Following are the gear terminology or gear terms used to about gears:
- Pitch circle
- Pitch circle diameter
- Pitch point
- Pitch surface
- Pressure angle
- Addendum circle
- Dedendum angle
- Circular pitch
- Diameter pitch
- Total Depth
- Working Depth
- Tooth thickness
- Tooth space
- The face of the tooth
- The flank of the tooth
- Top land
- Face width
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
Pitch circle diameter is the diameter of the pitch circle. It is also known as pitch diameter.
3. Pitch point
It is a common point of contact between two pitch circles.
4. 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°.
5. Pitch surface
It is the surface of the imaginary rolling cylinder that the toothed gear may be considered to replace.
The addendum is the radial distance of a tooth from the pitch circle to the top of the tooth.
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. 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
11. 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.
A module is the ratio of pitch circle diameter by m. m= d/T
Clearance is the difference between the dedendum of one gear and the addendum of the mating gear.
14. 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.
15. 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.
16. Tooth thickness
Tooth thickness is the width of the tooth measured along the pitch circle.
17. Tooth space
Tooth space is the width of space between the two adjacent teeth measured along the pitch circle.
18. Face of the tooth
It is the surface of the tooth above the pitch surface.
19. Flank of the tooth
The flank of the tooth is the surface of the tooth below the pitch surface.
20. Top land
The top land is the surface of the top of the tooth.
21. Face width
Face width is the width of the gear tooth measured parallel to its axis.
It is the curve formed by the face and flank of the tooth.
Backlash is the difference between the thickness of a tooth and the width of a tooth space on which it meshes.
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