Types of fasteners: Pins and keys - Module 4 Fasteners Lesson 1 Notes | EduRev

: Types of fasteners: Pins and keys - Module 4 Fasteners Lesson 1 Notes | EduRev

 Page 1


 
 
 
 
 
 
 
 
 
Module  
4 
Fasteners 
 
Version 2 ME, IIT Kharagpur 
Page 2


 
 
 
 
 
 
 
 
 
Module  
4 
Fasteners 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
 
 
Lesson  
  1 
Types of fasteners: Pins 
and keys 
 
Version 2 ME, IIT Kharagpur 
Page 3


 
 
 
 
 
 
 
 
 
Module  
4 
Fasteners 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
 
 
Lesson  
  1 
Types of fasteners: Pins 
and keys 
 
Version 2 ME, IIT Kharagpur 
Instructional Objectives 
 
At the end of this lesson, the students should have the knowledge of 
• Fasteners and their types: permanent and detachable fasteners. 
• Different types of pin joints. 
• Different types of keys and their applications. 
  
4.1.1  Introduction: Types of fasteners 
 
A machine or a structure is made of a large number of parts and they need be 
joined suitably for the machine to operate satisfactorily. Parts are joined by 
fasteners and they are conveniently classified as permanent or detachable 
fasteners. They are often sub- divided under the main headings as follows: 
 
Permanent fasteners: Riveted joints 
      Welded joints 
Detachable joints: Threaded fasteners – screws, bolts and nuts, studs. 
Cotter joints  
Knuckle joints 
 
  Keys and Pin joints 
 
Starting with the simple pin and key joints all the main fasteners will be discussed 
here. 
4.1.2  Pin Joints  
These are primarily used to prevent sliding of one part on the other, such as, to 
secure wheels, gears, pulleys, levers etc. on shafts. Pins and keys are primarily 
used to transmit torque and to prevent axial motion. In engineering practice the 
following types of pins are generally used. 
 
Version 2 ME, IIT Kharagpur 
Page 4


 
 
 
 
 
 
 
 
 
Module  
4 
Fasteners 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
 
 
Lesson  
  1 
Types of fasteners: Pins 
and keys 
 
Version 2 ME, IIT Kharagpur 
Instructional Objectives 
 
At the end of this lesson, the students should have the knowledge of 
• Fasteners and their types: permanent and detachable fasteners. 
• Different types of pin joints. 
• Different types of keys and their applications. 
  
4.1.1  Introduction: Types of fasteners 
 
A machine or a structure is made of a large number of parts and they need be 
joined suitably for the machine to operate satisfactorily. Parts are joined by 
fasteners and they are conveniently classified as permanent or detachable 
fasteners. They are often sub- divided under the main headings as follows: 
 
Permanent fasteners: Riveted joints 
      Welded joints 
Detachable joints: Threaded fasteners – screws, bolts and nuts, studs. 
Cotter joints  
Knuckle joints 
 
  Keys and Pin joints 
 
Starting with the simple pin and key joints all the main fasteners will be discussed 
here. 
4.1.2  Pin Joints  
These are primarily used to prevent sliding of one part on the other, such as, to 
secure wheels, gears, pulleys, levers etc. on shafts. Pins and keys are primarily 
used to transmit torque and to prevent axial motion. In engineering practice the 
following types of pins are generally used. 
 
Version 2 ME, IIT Kharagpur 
(a) Round pins (b) Taper pins (c) Dowel pins (d) Split pins 
Round and taper pins are simple cylindrical pins with or without a taper and they 
offer effective means of fastening pulleys, gears or levers to a shaft. It may be 
fitted such that half the pin lies in the hub and the other half in the shaft as shown 
in figure-4.1.2.1 (b). The pin may be driven through the hub and the shaft as in 
figure- 4.1.2.1 (c) or as in figure- 4.1.2.1 (d). These joints give positive grip and 
the pins are subjected to a shear load. For example, for the shaft in the assembly 
shown in figure- 4.1.2.1 (c), the pin is under double shear and we have  
2 1
D
2d . T
42
p ??
t=
??
??
 
where d is the diameter of the pin at hub-shaft interface, t is  the yield strength in 
shear of the pin material and T is the torque transmitted. 
 
