cylindrical cams :

In a cylindrical cam, a cylinder which has a circumferential contour cut in the surface rotates about its axis. For this cam follower motion can be two types :

• A groove is cut on the surface of the cam and a roller follower has a constrained oscillating motion.
• An end cam in which the end of the cylinder is the working surface. 

Cylindrical cams are also known as barrel or drum cams.

• Conjugate cams :

A conjugate cam is a double-disc cam, the two discs being keyed together and are in constant touch with the two rollers of a follower. 

Thus, the follower has a positive constraint. 

Such cam is preferred when the requirements are low wear, low noise, better control of the follower, high speed and high dynamic loads.

• Globoid cams :

A globoid cam can have two types of surfaces, convex or concave. 

A circumferential contour is cut on the surface of rotation of the cam to import the motion to the follower which has an oscillatory motion.

Such types of the cam are used in limited to moderate speeds and where the angle of oscillation of the follower is large.

• Spherical cams :

In spherical cam, the follower oscillates about the axis perpendicular to the axis of rotation of the cam.

This type of cam is in the form of a spherical surface.

According to follower movement :

• Rise-Return-Rise ( R-R-R)
• Dwell-Rise-Return-Dwell ( D-R-R-D )
• Dwell-Rise-Dwell-Return-Dwell ( D-R-D-R-D )

The motion of the followers is distinguished from each other by the dwells they have.

Now the question arises in your mind is what is dwell?

A dwell is zero displacements or the absence of motion of the follower during the motion of cam.

Now explain the above types of cams in details : 

• Rise-Return-Rise ( R-R-R ) :

In this type of cam, there is an alternate rise and return of the follower with no periods of dwells.

In this type of cam follower has a linear or an angular displacement.

• Dwell-Rise-Return-Dwell ( D-R-R-D ) :

In this type of cam there is rise and return of the follower after a dwell.

This type of cam are more frequently used than the R-R-R cam types.

• Dwell-Rise-Dwell-Return-Dwell ( D-R-D-R-D ) :

In this type of cam dwelling of the cam is followed by rise and return.

This type of cam is most widely used cam types.

According to manner of constraint of the follower :

1. Pre-loaded Spring Cam
2. Positive-drive Cam
3. Gravity Cam

Introduction of cam and Follower

In this article, we have to see some basic knowledge about the cam and follower and about cam mechanism. Let we know first what is cam?

A cam is a mechanical member used to impact desired motion to a follower by direct contact.   
                                                                   OR

Cam is the part of a machine in sliding or rolling contact with a rotating cam and given motion by it.

The cam may be rotating or reciprocating whereas the follower may be rotating, reciprocating or oscillating. Now the question may arise that what is a follower?

Cam drives the mating element in mechanical linkage of motion is called FOLLOWER.

There are many different types of the cam are widely used in automobile, automatic machines, internal combustion engine, machine tools, printing control mechanisms etc.

Cams are manufactured by die-casting, milling or by punch-press.

A cam and the follower combination belong to the category of a higher pair. 
In that mechanism :

• A driver member is known as the cam.
• A driven member is known as a follower.
• A frame that can support the cam and guides the follower.

LPG autoignition temperature

What is the autoignition temperature of LPG?

Answer:

• Autoignition temperature of LPG Propane is 470 ⁰C or 878 ⁰F
• Autoignition temperature of LPG Butane is 405 ⁰C or 761 ⁰F

The autoignition temperature decreases as the pressure or oxygen concentration increases.

LPG flame temperature

What is the flame temperature of LPG?

Answer :

• LPG flame temperature is 1980 ⁰C

When LPG is burned properly, the flame colour is blue but sometimes the colour is yellow or red it indicates incomplete combustion.

That property is a consideration while LPG Liquefied petroleum gas is used in mainly automobile vehicle as a fuel or as rural heating. 

Some important facts about LPG

LPG important facts: 

1. LPG full form is Liquefied Petroleum Gas or Liquid Petroleum Gas.
2. LPG is a group of flammable hydrocarbon gases that are liquefied through the use of pressure and commonly used as fuel mostly in an automobile.
3. LPG comes from natural gas processing and while refining petroleum.
4. Propane, butane and isobutane or a mixture of all of this gas es all are fall under LPG gas label.
5. LPG is used for heating, cooking, hot water and vehicles and also used in refrigeration as refrigerant, aerosol propellants and petrochemical feedstock.
6. LPG is mainly stored as a liquid in steel vessels ranging from small gas bottles to the large gas cylinders and storage tank.
7. Sometimes LPG is also called as WET GAS because of its liquidity.
8. It also called NHL means natural gas-liquid.
9. LPG gases are compressed into a liquid at relatively low pressure.
10. Propane does not occur alone naturally.
11. Commercially available LPG is mostly derived mainly from fossil fuels.
12. Real LPG Explosions are Really Rare.
13. LPG is NOT Coal Seam Gas (CSG).
14. LPG is a Renewable Energy Source.

What does LPG stands for?

