FASTENERS-BOLT-NUT-LOCKING NUT-FITTER ONLINE NOTE

INTRODUCTION OF FASTENERS

i)- All big or small machines are made by joining different parts. 

ii)- There are so many methods to assemble the machines parts with each other these are called fasteners. 

iii)- The process by which these are assembled is called fastening. 

iv)- There are three main methods of fastening: (a) Temporary fastening, (b) Semi-permanent fastening, (c) Permanent fastening

(a) Temporary Fastening : 

i)- This is a type of fastening by which different parts of machine can be opened or re-assembled without any damage. 

ii)- In this neither job nor fastener is damaged like nut and bolt, key, screw and pin etc.

(b) Semi-permanent Fastening: 

i)- In this method there is no risk of damage to job but fastener is damaged. 

ii)- This system is used where there is a chance of opening of the parts due to some reason, For example soldering and riveting etc is Semi-permanent Fastener.

(c) Permanent Fastening: 

i)- This is a such type of fastener which becomes part of a machine or parts after fastening. 

ii)- This system both job and fastener damage on opening. 

iii)- These are example for brazing and welding is a Permanent Fastening.

TEMPORARY FASTENERS

BOLT:- 

i)- It is round piece of rod having head on one edge and thread cutting on the other edge for nut to tight in it. 

ii)- Bolt is normally made to mild steel but for some special works it is also made of brass, copper and other metals. 

iii)- Its size is measured from thread side to its length except head. 

iv)-These are classified as per the shape of their head. 

v)- There are many types of bolt as per the shape of the head. 

(1) Hexagonal Head Bolt: 

i)- This type of bolt is mostly used. 

ii)- For loosening and tightening spanners are used. 

iii)- The upper portion of head is chamfered at 30 angle. 

iv)- Bolt head has a standard size.

a)- If D = Bolt nominal diameter

b)- Chamfer angle= 30°

c)- Thickness of head = 0.7 D to D

d)- Length is measured except head.

(2) Square Head Bolt: 

i)- This bolt has square head. 

ii)- It is used by fastening its head in square or rectangular grooves. 

iii)- It is also used in general works or shaft and bearing.

iv)- Its head's upper edge is chamfered.

v)- When head of square head bolt kept in open then for such works bolt head has square cross-section neck.

a)- Bolt diameter D

b)- Thickness of head-3/4 D

c)- Chamfer radius 7/4 D  

                                                                                               

(3) Cup or Round Head Bolt:-

i)- It has round head

ii)- It is not possible to hold it due to round head.

iii)- It is flat from bellow,the head with snag in some of its part which protect it from moving during tightening of bolt.

iv)- It is mostly used for wood work.

(4) 'T' Head Bolt:-

It is used to tight clamping devices or job in machine table.

It has rectangular head and square neck.

(5) Eye Bolt:-

i)- This bolt has round head.

ii)- It is used to lift heavy machine.

iii)- These are made thick and thin according to weight of machine and have full threading on its length.

(6) Hook Bolt:-

i)- Its head is not fully round but one side has a cut.

ii)- A square neck is made bellow its head which protect it from moving.

It is also used to lift the machine.

(7) Counter Sunk Head Bolt:-

i)- This bolt has a tapper from upper side of head to neck.

ii)- It is used in that places where bolt head should be bellow the flat surface of parts.

iii)- Some bolt head has sung or square.

(8) Taper Head Less Bolt:-

This type of bolt has no head.

This is used for shaft clamping of machine.

NUT:-

i)- Nut is a piece of iron or Non-ferrous metal having internal threading on it.

ii)- Nut can be fitted in bolt or stud to joint more then one parts.

iii)- According to construction there are many types of nut.

1)- Hexagonal Nut:-

i)- It is six side nut hexagonal shape.

ii)- Its edge chamfered at 30 degree angle.

iii)- Normally these are very widely used.

iv)- To tight or loose the nut spanner is used.

v)- Its value is calculated as explained bellow

a)- Diameter of Bolt = D

b)- Distance between one side to another side = W= 3/2 D+1/8

c)- Chamfer radius = 0.13 D

d)- Thickness of Nut = T = D

2)- Square Nut:-

i)- It is square type of nut.

ii)- Its upper portion is chamfered at 30 degree angle.

iii)- Its used for light work because its thickness is less then hexagonal nut.

iv)- Its size is measured like square head bolt.

v)- Its side is gripping better on spanner.

3)- Cap Nut:-

i)- It is also like hexagonal nut the only difference is that it has cap on it.

ii)- Due to cap bolt is covered with it and is protected from rust.

iii)- There is no leakage on pressure place.

4)- Capstan Nut:-

i)- It is round shape nut with 3/16 inch diameter drill hole on outer periphery or face.

ii)- It is opened or tightened with the help of tomy bar or prin face spanner.

5)- Knurling Nut:-

i)- It is also round in shape with knurling on its periphery .

ii)- These are opened or tightened with hand. 

iii)- These are used for frequently opening or tightening in measuring instruments.

6)- wing Nut: 

i)- It is also called fly nut. 

ii)- It has two wings on its outer periphery so due to this, it is called fly nut. 

iii)- It is easy to open or tight the nut with the help of their wings. 

iv)- It is used in that places where frequent opening or tightening is required like gripping of hexablade in hexa frame etc.

LOCKING SYSTEM

The places having more vibrations or strikes there is a chance of opening of nut, to remove this defect the following systems are used:
(1) Lock Nut: 

i)- In this system before tightening the standard nut, another nut is tightened in it which is thin from normal nut.

ii)- Its thickness is normally from 2/3 D or 3/4 D and both sides have chamfer at 30° angle. 

iii)- This nut protects the standard nut from loosening so it is also called chuck nut.

2)- Castle Nut.

lt is also Like a hexagonal nut but only difference is that it has collar on its head with grooves cutting.

The bolt used for this nut has a hole. 

After tightening the nut a split pin is fixed in groove and hole and then this pin ends

are spread-ed so that there is not any chance of loosing nut.

3)- Slotted Nut:-

i)- It is like a castle nut but only difference is that there is no collar in it. 

ii)- It is weak then other types of nuts.

iii)- The nut upper part as a slot on opposite sides and hole is made in bolt. 

iv)- After tightening the hub slot should be in parallel to hole then split pin is fixed in it.

 v)- Its tail ends spread towards left and right.

4)- Split Pin Nut : 

i)- This nut is like a normal nut. 

ii)- After tightening the nut on a bolt a hole of 3/16 D is made in between head of nut and bolt and split pin is fixed in it. 

iii)- Then split pin tail ends are bent towards letft and right so that nut should not open.