The gears are classified as follows:
1: The gears which connect parallel shafts such as spur, Helical and double helical gears.
2: The gears which connect inclined and intersecting shafts such as straight bevels and spiral bevel gears.
3: The gears which connects non-parallel and non-intersection shafts such as spiral gears and worm and worm wheel
TYPES
There are many types of gears some of following are important
1: SPUR GEARS:
2: HELICAL GEAR:
3: DOUBLE HELICAL OR HERRINGBONE GEARS:
4: INTERNAL GEARS:
5: BEVEL GEARS:
6: RACK AND PINION:
7: WORM AND WORM GEAR:
Wednesday, January 12, 2011
SYSTEM OF GEAR TEETH
The following four systems of gear teeth are used to manufacture gears.
1: 14 1/2 degree composite system.
2: 14 1/2 degree full depth involute system.
3: 20 degree full depth involute system.
4: 20 degree stub involute system.
The # 1: system is used for general purpose gears.
It is stronger and has no interchange ability.
The tooth profile of this system has cycloid curve at the top and bottom and involute curve at the middle portion. The teeth are produced by form cutters on milling and by hobs on hobbing machine.
The tooth profile of the 14 1/2 degree full depth involute system was developed for use with gear hobs for spur and helical gears. The tooth profile of 20 degree full depth involute system may be cut by using hobs on hobbing machine.
The increase of pressure angle from 14 1.2 degree to 20 degree cause to make the gear teeth strong.
The gear tooth in service acts as a beam and is wider at the base.
The 20 degree stub involute system has a strong tooth to transmit heavy loads.
1: 14 1/2 degree composite system.
2: 14 1/2 degree full depth involute system.
3: 20 degree full depth involute system.
4: 20 degree stub involute system.
The # 1: system is used for general purpose gears.
It is stronger and has no interchange ability.
The tooth profile of this system has cycloid curve at the top and bottom and involute curve at the middle portion. The teeth are produced by form cutters on milling and by hobs on hobbing machine.
The tooth profile of the 14 1/2 degree full depth involute system was developed for use with gear hobs for spur and helical gears. The tooth profile of 20 degree full depth involute system may be cut by using hobs on hobbing machine.
The increase of pressure angle from 14 1.2 degree to 20 degree cause to make the gear teeth strong.
The gear tooth in service acts as a beam and is wider at the base.
The 20 degree stub involute system has a strong tooth to transmit heavy loads.
Tuesday, January 11, 2011
GEAR METERIAL
The selection of material used to manufacture the gears depends upon the conditions like strength, noise and resistance to wear. The gears are manufactured from metallic as well as from non-metallic material. The metallic materials means steel, cast iron, bronze and brass etc. While non-metallic materials include hard wood, raw-hide, compress paper, synthetic resins and nylon etc.
Metallic gears are used to transmit heavy torque while non-metallic gears are used for low and medium power transmission and specially to reduce noise as in case of plain paper photo copier.
The cast iron is most widely used to manufacture gears due to its easy machining, better resistance to wear and ease of producing complex shapes by casting method. The cast iron cut gears are used where smooth action is not important. The phosphor bronze is widely used foe worm gears to reduce wear of the worm.
Metallic gears are used to transmit heavy torque while non-metallic gears are used for low and medium power transmission and specially to reduce noise as in case of plain paper photo copier.
The cast iron is most widely used to manufacture gears due to its easy machining, better resistance to wear and ease of producing complex shapes by casting method. The cast iron cut gears are used where smooth action is not important. The phosphor bronze is widely used foe worm gears to reduce wear of the worm.
Monday, January 10, 2011
SPUR GEAR
INTRODUCTION
When it is required to transmit power from one shaft to another parallel to each other at long distance, we use wire rope or flat belts.
For moderate distances,
V-belts is used for the said purpose. The shafts situated at minimum distances are provided with gears.
The only requirement for transmit power is the exact central distance between shafts.
They previous methods cannot be used to get exact velocity ratio due to slipping between belts and pulleys, therefore toothed wheel or gears are used.
