This document provides an overview of different types of gears including their key components and terminology. It discusses common gear types like spur gears, helical gears, bevel gears, and worm gears. For each type it provides examples of advantages and disadvantages as well as typical applications. The document also discusses gear materials and common modes of gear failure such as scoring, wear, pitting, plastic flow, and tooth fracture.

1. KUMARAGURU COLLEGE OF TECHNOLOGY
P15CCT104 - INTEGRATED MECHANICAL DESIGN
GEARS
Presented By,
RAGHUL S(17MCC006)

2. TABLE OF CONTENTS
 Introduction
 General Nomenclature
 Types Of Gears
 Gear Materials
 Gear Tooth Failure

3. INTRODUCTION:
 A gear is a wheel with teeth that mesh together with
other gears.
 Transmit motion by engaging teeth
 Two or more meshing gears, working in a
sequence, are called a gear train
 Used to change,
 Speed
 Torque
 Direction

4. GENERAL NOMENCLATURE

5. Face Width:
 The Face width of a gear is the length of teeth in an
axial plane.
Pressure Angle ( α ):
 Pressure angle is the leaning angle of a gear tooth, an
element determining the tooth profile.
Whole depth:
 The distance from the top of the tooth to the root; it is
equal to addendum plus dedendum or to working depth
plus clearance.
Working depth:
 Depth of engagement of two gears, that is, the sum of
their operating addendums.

6. Pitch circle:
 A Pitch circle is the curve of intersection of a pitch
surface of revolution and a plane of rotation.
Outside diameter:
 Diameter of the gear, measured from the tops of the
teeth.
Root diameter :
 Diameter of the gear, measured at the base of the tooth.
Clearance:
 Distance between the root circle of a gear and the
addendum circle of its mate.

7. Addendum:
 Radial distance between the pitch diameter and the
outside diameter.
Addendum circle:
 Coincides with the tops of the teeth of a gear and is
concentric with the standard pitch circle.
Dedendum:
 Radial distance from the depth of the tooth trough to the
pitch surface.
Dedendum Circle:
 The circle touching the bottom of the spaces between
the teeth of a gear wheel.

9. TYPES OF GEAR:
 Spur Gear
 Helical Gear
 Bevel Gear
 Worm Gear
 Rack And Pinion
 Herringbone Gear

10. SPUR GEAR:
 Most commonly used Gear type.
 Teeth are parallel to the axis of the gear.
 Transmit power from one shaft to other parallel
shaft.

11. Advantage:
Low Cost
Ease of manufacture
Availability
Disadvantage:
Only works with mating gear
Axis of each gear must be parallel
Applications:
Washing Machines, Rolling Mills, Marine
Engines.

12. HELICAL GEAR
 Teeth are at an angle to the gear axis
 This gradual arrangement makes helical gear
operate much more smoothly and quietly than spur
gear
 Can transmit power between Right angle or Parallel
Axis

13. Advantage:
Smooth and quiet due to gradual tooth
engagements
Parallel to perpendicular shaft arrangement
Disadvantage:
Difficult to Manufacture
Cost is High
Resulting axial thrust component
Applications:
Fertilizer industries, Printing industries, earth
moving industries, Conveyors, Elevators

14. BEVEL GEAR:
 Usefull when the direction of shaft location has to
be changed.
 Mounted on shaft that are 90deg apart, can also be
designed to work in other angles.
 Teeth can be straight, Spiral or Hypoid

15. Advantage:
Operate on Shafts intersecting at an Angle.
Sliding friction will be low.
Disadvantage:
Assembled with respective shaft precisely.
At high speed it will produce noise.
Applications:
Textile Machine, Sewing Machine.

16. WORM GEAR:
 Used when large Gear Reduction is needed.
 Have good intersecting property.
 Used widely in material Handling and transportation
machinery, machine tools etc…

17. Advantage:
Higher speed reduction could be secured;
speed reduction could be secured up to 300:1
Worm and worm gears operate silently
Disadvantage:
Manufacturing cost is high as compared with
manufacturing cost of bevel gear
Worm and worm gear set will have heavy
power losses.
Efficiency will be low
Applications:
 Tuning Instruments, Lifts/Elevators.

