Gear Technical Reference – The Role Gears are Playing

Gears are used in various types of machinery as a transmission component.
The reasons why gears are so widely used to this day can best be described by these facts:

  • Gears range in size from miniature instrument installations, such as watches, to large, powerful gears used in turbine drives for ocean liners
  • Gears offer positive transmission of power
  • Transmission ratio can be freely controlled with high accuracy by changing the number of gear teeth
  • By increasing or decreasing the number of paired gears, enables you to adjust position transmission with very high angular or linear accuracy
  • Gears can couple power and motion between shafts whose axis are parallel, intersecting or skew


This technical reference provides the fundamentals of both theoretical and practical information.
When you select KHK products for your applications, please make use of the KHK catalog and this technical reference.

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Table of Contents

  1. Gear Types and Terminology
    1.1 Type of Gears
    1.2 Symbols and Terminology
  2. Gear Trains
    2.1 Single – Stage Gear Train
    2.2 Two – Stage Gear Train
  3. Involute Gear Profile
    3.1 Module Sizes and Standards
    3.2 The Involute Curve
    3.3 Meshing of Involute Gear
    3.4 The Generating of a Spur Gear
    3.5 Undercutting
    3.6 Profile Shifting
    3.7 Gear Tooth Modifications
  4. Calculation of Gear Dimensions
    4.1 Spur Gears
    4.2 Internal Gears
    4.3 Helical Gears
    4.4 Bevel Gears
    4.5 Screw Gears
    4.6 Cylindrical Worm Gear Pair
  5. Tooth Thickness
    5.1 Chordal Tooth Thickness Measurement
    5.2 Span Measurement of Teeth
    5.3 Measurement Over Rollers
  6. Gear Backlash
    6.1 Definition of Backlash
    6.2 Backlash Relationship
    6.3 Tooth Thickness and Backlash
    6.4 Gear Train and Backlash
    6.5 Methods of Reducing Backlash
  7. Accuracy of Gears
    7.1 Accuracy of Spur and Helical Gears
    7.2 Accuracy of Bevel Gears
  8. Mounting Accuracy of Gears
    8.1 Accuracy of Center Distance
    8.2 Axial Parallelism
    8.3 Features of Tooth Contact
  9. Gear Materials
    9.1 Types of Gear Materials
    9.2 Heat Treatments
  10. Gear Strength and Gear Durability
    10.1 Bending Strength of Spur and Helical Gears
    10.2 Surface Durability of Spur and Helical Gears
    10.3 Bending Strength of Bevel Gears
    10.4 Surface Durability of Bevel Gears
    10.5 Surface Durability of Worm Gear
  11. Design of Plastic Gears
    11.1 The Properties of Nylon and Duracon
    11.2 Strength of Plastic Gears
  12. Gear Forces
    12.1 Forces in a Parallel Axes Gear Mesh
    12.2 Forces in an Intersecting Axes Gear Mesh
    12.3 Forces in a Nonparallel and Nonintersecting Axes Gear Mesh
  13. Lubrication of Gears
    13.1 Methods of Lubrication
    13.2 Gear Lubricants
  14. Damage to Gears
    14.1 Gear Wear and Tooth Surface Fatigue
    14.2 Gear Breakage
    14.3 Types of Damage and Breakage
  15. How to reduce Gear Noise
  16. Determining the Specifications of Gears
    16.1 A Method for Determining the Specifications of a Spur Gear
    16.2 A Method for Determining the Specifications of a Helical Gear
  17. Gear Systems
    17.1 Planetary Gear System
    17.2 Hypocycloid Mechanism
    17.3 Constrained Gear System

Special contents for website

Gear Design – A page of Gear Design
Gear Pump – A page of Gear Pump

Related links :
The ABC’s of Gears / Basic Guide – B
Introduction to Gears
Spur Gears
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