TERMS OF SPRING
PITCH OF SPRING
The pitch of the spring is the axial distance between adjacent turns in uncompressed state.
SPRING INDEX
It is the ratio of mean diameter of the coil to the diameter of the wire. Mathematically;
Spring index = D/d where D = Mean diameter of coil
d = Diameter of the wire
SPRING RATE
Load required oer unit deflection is called spring rate or stiffness.
FREE LENGTH
It is the length of spring measured parallel to the axis when load is completely removed from it.
The pitch of the spring is the axial distance between adjacent turns in uncompressed state.
SPRING INDEX
It is the ratio of mean diameter of the coil to the diameter of the wire. Mathematically;
Spring index = D/d where D = Mean diameter of coil
d = Diameter of the wire
SPRING RATE
Load required oer unit deflection is called spring rate or stiffness.
FREE LENGTH
It is the length of spring measured parallel to the axis when load is completely removed from it.
SPRING MATER
The material for the spring largely depends upon the sirvice for which they are used.
The springs are mostly made from oil tempered carbon steel wires containing.
Music wire is used for small springs.
Non ferous material like phosphor bronze, monal metal, and brass may be used.
The wire of less than 10mm diameter are usually wound cold to make springs while the largr sizes are wound hot.
The springs are mostly made from oil tempered carbon steel wires containing.
Music wire is used for small springs.
Non ferous material like phosphor bronze, monal metal, and brass may be used.
The wire of less than 10mm diameter are usually wound cold to make springs while the largr sizes are wound hot.
PART 4: TYPES OF SPRING
DISC SPRING
These springs consist of number of conical discs held together against slipping by a cinral bolt or tubing. There spring are used where high spring rate and compact spring units ar required
These springs consist of number of conical discs held together against slipping by a cinral bolt or tubing. There spring are used where high spring rate and compact spring units ar required
PART 3: TYPES OF SPRING
LAMINATED SPRING
A laminated or leaf spring in its simplest form consist of a number of parallel strips of metal having different lengths and same width.
These strips areplaced over each other in laminations.
All plates ar strips are allowed to slide over each other
These springs are widely used in road wehicles, coaches and railway wagons.
These are used to absorb shocks which gives unpleasent feeling to passengers.
The energy ebsorbedby the laminated spingis immidiately released.
A laminated or leaf spring in its simplest form consist of a number of parallel strips of metal having different lengths and same width.
These strips areplaced over each other in laminations.
All plates ar strips are allowed to slide over each other
These springs are widely used in road wehicles, coaches and railway wagons.
These are used to absorb shocks which gives unpleasent feeling to passengers.
The energy ebsorbedby the laminated spingis immidiately released.
PART 2: TYPES OF SPRING
CONICAL SPRING
The conical springs are wound with uniform pitches in the form of conic solid.
These springs are used to face vibration problems such as to support a load that has varying mass
TORSION SPRING
These spring are hilical or spiral in round shape
The torsion spring may be used where applied load tends to wind up the spring such as door hinges, shuttering gaes of shops, main switches of different machines.
The spiral torsion spring is used when the load tends to increas the number of coils.
It is usually made up of flat strup and used in wall clocks, children toys and to lift the drilling machine quill.
The conical springs are wound with uniform pitches in the form of conic solid.
These springs are used to face vibration problems such as to support a load that has varying mass
TORSION SPRING
These spring are hilical or spiral in round shape
The torsion spring may be used where applied load tends to wind up the spring such as door hinges, shuttering gaes of shops, main switches of different machines.
The spiral torsion spring is used when the load tends to increas the number of coils.
It is usually made up of flat strup and used in wall clocks, children toys and to lift the drilling machine quill.
PART 1: TYPES OF SPRING
1: HELICAL SPRING
If a wire is wound on cylindrical workpiece along its length, the spring made by this method is called helical spring.
A helical spring is classified as;
(a) Closely coiled helical spring.
(b) Open coiled helical spring.
A helical spring is said to be closely coiled when spring wire is coiled so close so that there is no gap between two adjacent turns or it can be said that each turn is nearly at right angle to the axis of spring.
The spring wire of closely coiled helical spring is subjected to shear stress.
