This document discusses the fabrication of a spur gear. It begins with introducing gears and their uses, classifying spur gears and their applications. It then discusses gear terminology and provides examples. The document presents a problem of designing a spur gear to transmit 30hp at 1800rpm. It provides the solution, specifying cast iron material, an 8 pitch diameter, a 1.0625 inch face width, 20 teeth for the pinion and 24 teeth for the gear. Milling is selected as the manufacturing process due to its flexibility, accuracy and cost. Finally, a rendered image of the manufactured spur gear is presented.

1. Fabrication Of Spur
Gear
Supervised by
Md.Golam Kader
Professor,
Md Rasedul Islam
Lecturer,
Department of Mechanical
Engineering, KUET
Course ME 3118
Khulna University Of Engineering & Technology
Department of Mechanical Engineering
Submitted By
Md Rezowan Kabir [1205016]
Md Hasanuzzaman [1205017]
Md Abul Kashem Hemel [1205018]
Md Ashik Mahmud [1205019]
Saikat Biswas [1205020]

2. Chapter 1
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3. Objectives
To Study about gear.
To Study about the classification of gear.
To Study about spur gear.
Fabrication of spur gear.
To Study of advantages and disadvantages of
spur gear.
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4. Introduction
A gear is a rotating machine part having cut teeth, which mesh with
another toothed part to transmit torque, in most cases with teeth on
the one gear being of identical shape, and often also with that shape
on the other gear.
Two or more gears working in a sequence are called a gear train or,
in many cases, a transmission; such
Gear arrangements can produce a
mechanical advantage through a gear
ratio and thus may be considered a
simple machine.
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5. Introduction (Continued)
Gears are Used to Control Power Transmission in These Ways
1. Changing the direction through which power is transmitted (i.e.
parallel, right angles, rotating, linear etc.)
2. Changing the amount of force or torque
3. Changing RPM
When two gears mesh, and one gear is bigger than the other (even
though the size of the teeth must match), a mechanical advantage is
produced, with the rotational speeds and the torques of the two gears
differing in an inverse relationship.
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6. Types Of Gears
According to the position of axes of the shafts.
Parallel
1.Spur Gear
2.Helical Gear
3.Rack and Pinion
Intersecting
1.Bevel Gear
Non-intersecting and Non-parallel
1.worm and worm gears
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7. Spur Gear
Spur gears are the most commonly used gear type. They are
characterized by teeth which are perpendicular to the face of the
gear. Spur gears are by far the most commonly available, and
are generally the least expensive.
Teeth is parallel to axis of rotation
Transmit power from one shaft to another parallel shaft
least expensive
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8. Applications of Spur Gear
In mechanical systems where we’ll require simple design, more
efficient power transfer, and low speed applications where
noise does not matter, we should go for spur gears.
Spur gears have a wide range of applications. They are used in:
 Metal cutting machines
 Power plants
 Marine engines
 Mechanical clocks and
watches
 Fuel pumps
 Washing Machines
Gear motors and gear
pumps
 Rack and pinion
mechanisms
 Material handling
equipments
 Automobile gear boxes
 Steel mills
 Rolling mills
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9. Chapter 2
CONTENTS
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10. GEAR TERMINOLOGY
Pitch surface : The surface of the imaginary rolling cylinder
(cone, etc.) that the toothed gear may be considered to replace.
Pitch circle: A right section of the pitch surface.
Root (or dedendum) circle: The circle bounding the spaces
between the teeth, in a right section of the gear.
Addendum: The radial distance between the pitch circle and the
addendum circle.
Dedendum: The radial distance between the pitch circle and the
root circle.
Clearance: The difference between the dedendum of one gear and
the addendum of the mating gear.
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11. GEAR TERMINOLOGY(CON’D)
Face of a tooth: That part of the tooth surface lying outside the pitch
surface.
Flank of a tooth: The part of the tooth surface lying inside the pitch
surface.
Circular thickness (tooth thickness) : The thickness of the tooth
measured on the pitch circle. It is the length of an arc and not the
length of a straight line.
Tooth space: The distance between adjacent teeth measured on the
pitch circle.
Backlash: The difference between the circle thickness of one gear
and the tooth space of the mating gear.
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12. GEAR TERMINOLOGY(CON’D)
Module m: Pitch diameter divided by number of teeth. The pitch
diameter is usually specified in inches or millimeters; in the former
case the module is the inverse of diametral pitch.
Fillet : The small radius that connects the profile of a tooth to the root
circle.
Pinion: The smaller of any pair of mating gears. The larger of the pair
is called simply the gear.
Velocity ratio: The ratio of the number of revolutions of the driving
(or input) gear to the number of revolutions of the driven (or output)
gear, in a unit of time.
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13. GEAR TERMINOLOGY(CON’D)
Pressure angle: Pressure angle in relation to gear teeth, also known
as the angle of obliquity, is the angle between the tooth face and the
gear wheel tangent. It is more precisely the angle at a pitch point
between the line of pressure (which is normal to the tooth surface)
and the plane tangent to the pitch surface.
Fig: Pressure angle of spur gear[1]
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14. GEAR TERMINOLOGY
Fig2: Spur gear terminology[2] Fig3: Spur gear terminology[3]

