Shaft & keys (machine design & industrial drafting )

Subject :- MDID (2141907)
Topic :- Shaft & Keys
Guided By :- Mr. Rudraduttsinh Parmar
(Assistant professor)
Prepared By :- 150990119029 Keval Patel
150990119030 Krupal Patel
150990119031 Mayur Patel
150990119032 Meet Patel
150990119033 Parthiv Patel

Types of shaft
• Hollow shape • Solid shaft
Based On Shape

Transmitting Shafts
 Line shaft :-
It is use to transmit the power to several
machine.
 Stub shaft :-
When shaft is an integral part of the
machine or engine is called stub shaft.
 Counter shaft :-
A shaft that connect to prime mover to
line of machine is called counter shaft.
Based on Application

Machine Shaft :-
When shaft is an integral part of the
machine or engine is called machine shaft.
Spindle shaft :-
A short hollow shaft having
application of transmitting the power to tool
or a machine is called spindle shaft.

Based on Construction
Rigid shaft :-
It is a shaft which cannot be bend or
deformed out of shape during transmission of
rotary motion between two object or
machine.
Flexible shaft:-
It is a shaft which is partially
deformed in a manner not to affect the
transmission of motion is known as flexible
shaft.

Difference b/w shaft , spindle, axle
Sr No. Shafts Spindle Axle
1 Shaft is a rotating
member.
Spindle is a rotating
member.
Axel is a non-
rotating member
2 The purpose of shaft is to
transmit the torque and
to support the
transmission elements .
The spindle is a short
rotating shaft which is an
integral part of the
machine.
The purpose of an
axel is only to
support the
transmitting
elements .
3 Shaft is subjected to
torque , bending moment
or axial force
Spindle is subjected to
bending moment and / or
axial force
Axle is subjected to
bending moment
and / or axial force
4 Example :- Line shaft ,
counter shaft , spindle ,
crankshaft etc.
Example :- Lathe machine
spindle , drilling machine
spindle, milling machine
spindle etc.
Example:- Front
axle car , wheel axle
of motorcycle etc.

Design of shaft based on bending moment
for solid shaft
so,
And,

for hollow shaft
M=bending moment
I=moment of inertia
=bending stress
Y=

EXAMPLE:-Find the diameter of solid shaft to transmitte 25
kw at 225 r.p.m the allowable shear stress is equal to 50 mpa.
If we used hollow shaft in case of solid shaft then find the
inside & outside diameter of the shaft when the ratio of the
inside to outside diameter is equal to 3:4.
ANSWER:-
Given data
d=?
P=25kw
N=225 r.p.m
τ=50 mpa

Shaft & keys (machine design & industrial drafting )

DESIGN OF SHAFT BASED ON ASME
CODE
In most of the case shafts are not under constant Torque &
Bending.

Example .
 A mild steel shaft transmits 20 kW at 200 rpm.
 It carries a central load of 900N and is simply
supported between the bearings 2.5 m
apart.
 Determine the size of the shaft,
 If the allowable shear stress is 42 MPa and the maximum tensile or
compressive stress is
not to exceed 56 MPa.
 What size of the shaft will be required,
 if it is subjected to gradually applied loads.
DATA:
13

 maximum bending moment of a
simply supported shaft carrying a
central load,
Putting values in equation eq: 1
………… EQ: 1
14

We know that the equivalent bending moment,
………… eq: 2
Putting values in equation eq: 2
Taking the larger of the two values, we have
15

2.Size of the shaft when subjected to gradually applied load
Putting values of M, T, and other constants
in above equation
Putting value of Te in equation no 3
…………equation no 3
for rotating shafts with gradually applied loads
16

We know that the equivalent bending moment,
Putting values in above equation eq
Taking the larger of the two values, we have
17

Shafts Subjected to Combined Twisting
Moment and Bending Moment
When the shaft is subjected to combined twisting moment and bending moment, then the
shaft must be designed on the basis of the two moments simultaneously. Various theories
have been suggested to account for the elastic failure of the materials when they are
subjected to various types of combined stresses. The following two theories are important
from the subject point of view :
1. Maximum shear stress theory or Guest's theory. It is used for ductile materials such
as mild steel.
2. Maximum normal stress theory or Rankine’s theory. It is used for brittle materials
such as cast iron.
Let τ = Shear stress induced due to twisting moment, and
σb = Bending stress (tensile or compressive) induced due to bending moment.
According to maximum shear stress theory, the maximum shear stress in the shaft,

Substituting the values of τ and σb from Art. 14.9 and Art. 14.10, we have

What is key ?????
 A key is a machine
element used to connect a rotating
machine element to a shaft.
It is always inserted parallel to
the exist of the shaft.
A keyway is a slot in a shaft
and hub of the pulley to
accommodate a key.

Sunk key
• The sunk key are provided half in the keyway of the shaft
and half in the keyway of the hub .
• The sunk key are of the following types:
1. Rectangular key
2. Square key
3. Parallel key
4. Gib-Head key
5. Feather key
6. Woodruff Key

Rectangular Key
• A key is a piece of mild steel inserted between the shaft and
hub of the pulley to connect these together in order to prevent
relative motion between them.
The key has taper 1 in 100 on the top side only.

Square Key
• The only difference between a rectangular sunk key and a
square sunk key is that its width and thickness are equal.
i.e , W=t=d/4

Parallel key
• The parallel sunk key may be of rectangular or square
section uniform in width and thickness throughout.
• It may be noted that a parallel key is a taperless and is used
where the pulley, gear or other mating piece is required to
solid along the shaft.

Gib-Head Key
• It is a rectangular sunk key with a head at one end known as
Gib-Head Key.
• It is usually provided to facilitate and removal of key.

Feather key
• A key attached to one member of a
pair and which permits relative axial
movement is known as feather key.
• It is a special type of parallel key
which transmits a turning movement
and also permits axial movement.

Woodruff Key
 The woodruff key is an easily
adjustable key.
 It is piece from a cylindrical disc
having segmental cross-section in front
view of figure.
 This key is largely used in machine
tool and automobile construction.

Hollow Saddle Key :-
 A Hollow saddle key is a taper
key which fits in a keyway in the
hub and the bottom of the key is
shaped to fit the curved surface of
the shaft.
•It is used as a temporary fastening
in fixing and setting cams etc.

Tangent Keys
 The tangent key are fitted in a pair at
right angles.
 Each key is to withatand torsion in
one direction only.
 sThey are used in large heavy duty
shaft.

Round key
 The round keys, are circular in section and fit into holes
drilled partly in the shaft and partly in the hub.
 They have advantage that their keyways may be drilled and
reamed after the mating parts have been assembled.

Splines
 Sometimes, keys are made integral with the shaft which fit
in the keyways broached in the hub. Such shafts are known as
splined shafts.
 The Splined shaft are used when the forces to be transmitted
is large in proportional to the size of the shaft.

Shaft & keys (machine design & industrial drafting )

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