In a closely coiled helical spring, the helix angle is usually less than ten degree.
In a open coiled helical spring, the spring wire is coiled in such a way that there is a large gap between two adjacent turns.
These types of springs are usually used to withstand compressive loads.
If a wire is wound on cylindrical workpiece along its length, the spring made by this method is called helical spring.
A helical spring is classified as;
(a) Closely coiled helical spring.
(b) Open coiled helical spring.
A helical spring is said to be closely coiled when spring wire is coiled so close so that there is no gap between two adjacent turns or it can be said that each turn is nearly at right angle to the axis of spring.
The spring wire of closely coiled helical spring is subjected to shear stress.
In a closely coiled helical spring, the helix angle is usually less than ten degree.
In a open coiled helical spring, the spring wire is coiled in such a way that there is a large gap between two adjacent turns.
These types of springs are usually used to withstand compressive loads.
TYPES OF SPRING
TYPES
Although there are a large number of springs being used in engineering applications but the following are important to satisfy the subject contents:
1: helical spring
2: Conical spring
3: Torsion spring
4: Laminated
5: Disc spring
To read about types see next post
Although there are a large number of springs being used in engineering applications but the following are important to satisfy the subject contents:
1: helical spring
2: Conical spring
3: Torsion spring
4: Laminated
5: Disc spring
To read about types see next post
Sunday, January 9, 2011
SPRINGS
INTRODUCTION
A spring is an elastic body whose function is to defect under some load.
When the load is removed. the spring recovers its original shape and size.
The springs are commonly used in watches, pressure vessels safety valves, door hinges, two wheel and four wheel motor vehicles and railway wagons.
USES OF SPRINGS
Some important uses of springs are as follows;
1: To absorb energy due to shock or vibration.
2: To apply forces as in brakes, spring loaded valves or plunger of dividing head.
3: To control motion by maintaining contact. between two elements such as cam and follower.
4: To measure forces y linear deflection such as in spring balance.
5: To store energy as in wall clocks and children toys.
A spring is an elastic body whose function is to defect under some load.
When the load is removed. the spring recovers its original shape and size.
The springs are commonly used in watches, pressure vessels safety valves, door hinges, two wheel and four wheel motor vehicles and railway wagons.
USES OF SPRINGS
Some important uses of springs are as follows;
1: To absorb energy due to shock or vibration.
2: To apply forces as in brakes, spring loaded valves or plunger of dividing head.
3: To control motion by maintaining contact. between two elements such as cam and follower.
4: To measure forces y linear deflection such as in spring balance.
5: To store energy as in wall clocks and children toys.
TYPES OF SHAFT COUPLING
TYPES
The shaft couplings are classified as:
1: Rigid Coupling
2: Flexible Coupling
1: RIGID COUPLING
This coupling is used to connect two shaft in perfect alignment. Following types of the rigid coupling are important to grasp the contents of the subject:
(a) Sleeve or muff coupling.
(b) Split muff or compression coupling.
(c) Flange coupling.
2: FLEXIBLE COUPLING
Flexible coupling is used to connect two shafts in lateral or angular alignment. The following types of flexible couplings are important to cover the elementary level of the subject:
(a) Bushed pin type coupling.
(b) Universal coupling.
(c) Old-ham's coupling.
The shaft couplings are classified as:
1: Rigid Coupling
2: Flexible Coupling
1: RIGID COUPLING
This coupling is used to connect two shaft in perfect alignment. Following types of the rigid coupling are important to grasp the contents of the subject:
(a) Sleeve or muff coupling.
(b) Split muff or compression coupling.
(c) Flange coupling.
2: FLEXIBLE COUPLING
Flexible coupling is used to connect two shafts in lateral or angular alignment. The following types of flexible couplings are important to cover the elementary level of the subject:
(a) Bushed pin type coupling.
(b) Universal coupling.
(c) Old-ham's coupling.
USES OF SHAFT COUPLINGS
USES
Shaft couplings are used in mechanical mechanism
1: To provide connection for units that are separately manufactured such as motor and generator.
2: To introduce mechanical flexibility.