The meaning of LPG is either liquefied petroleum gas or liquid petroleum gas.

LPG stands by many names and this can something be confusing.

LPG also called sometimes LPG gas, Propane, LP Gas, BBQ Gas, Autogas or Camping Gas.

LPG is a mixture of hydrocarbon and flammable mixture.

LPG is refined petroleum gas used as a green replacement fuel in the converted vehicle because the emission is less in LPG engine as compared with petrol and diesel used as fuel.

LPG used as fuel in heating operation, automobile, rural heating and as a refrigerant in refrigeration.

Milling machine operation

The different operations performed in a milling machine are following below.

1. Plain Milling 
2. Face Milling 
3. Side Milling 
4. Straddle Milling 
5. Angular Milling 
6. Gang Milling 
7. Form Milling 
8. Profile Milling 
9. End Milling 
10. Saw Milling 
11. Milling keyways, Grooves, and slots
12. Gear Cutting 
13. Helical Milling 
14. Cam Milling 
15. Thread Milling 

• Plain milling:

It is the operation of production of a plain, flat or horizontal surface parallel to the axis of rotation of a plain milling cutter.

The operation is also called slab milling.

To perform this operation, the work and the cutter are mounted properly on the machine. The depth of cut is adjusted by rotating the vertical feed screw of the table and the machine is started after selecting the proper speed and feed. 

• Face milling:

This operation is performed by a face milling cutter rotated about an axis perpendicular to the work surface. The operation is carried in a plain milling machine and the cutter is mounted on a stub arbour to produce a flat surface. Hence the face milling operation is done.

• Side milling:

It is the operation of production of a flat vertical surface on the side of a workpiece by using a side milling cutter. 

• Straddle milling:

The straddle is the operation of production of flat vertical surfaces on both sides of the workpiece by using two side milling cutters mounted on the same arbour. This operation is very commonly used to produce square or hexagonal surfaces. 

• Angular milling:

The angular milling is the operation of the production of an angular surface on a workpiece other than at right angles to the axis of the milling machine spindle. The angular groove may be single or double angle but may be of varying included angle according to the type and shape of the angular cutter used.

• Gang milling:

It is the operation of machining many surfaces of a workpiece simultaneously by feeding the table against a number of cutters having same or different diameters mounted on the arbour of the machine.

• Form milling:

It is the operation of producing irregular contours by using form cutter. The irregular contour may be convex, concave or any other shape. After machining, the formed surface is checked by a template gauge. The cutting speed for form milling is 20% to 30% less than that of the plain milling.

• Profile milling :

It is the operation of reproduction of an outline of a template or complex shape of a master die on a workpiece. An end mill is one of the most widely used milling cutters in profile milling work.

• End milling:

It is the operation of production of a flat surface which may be vertical, horizontal or at an angle in reference to the table surface. An end mill cutter is used for this operation. The end milling cutters are also used for the production of slots, grooves or keyways.

The vertical milling machine is most suitable for end milling operation.

• Saw Milling:

It is the operation of the production of narrow slots or grooves on a workpiece by using a sawmilling cutter. 

It can be also be performed for complete parting-off operation.

• Milling keyways, grooves, and slots:

It is the operation of production of keyways, grooves and slots of varying shapes and sizes can be performed in a milling machine by using a plain milling cutter, a plain slitting saw, an end mill or by a side milling cutter.

The open slots can be cut by a plain milling cutter or by a side milling cutter.

The closed slots can be cut by using end mills.

Dovetail slots or T-slots is manufactured by using a special type of cutters.

A woodruff key is produced by using a woodruff key slot cutter.

Standard keyways are cut on shafts by using a side milling cutter or end mills.

The cutter is exactly at the centre line of the workpiece and then the cut is taken.

• Gear cutting:

It is the operation performed in a milling machine by using a form-relieved cutter. The cutter may be a cylindrical type or end mill type. The cutter profile corresponds exactly with the tooth space of the gear. 

• Helical milling:

It is the operation of the production of helical flutes or grooves around the periphery of a cylindrical or conical workpiece.

It is performed by swivelling the table to the required helix angle and then by rotating and feeding the work against the rotary cutting edges of a milling cutter.

• Cam milling:

It is the operation of the production of the cam in a milling machine by the use of a universal dividing head and a vertical milling attachment. The cam blank is secured at the end of the dividing head spindle and an end mill is held in the vertical milling attachment. The axis of the cam blank and the end mill spindle should always remain parallel to each other when setting for cam milling.

• Thread milling:

It is the operation of the production of threads by using a single or multiple thread milling cutter. The operation is performed in special thread milling machines to produce accurate threads in small or large quantities.

This operation required three driving motions in the machine.

• For the cutter
• For the work 
• For the longitudinal movement of the cutter

Read related posts:

1. Milling machine introduction
2. Difference between turning and milling
3. Working principle of milling machine
4. Milling machine safety precautions
5. Milling machine parts
6. Lubrication used in milling machine
7. Types of milling cutter
8. Uses of milling machine
9. What is a milling machine?
10. Milling machine uses