Senior Draughtsman Mech Interview Questions and Answers

The formula for calculating the dimensions of spur gears is based on the module, number of teeth, and pitch diameter.

• Formula for calculating the pitch diameter: PD = Module x Number of Teeth

• Formula for calculating the outside diameter: OD = (Number of Teeth + 2) x Module

• Formula for calculating the addendum: Addendum = Module

• Formula for calculating the dedendum: Dedendum = 1.25 x Module

• Formula for calculating the clearance: Clearance = 0.25 x Module

Formulae of gears involve calculations for gear ratio, pitch diameter, and tooth profile.

• Gear ratio formula: Number of teeth on driven gear / Number of teeth on driving gear

• Pitch diameter formula: Number of teeth / Diametral pitch

• Tooth profile formula: Involves calculations for involute curve and pressure angle