3: To reduce transmission of shock loads from one shaft to another.
4: To alter the vibration of rotation shaft.
5: To produce protection against over loads.
REQUIREMENTS OF SHAFT COUPLING
A shaft coupling should be able to fulfill the following requirements:
1:It should be easy to connect or disconnect.
2: It should transmit full power from one shaft to the other.
3: It should hold both of the shafts in desired alignment.
4: It should have no projected parts.
Shaft couplings are used in mechanical mechanism
1: To provide connection for units that are separately manufactured such as motor and generator.
2: To introduce mechanical flexibility.
3: To reduce transmission of shock loads from one shaft to another.
4: To alter the vibration of rotation shaft.
5: To produce protection against over loads.
REQUIREMENTS OF SHAFT COUPLING
A shaft coupling should be able to fulfill the following requirements:
1:It should be easy to connect or disconnect.
2: It should transmit full power from one shaft to the other.
3: It should hold both of the shafts in desired alignment.
4: It should have no projected parts.
SHAFT COUPLINGS
INTRODUCTION
Couplings are used to connect two shafts together so that they may act as single unit.
The power is directly transmitted form one shaft to another.
Couplings provide semi-permanent connection of shafts.
A coupling is termed as a device used to make semi-permanent connection between driver and driven shaft, whereas a clutch permits rapid connection or disconnection at the will of the operator or when ever required.
Couplings are used to connect two shafts together so that they may act as single unit.
The power is directly transmitted form one shaft to another.
Couplings provide semi-permanent connection of shafts.
A coupling is termed as a device used to make semi-permanent connection between driver and driven shaft, whereas a clutch permits rapid connection or disconnection at the will of the operator or when ever required.
SHAFTS
INTRODUCTION
A shaft is a rotating machine element which is used to transmit power for one place to another by means of couplings, pulleys and gears etc.
The shafts are usually of solid cylindrical sections but in some case hollow cylindrical shafts are also used.
The shaft may be classified as;
(a) Transmission shaft.
(b) Machine shaft.
(c) Spindle.
(a) Transmission shaft
These shaft transmits power between the source and power absorbing place for example line shafts and over head shafts.
(b) Machine shaft
A machine shaft is an integral part of the machine itself for example crank shaft.
(c) Spindle
It is short rotation shaft which imparts motion to the cutter or work, for example spindle of drilling machine which imparts motion to the cutting tool called twist drill and spindle of lathe machine which imparts motion to the work through some work holding device.
MATERIAL FOR SHAFTS:-
The material used for ordinary shafts is mild steel. When ever high strength is required, alloy steels such as Nickel, Nickel chromium and chrome vanadium steel is used.
The shafts of larger diameter are forged and turned to size.
Generally the shafts o f moderate diameters are made by hot rolling and finished to size by cold drawing. turning or grinding.
A shaft is a rotating machine element which is used to transmit power for one place to another by means of couplings, pulleys and gears etc.
The shafts are usually of solid cylindrical sections but in some case hollow cylindrical shafts are also used.
The shaft may be classified as;
(a) Transmission shaft.
(b) Machine shaft.
(c) Spindle.
(a) Transmission shaft
These shaft transmits power between the source and power absorbing place for example line shafts and over head shafts.
(b) Machine shaft
A machine shaft is an integral part of the machine itself for example crank shaft.
(c) Spindle
It is short rotation shaft which imparts motion to the cutter or work, for example spindle of drilling machine which imparts motion to the cutting tool called twist drill and spindle of lathe machine which imparts motion to the work through some work holding device.
MATERIAL FOR SHAFTS:-
The material used for ordinary shafts is mild steel. When ever high strength is required, alloy steels such as Nickel, Nickel chromium and chrome vanadium steel is used.
The shafts of larger diameter are forged and turned to size.
Generally the shafts o f moderate diameters are made by hot rolling and finished to size by cold drawing. turning or grinding.
KEYS & COTTERS
INTRODUCTION
A Key is a wedge shaped piece of steel.
The key is used to prevent relative motion between. shaft and the mountings such as pulleys, gears etc.
To accommodate key, a groove called key way is cut.
