I have
seen the importance of Coupling and Keys in my industrial life and i am
compelled to write this blog about coupling and keys so that we may share
information about this very precious subject i.e. Coupling and Keys
Let us
see what we want to understand about the coupling and keyÂ
1.
Various types of couplingsÂ
2.
Advantage and disadvantage of various couplingsÂ
3.
Various types of keys and their standard specificationsÂ
4.
Understanding the concept of splines and determine suitable load
5.
Universal joints and their application areas
6.
Shaft attachment mechanisms e.g. Clamps, setscrews and cross pins
First I
would like to focus on key, so let’s go ahead towards the basic concept of
keyÂ
This blog
is based on coupling and keys for shaft and we will focus the
various types of keys here as well as design and selection process that we
must adopted.
KeysÂ
Keys
are normally used for connecting two member mechanically, let us consider gear
coupling and shaft , in this case coupling hub and shaft will be mechanically
connected by means of key. i have seen various types of keys but commonly flat
keys are used inÂ
Flat
KeysÂ
Normally
we use flat key in number of applications, let us understand what is flat key. 
Standard dimensions of
square and flat keys
Shaft diameter
(inch)
|
Square key size
(inch) , h or w
|
Flat key size
(inch) , w*h
|
½* to 9/15
|
1/8
|
1/8 x 3/32
|
5/8 to 7/8
|
3/16
|
3/16x 1/8
|
15/16 to 1*1/4
|
1/4
|
1/4 x 3/15
|
1*5/16 to 1*3/8
|
5/16
|
5/16x1/4
|
1*7/16 to 1*3/4
|
3/8
|
3/8 x1/4
|
1*13/16 to 2*1/4
|
1/2
|
1/2 x3/8
|
2*5/46 to 2*3/4
|
5/8
|
5/8Â Â x 7/16
|
2*7/8 to 3*1/4
|
3/4
|
3/4 x 1/2
|
3*3/8 to 3*3/4
|
7/8
|
7/8 x 5/8
|
3*7/8 to 4*1/2
|
1
|
1 x 3/4
|
4*3/4 to 5*1/2
|
1*1/4
|
1-1/4 x 7/8
|
5*3/4 to 6
|
1*1/2
|
1*1/2 x 1
|
Various types of key
Square
and rectangular parallel key
This
type of key is highly recommended these days for various applications. We will
come to know about the cross section of key and then we can decide whether key
is square or rectangular. Selection of size of key depends on the diameter of
shaft and we have already discussed some standard size of key for various size
of shaft in above table.
Tapered
key
Such
type of keys will have varying rectangular cross-section.
The fundamental idea of adopting taper keys is basically for the
easiness of assembly as well as for removal of the key. 
Gib
Head Key
Such type
of keys are very similar with tapered key but there will be one
difference , in case of gib head key there will be a
head that will be provided at bigger end side of key and
this type of keys are used where we need frequent removal of keys with easiness.
Woodruff
keys
Such
type of key is called as woodruff because of the process of manufacturing of
key and there will be a semi-circular key seat over the surface of shaft and it
will hold the key. The key will be in the circular section shape. But we must
understand that such type of key will have a lesser shear strength as compared
to square or rectangular key.
Circular
KeysÂ
such
type of keys are in circular shape and in this case there will be semi circular
hole in shaft and hub for fixing the circular keys , circular keys are also
known as Pin keys.
Key design
Couplings
A
coupling is used for connecting one shaft end with another shaft
end for transmitting the power from one shaft to another shaft.
Coupling ClassificationsÂ
There are mainly two types of couplings in generalÂ
1. Rigid coupling - Such type of couplings are used for aligned shaftÂ
2. Flexible coupling - Such type of couplings are used for non aligned shaftÂ
Rigid coupling
Coupling ClassificationsÂ
There are mainly two types of couplings in generalÂ
1. Rigid coupling - Such type of couplings are used for aligned shaftÂ
2. Flexible coupling - Such type of couplings are used for non aligned shaftÂ
Rigid coupling
There
will not be any allowable misalignment between both connecting shafts and
members in case of rigid couplings.
1.
Flanged
2. Split
Coupler
3.
Keyed
4.
Friction
Flanged Coupling
Split Coupler
Â
In this
type of coupling , we use same process i.e. key will be used for fixing the
coupling with shaft and then coupling will be coupled together with bolts.
Keyed Coupler
Grooves will
be cut over the shaft and with the fixed member and we will use one key
for connecting two parts together.
Friction Coupling
Clutch not engaged Â
 
Clutch in engaged condition
Flexible coupling
Such
type of couplings are used for non aligned connecting member
1.
Constant Velocity
2. Universal
2. Universal
3.
Flexible
Constant Velocity
Universal
This
type of couplings are very suitable for connecting two members those are not
aligned and we may use this coupling up to misalignment angle 40 degrees.
Flexible Coupling
In
this type of coupling , both connecting shaft will be bolted over a rubber disc
and we may use this type of coupling where misalignment angle not more than 3
degree as only rubber disc flexibility will compensates the misalignment
angle.
We
studied coupling and key and these two parts are basic components in any
industry
Let us
go ahead towards another technical blog
Keep
reading and provide your feedback
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