Common terms used:

**1. Pitch cone.** It is a cone containing the pitch elements of the teeth.

**2. Cone centre.** It is the apex of the pitch cone. It may be defined as that point where the axes of two mating gears intersect each other.

**3. Pitch angle**. It is the angle made by the pitch line with the axis of the shaft. It is denoted by ‘θP’.

**4. Cone distance.** It is the length of the pitch cone element. It is also called as a pitch cone radius. It is denoted by ‘OP’. Mathematically, cone distance or pitch cone radius,

**5. Addendum angle.** It is the angle subtended by the addendum of the tooth at the cone centre. It is denoted by ‘α’ Mathematically, addendum angle,

where a = Addendum, and OP = Cone distance.

**6. Dedendum angle.** It is the angle subtended by the dedendum of the tooth at the cone centre. It is denoted by ‘β’. Mathematically, dedendum angle,

where d = Dedendum, and OP = Cone distance.

**7. Face angle.** It is the angle subtended by the face of the tooth at the cone centre. It is denoted by ‘φ’. The face angle is equal to the pitch angle plus addendum angle.

**8. Root angle.** It is the angle subtended by the root of the tooth at the cone centre. It is denoted by ‘θR’. It is equal to the pitch angle minus dedendum angle.

**9. Back (or normal) cone.** It is an imaginary cone, perpendicular to the pitch cone at the end of the tooth.

**10. Back cone distance.** It is the length of the back cone. It is denoted by ‘RB’. It is also called back cone radius.

**11. Backing.** It is the distance of the pitch point (P) from the back of the boss, parallel to the pitch point of the gear. It is denoted by ‘B’.

**12. Crown height.** It is the distance of the crown point (C) from the cone centre (O), parallel to the axis of the gear. It is denoted by ‘HC’.

**13. Mounting height.** It is the distance of the back of the boss from the cone centre. It is denoted by ‘HM’.

**14. Pitch diameter.** It is the diameter of the largest pitch circle.

**15. Outside or addendum cone diameter.** It is the maximum diameter of the teeth of the gear. It is equal to the diameter of the blank from which the gear can be cut. Mathematically, outside diameter,

**16. Inside or dedendum cone diameter.** The inside or the dedendum cone diameter is given by

Dd = DP – 2d cos θP

where Dd = Inside diameter, and

d = Dedendum

**Design procedure for Bevel Gear**

**17. Calculation of gear ratio (i) and pitch angle:**

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