In this article, you’ll learn what are the different Gear Terminology and Terms used in gear with calculation.
Gear Terminology:
Following are the gear terminology and gear terms used in the description of gears:
- Pitch circle
- Pitch circle diameter
- Pressure angle
- Pitch point
- Pitch surface
- Addendum
- Dedendum
- Addendum circle
- Dedendum circle
- Base circle
- Circular pitch
- Diameter pitch
- Module
- Clearance
- Total Depth
- Working Depth
- Tooth thickness
- Tooth space
- The face of the tooth
- The flank of the tooth
- Top land
- Face width
- Profile
- Backlash
Explanation of Gear Terms
#1. Pitch circle.
Pich circle is the imaginary circle that rolls without slipping with a pitch circle of a mating gear.
#2. Pitch Circle Diameter.
The pitch circle diameter is the diameter of the pitch circle. It is also known as pitch diameter.
#3. Pressure angle.
Pressure angle is the angle between the common normal at the point of tooth contact and the common tangent to the pitch circle. The usual pressure angles are 14½° and 20°.
#4. Pitch point.
It is a common point of contact between two pitch circles.
#5. Pitch surface.
It is the surface of the imaginary rolling cylinder that the toothed gear may be considered to replace.
#6. Addendum.
The addendum is the radial distance of a tooth from the pitch circle to the top of the tooth.
#7. Dedendum.
Dedendum is the circle drawn through the bottom of the teeth. It is also called “root circle”.
#8. Addendum circle.
It is the circle drawn through the top of the teeth and it is concentric with the pitch circle.
#9. Dedendum circle.
It is the circle drawn through the bottom of the tooth. It is also called “root circle”.
#10. Base Circle.
The base circle of involute gear is the circle from which involute tooth profiles are determined.
#11. Circular pitch.
The circular pitch is the distance measured on the circumference of the pitch circle from a point of one tooth to the corresponding point on the next tooth. It is denoted by Pc.
Pc = πd/T
- D = diameter of the circle
- T = No. of teeth on the wheel
#12. Diametral Pitch.
It is the ratio of a number of teeth to the pitch circle diameter. It is indicated by Pd.
Pd = T/d = π/Pc
Pc = πd/T
Where,
- T= No. of teeth,
- d= Pitch circle diameter.
#13. Module.
The ratio between the pitch diameter and the number of teeth is known as the module. It is represented by m. m= d/T.
#14. Clearance.
Clearance is the difference between the dedendum of one gear and the addendum of the mating gear.
#15. Total Depth.
Total depth is the radial distance between the addendum and the dedendum of a gear. It is equal to the sum of addendum and dedendum.
#16. Working Depth.
It is the radial distance from the addendum circle to the clearance circle. It is equal to the sum of the addendum of the two meshing gears.
#17. Tooth thickness.
Tooth thickness is the width of the tooth measured along the pitch circle.
#18. Tooth space.
Tooth space is the width of space between the two adjacent teeth measured along the pitch circle.
#19. Face of the tooth.
It is the surface of the tooth above the pitch surface.
#20. Flank of the tooth.
The flank of the tooth is the surface of the tooth below the pitch surface.
#21. Top land.
The top land is the surface of the top of the tooth.
#22. Face width.
Face width is the width of the gear tooth measured parallel to its axis.
#23. Profile.
It is the curve formed by the face and flank of the tooth.
#24. Backlash.
Backlash is the difference between the thickness of a tooth and the width of a tooth space on which it meshes.