The half of the key way is cut in the shaft as well as in the hub.
The sizes and shapes of the keys have been standardized and proportioned to the diameter of the shaft.
Although there are a large number of keys used in the engineering field but the following types are important form the subject point of view;
1: Sunk Key:-
2: Saddle key:-
3: Tangent key:-
4: Round key:-
5: Splines:-
A Key is a wedge shaped piece of steel.
The key is used to prevent relative motion between. shaft and the mountings such as pulleys, gears etc.
To accommodate key, a groove called key way is cut.
The half of the key way is cut in the shaft as well as in the hub.
The sizes and shapes of the keys have been standardized and proportioned to the diameter of the shaft.
Although there are a large number of keys used in the engineering field but the following types are important form the subject point of view;
1: Sunk Key:-
(a) Rectangular Key:-
(b) Square key:-
(c) Parallel sunk key:-
(d) Jib head key:-
(e) Feather key:-
(f) Wood ruffs key:-
(a) Flat saddle key:-
(b) Hollow saddle key
(a) Left tangent key:-
(b) Right tangent key:-
4: Round key:-
(a) Round pin:-
(b) Taper pin:-
5: Splines:-
POWER SCREWS
These are used to transmit power in screw operated machines such as lathe machine, shaper, milling machine and screw jacks etc.
Power screws are used to convert rotary motion into linear motion.
A power screw should be made with the material having high resistance to wear and tear.
The power screws should be strong enough to with-stand tensile, shear and compressive loads easily.
The following threads are used for power transmission.
1: Square thread.
2: Acme thread.
3: Buttress thread.
The square thread has maximum efficiency to transmit power in both directions.
This thread is difficult to manufacture. For larger lea and efficient operation multiple threads are used. Acme thread is slightly less efficient as compared to square thread.
This thread is easy to manufacture and it is stronger at root area.
The buttress thread is used to transmit power in single direction only.
This thread is used on the spindles of vices i.e. Wood working vice.
Power screws are used to convert rotary motion into linear motion.
A power screw should be made with the material having high resistance to wear and tear.
The power screws should be strong enough to with-stand tensile, shear and compressive loads easily.
The following threads are used for power transmission.
1: Square thread.
2: Acme thread.
3: Buttress thread.
The square thread has maximum efficiency to transmit power in both directions.
This thread is difficult to manufacture. For larger lea and efficient operation multiple threads are used. Acme thread is slightly less efficient as compared to square thread.
This thread is easy to manufacture and it is stronger at root area.
The buttress thread is used to transmit power in single direction only.
This thread is used on the spindles of vices i.e. Wood working vice.
TYPES OF THREAD
TYPES
various types of threads being used in engineering field are as follows;
1: British Association thread
(B.A. Thread):-
2: V - Thread:-
3: British standard whit-worth
(B.S.W) thread:-
4: Square thread:-
5: Acme thread:-
6: Buttress thread:-
7: Knuckle thread:-
8: American national standard thread:-
9: Metric thread:-
various types of threads being used in engineering field are as follows;
1: British Association thread
(B.A. Thread):-
2: V - Thread:-
3: British standard whit-worth
(B.S.W) thread:-
4: Square thread:-
5: Acme thread:-
6: Buttress thread:-
7: Knuckle thread:-
8: American national standard thread:-
9: Metric thread:-
LEFT HAND & RIGHT HAND THREADS
LEFT HAND & RIGHT HAND THREADS
A right hand thread advances into he same size of threaded hole when turned in clock wise direction.
A left hand thread advances into the same sixe of threaded hole whin turne in anti clock wise direction.
If any thread is not spocified whether. It is right hand or left hand, It is always considered right hand thread.
A lift hand thread is always marked (LH).
The silple convention to indicate a thread by drawing two lines indicating the depth of thread.
A right hand thread advances into he same size of threaded hole when turned in clock wise direction.
A left hand thread advances into the same sixe of threaded hole whin turne in anti clock wise direction.
If any thread is not spocified whether. It is right hand or left hand, It is always considered right hand thread.
A lift hand thread is always marked (LH).