D
1
d
1
d
2
 
 
 
 
 
 
 
  
Pin
Hub
Shaft
L
d
1
d
2
(d)
(a)
(c)
(b)
 
   4.1.2.1F- Different types of pin joints 
A taper pin is preferred over the straight cylindrical pins because they can be 
driven easily and it is easy to ream a taper hole. 
 
Dowel pins 
These are used to keep two machine parts in proper alignment. Figure- 4.1.2.2 
demonstrates the use of dowel pins. Small cylindrical pins are normally used for 
this purpose. 
Version 2 ME, IIT Kharagpur 
Page 5


 
 
 
 
 
 
 
 
 
Module  
4 
Fasteners 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
 
 
Lesson  
  1 
Types of fasteners: Pins 
and keys 
 
Version 2 ME, IIT Kharagpur 
Instructional Objectives 
 
At the end of this lesson, the students should have the knowledge of 
• Fasteners and their types: permanent and detachable fasteners. 
• Different types of pin joints. 
• Different types of keys and their applications. 
  
4.1.1  Introduction: Types of fasteners 
 
A machine or a structure is made of a large number of parts and they need be 
joined suitably for the machine to operate satisfactorily. Parts are joined by 
fasteners and they are conveniently classified as permanent or detachable 
fasteners. They are often sub- divided under the main headings as follows: 
 
Permanent fasteners: Riveted joints 
      Welded joints 
Detachable joints: Threaded fasteners – screws, bolts and nuts, studs. 
Cotter joints  
Knuckle joints 
 
  Keys and Pin joints 
 
Starting with the simple pin and key joints all the main fasteners will be discussed 
here. 
4.1.2  Pin Joints  
These are primarily used to prevent sliding of one part on the other, such as, to 
secure wheels, gears, pulleys, levers etc. on shafts. Pins and keys are primarily 
used to transmit torque and to prevent axial motion. In engineering practice the 
following types of pins are generally used. 
 
Version 2 ME, IIT Kharagpur 
(a) Round pins (b) Taper pins (c) Dowel pins (d) Split pins 
Round and taper pins are simple cylindrical pins with or without a taper and they 
offer effective means of fastening pulleys, gears or levers to a shaft. It may be 
fitted such that half the pin lies in the hub and the other half in the shaft as shown 
in figure-4.1.2.1 (b). The pin may be driven through the hub and the shaft as in 
figure- 4.1.2.1 (c) or as in figure- 4.1.2.1 (d). These joints give positive grip and 
the pins are subjected to a shear load. For example, for the shaft in the assembly 
shown in figure- 4.1.2.1 (c), the pin is under double shear and we have  
2 1
D
2d . T
42
p ??
t=
??
??
 
where d is the diameter of the pin at hub-shaft interface, t is  the yield strength in 
shear of the pin material and T is the torque transmitted. 
 
D
1
d
1
d
2
 
 
 
 
 
 
 
  
Pin
Hub
Shaft
L
d
1
d
2
(d)
(a)
(c)
(b)
 
   4.1.2.1F- Different types of pin joints 
A taper pin is preferred over the straight cylindrical pins because they can be 
driven easily and it is easy to ream a taper hole. 
 
Dowel pins 
These are used to keep two machine parts in proper alignment. Figure- 4.1.2.2 
demonstrates the use of dowel pins. Small cylindrical pins are normally used for 
this purpose. 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
 
 
  
   4.1.2.2F- Some uses of Dowel pins (Ref.[6]). 
(a)
(b)
Split pins 
These are sometimes called cotter pins also and they are made of annealed iron 
or brass wire.  They are generally of semi-circular cross section and are used to 
prevent nuts from loosening as shown in figure- 4.1.2.3. These are extensively 
used in automobile industry.  
 
 
Split pin
 
 
 
 
 
 
 
 
 
4.1.2.3F- Typical use of a split pin (Ref.[6]). 
 
4.1.3 Keys 
Steel keys are widely used in securing machine parts such as gears and pulleys. 
There is a large variety of machine keys and they may be classified under four 
broad headings: 
Sunk keys, flat keys, saddle keys and pins or round keys 
Version 2 ME, IIT Kharagpur 
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