FASTENERS ,LOCKING DEVICES NUTS & BOLTS

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 that places where frequent opening or tighting is required like gripping of wing nut

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 

A thin nut with both faces machined is placed below a nut in the assembly. Both nuts are tightened over the bolt one after the other. Then using two spanners pressure is exerted on both nuts by turning in opposite directions. Both nuts are held together by friction.

- 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.