The silple convention to indicate a thread by drawing two lines indicating the depth of thread.
RIGHT HAND GRIP
1.3
PARTS OF SCREW THREAD
A screw threas has the folloeing parts ans shown in fig 1.1
fig. 1.1
1: PITCH
It is the distance between the same points of adjacent threads measured parallel to the axis of the screw.
2: LEAD
It is the distance that a nut will advance on its bolt along the axis of Thread in one turn or revolution.
I single start thread load and pitch are equal.
L=Lead of thread.
P=Pitch of thread.
In single start thread;
L=P
In double start thread;
L=2P
The angle included between the sides of the thread is known as angle of thread.
4: CREST
Crest is the top surface joining the two sides of a thread.
5: ROOT
It is the bottom the crest and the root of thread.
6: FLANK
It is the surface between the crest and the rot of thread.
7: DEPTH OF THREAD
It is defined as the distance measured perpendicular the the axis.
8: MAJOR DIAMETER
It is the largest diameter of the thread.
Major diameter = Minor diameter + 2depth of thread.
9: MINOR DIAMETER
It is the smallest diameter of the screw thread minor
Minor diameter = Major diameter - 2depth of thread.
10: PITCH DIAMETER
It is defined as the diameter of an imaginary cylinder which would pass through the threads at such points that the width of the grooves and the width of threads cut by the surface of cylinder are the same
Pitch diameter = Major diameter - Depth of thread.
A screw threas has the folloeing parts ans shown in fig 1.1
fig. 1.1
1: PITCH
It is the distance between the same points of adjacent threads measured parallel to the axis of the screw.
2: LEAD
It is the distance that a nut will advance on its bolt along the axis of Thread in one turn or revolution.
I single start thread load and pitch are equal.
L=Lead of thread.
P=Pitch of thread.
In single start thread;
L=P
In double start thread;
L=2P
fig.1.2
3: ANGLE OF THREAD
The angle included between the sides of the thread is known as angle of thread.
4: CREST
Crest is the top surface joining the two sides of a thread.
5: ROOT
It is the bottom the crest and the root of thread.
6: FLANK
It is the surface between the crest and the rot of thread.
7: DEPTH OF THREAD
It is defined as the distance measured perpendicular the the axis.
8: MAJOR DIAMETER
It is the largest diameter of the thread.
Major diameter = Minor diameter + 2depth of thread.
9: MINOR DIAMETER
It is the smallest diameter of the screw thread minor
Minor diameter = Major diameter - 2depth of thread.
10: PITCH DIAMETER
It is defined as the diameter of an imaginary cylinder which would pass through the threads at such points that the width of the grooves and the width of threads cut by the surface of cylinder are the same
Pitch diameter = Major diameter - Depth of thread.
Saturday, January 8, 2011
SCREWS
INTRODUCTION
Screw hreads are helical in dorm and helical ridges are formed by cutting or rollig a grooves into the surface of cylindical bar, are called ecternal threads and threads ct in a hole are called internal threads.
The scres are also used for power transmssion such as lead screws of Lathe machine, Milling machine and fly presses etc.
TYPES OF SCREWS
1: Cap screws
2: Machine screws
3: Set screws
Screw hreads are helical in dorm and helical ridges are formed by cutting or rollig a grooves into the surface of cylindical bar, are called ecternal threads and threads ct in a hole are called internal threads.
The scres are also used for power transmssion such as lead screws of Lathe machine, Milling machine and fly presses etc.
TYPES OF SCREWS
1: Cap screws
2: Machine screws
3: Set screws
ADVANTAGES & DISADVANTAGES OF SCREWED JOINTS
ADVANTAGES OF SCREWED JOINTS
The advantages of the screwed joints are as follows:
1: Screwed joints are highly relabel in service.
2: screwed joints are easy to assemble and disassemble.
3: A wide range of screwed joints is available to adopted under various working conditions
4: Screws are relatively cheap.
5: Due to standardization, cheap manufacturing processes can be adopted.
6: Screws can be used to transmit power such as lead screw.