18. RACK AND PINION:
 Convert Rotational to Linear motion
 Round Gear – Pinion
Flat or Straight Gear – Rack
 Best example is Car Steering System.

19. Advantage:
Rack and pinion gives easier and more
compact control over the vehicle
Cheap, Compact, Robust.
Disadvantage:
The rack and pinion can only work with certain
levels of friction.
Applications:
Rack Elevators, Steering.

20. HERRINGBONE GEAR:
 Two helical gears that have been placed side by
side.
 Referred to as “double helical”.
 No thrust loading on the bearings

21. Advantage:
The double helical form balances the inherent
thrust forces.
Efficient transfer of torque and smooth motion
at very high rotational velocities.
Disadvantage:
High cost due to special gear shaping
equipment and special cutting tools.
Applications:
Used in Heavy Machinery.

22. GEAR MATERIALS:
 Numerous nonferrous alloys, cast irons, powder-
metallurgy and plastics are used in the manufacture
of gears.
 Steels - commonly used - high strength-to-weight
ratio and low cost.
 Plastics - cost or weight is a concern - Reduce
repair cost.

23. GEAR TOOTH FAILURE:
 Gear failure can occur in various modes.
 Care has to be taken to avoid such failures
 Types of Gear Tooth Failure:
 Scoring Failure
 Wear Failure
 Pitting Failure
 Plastic Flow
 Tooth Fracture

24. SCORING FAILURE:
 Occurs Due to Lubrication failure in Contact region
and metal to metal contact.
 Welding and tearing action resulting from metallic
contact removes the metal.
 Types of Scoring:
 Initial Scoring
 Moderate Scoring
 Destructive Scoring

25. Initial Scoring:
 Occurs by High spots left by previous machine.
 Lubrication failure at this point leads to Scoring
 Scoring stops when temperature, load and speed
remains unchanged.

26. Moderate Scoring:
 Occurs After initial scoring if the load, speed or oil
temperature increases, the scoring will spread over
to a larger area.
 Progresses at tolerable rate.

27. Destructive Scoring:
 If the load, speed or oil temperature
increases appreciably, then severe scoring sets in
with heavy metal will occur.
 Predominant over Pitch line since the lubrication
is least at that region.

28. WEAR FAILURE:
 Wear is a kind of tooth damage where a layers of
metal are removed more or less uniformly from the
surface.
 Tooth Thins and get weakened.
 Cause of gear tooth wear is
 Adhesive Wear
 Abrasive Wear
 Corrosion Wear

29. Adhesive Wear:
 Hard to detect.
 Occurs from start since the rate of wear is low.
 When the load and speed of operation are more
than mild wear conditions, moderate wear takes
place with higher rate.
 Occurs over long Period.

30. Abrasive Wear:
 Reason for the failure of open gearing and closed
gearing of machine operated in Abrasive materials.
 Depending on the size, shape and concentration of
the abrasives the wear will change.

31. Corrosion Wear:
 Due to the chemical action of the lubricating oil or
the additives.

32. PITTING FAILURE:
 Surface fatigue failure of the gear tooth.
 Occur due to repeated loading of tooth surface and
contact stress.
 Pit is formed.
 Impact load resulting from pitting may cause failure.
 Types of Pitting
 Initial Pitting
 Progressive Pitting

33. Initial Pitting:
 Small pits of 25 to 50 μm deep are formed just
below the pitch line.
 the load gets distributed over a larger surface area
and stress comes down.
 Common with medium hard Gears.

34. Progressive Pitting:
 High load and corrective action of initial pitting
leads to Progressive Pitting.
 Pitting begins on the tooth flanks near the line
along the tooth passing through the pitch point.
 Very rare in tooth Face.

35. PLASTIC FLOW:
 Occurs due to sliding action of Gear.
 Surface deformation Occurs due to yielding of
surface.
 But occurs only in heavy loading Case.

36. TOOTH FRACTURE:
 Dangerous kind of gear failure leads to disablement
of drive and frequently to damage of other
components.
 Occurs over a long a period of time.
 Tooth failure may result low-cycle fatigue, Repeated
cyclic load

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