15. PROBLEM
It is desired to transmit 30 hp at 1800 rpm of the pinion;
intermittent service; with light shock (§13.18); preferably not less
than 20, 20o
-full-depth teeth on the pinion; strength reduction
factor Kf = 1.25 should be conservative; mw =1.5 Decisions must be
made concerning the material and quality of cutting the teeth.
Since the design is for strength only, it will be convenient to
express Ft , Fd , vm ,face width b in terms of pitch Pd and arrange an
equation containing s and Pd convenient for iteration. Weak
material results in a relatively large pinion with high peripheral
speed. A very strong material may be unnecessarily expensive. On
a production bases carefully cut teeth should have a reasonable
cost. Specify material, accuracy of cutting, pitch, face width, and
tooth numbers.
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16. SOLUTION
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17. SOLUTION(CON’D)
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18. SOLUTION(CON’D)
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19. SOLUTION(CON’D)
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Pd = 8
b=8.5/Pd
Np
= 20 ,
Ng Np
=mw
Ng
=20*1.2=24
b=1.0625
Np
=20
Ng
=24
So the pitch diameter of the gear Pd
= 8
Face width b =1.0625 inch
Number of teeth = 24

20. Drawing & Dimensions
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21. Rendering Image
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22. Chapter 3
CONTENTS
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23. MATERIAL
1.Steel
2.Cast Iron
3.Stainless Steel
4.Aluminum
5.Bronze
6.Nylon
7.Non-metallic phenolic
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24. Why we choose Cast Iron?
• High tensile strength to prevent failure against static loads.
• High endurance strength to withstand dynamic loads.
• Low coefficient of friction.
• Good manufacturability.
• Low cost.
• High availability.
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25. MANUFACTURING PROCESS OF SPUR
GEAR
1.Casting
2.Milling
3. Broaching
4. Gear hobbing
5. Gear forming
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26. Why we choose Milling Process?
1. It is Compatible with All Materials
2. Flexible Use
3. Short Lead Times
4. Better accuracy
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27. Milling Process
This is one of the initial and best known and metal removal process
for making gears. This method requires the usage of a milling
machine. It is also to be noted that this method can produce nearly
all types of gears. The method involves the use of a form cutter,
which is passed through the gear blank to create the tooth gap. This
method is right now used only for the manufacture of gears
requiring very less dimensional accuracy. To put it correctly this
method is currently outdated.
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28. Milling Process
Fig: Milling Process
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29. Final Project
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Fig: Manufactured Spur Gear

30. References
[1] FAIRES VIRGIL MORING, “DESIGN OF MACHINE
ELEMENTS”, 4th
edition, The Macmillan Company, New
York/Collier-Macmillan Limited, London
[2] Jain R.K., “ Production Technology”, 16th
edition, 2-B, Nath
Market, Nai Sarak, Delhi-110006
[3]http://www.brighthubengineering.com/manufacturing-
technology/7118-gear-manufacturing-methods
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31. THANK YOUYOU
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