DISADVANTAGES OF SCREWED JOINTS
1: The stress concentration in the threaded portions is variable under variable conditions
2: he strength of the screwed joints is not comparable with welded or riveted joints.
3: Screwed joints become loose due to machine vibrations.
The advantages of the screwed joints are as follows:
1: Screwed joints are highly relabel in service.
2: screwed joints are easy to assemble and disassemble.
3: A wide range of screwed joints is available to adopted under various working conditions
4: Screws are relatively cheap.
5: Due to standardization, cheap manufacturing processes can be adopted.
6: Screws can be used to transmit power such as lead screw.
DISADVANTAGES OF SCREWED JOINTS
1: The stress concentration in the threaded portions is variable under variable conditions
2: he strength of the screwed joints is not comparable with welded or riveted joints.
3: Screwed joints become loose due to machine vibrations.
SCREWED JOINTS
Introduction
There are many kids machine fastening being used for diffeent purposes.
Bolts and screws are used for diffrent purposes.
Bolts and screws are used to clamp or fasten machine parts together in such a manner that they cannnnnn be assembled or disassembled, readily.
A screw joint is mainly composed of two elements i.e. boly and nut.
The screw joints are used to assemble the parts, to hold parts for repair, to hold parts for inpection or hold the parts for manufacturing etc.
There are many kids machine fastening being used for diffeent purposes.
Bolts and screws are used for diffrent purposes.
Bolts and screws are used to clamp or fasten machine parts together in such a manner that they cannnnnn be assembled or disassembled, readily.
A screw joint is mainly composed of two elements i.e. boly and nut.
The screw joints are used to assemble the parts, to hold parts for repair, to hold parts for inpection or hold the parts for manufacturing etc.
DISADVANTAGES OF WELDED JOINTS
DISADVANTAGES OF WELDED JOINTS
1: due to the unevenrate of cooling, additional sress are developed in the partd to be welded.
2: welding requires highly skilled lablur and supervision.
3: There is no provision of expansion and contraction therefore some times the structure cracks.
4: The inspection of weldid joints is ddfficult as compared to riveted joints.
1: due to the unevenrate of cooling, additional sress are developed in the partd to be welded.
2: welding requires highly skilled lablur and supervision.
3: There is no provision of expansion and contraction therefore some times the structure cracks.
4: The inspection of weldid joints is ddfficult as compared to riveted joints.
ADVANTAGES OF WELDED JOINTS
ADVANTAGES OF WELDED JOINT
The welded structures are lighter in weight as compared to riveted structures.
2: The welded joints are reliable and have greater efficiency as compared to riveted joints.
3: The welded structure is smooth in appearance with respect to riveted structure
4: In welded structure, the tension member are not weakened as in case of riveted structures,.
5: Cylindrical shells can easily be welded. It is difficult to rivet them.
6: The process of welding takes time as compared to riveting.
The welded structures are lighter in weight as compared to riveted structures.
2: The welded joints are reliable and have greater efficiency as compared to riveted joints.
3: The welded structure is smooth in appearance with respect to riveted structure
4: In welded structure, the tension member are not weakened as in case of riveted structures,.
5: Cylindrical shells can easily be welded. It is difficult to rivet them.
6: The process of welding takes time as compared to riveting.
Friday, January 7, 2011
WELDED JOINTS
INTRODUCTION
Welded joints are more widely used in fabrication work.
In these days the welded joints are replacing bolted or riveted joints.
The welded joints heave greater efficiency as compared to the riveted joints.
These joints are used to repair different. structures or to unite two parts.
A welded joint is permanent joint.
It is obtained by the fusion of edges of components to be joined with or without the use of filler meter.
The heat required for welding is obtained by fusion of acetylene gas welding and by an electric arc as in arc welding.
Welded joints are more widely used in fabrication work.
In these days the welded joints are replacing bolted or riveted joints.
The welded joints heave greater efficiency as compared to the riveted joints.
These joints are used to repair different. structures or to unite two parts.
A welded joint is permanent joint.
It is obtained by the fusion of edges of components to be joined with or without the use of filler meter.
The heat required for welding is obtained by fusion of acetylene gas welding and by an electric arc as in arc welding.
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