GEAR TERMINOLOGY & SPUR GEAR CALCULATIONS

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• Q1: What is a Gear?
  Ans: A gear is a machine element having teeth which is used to transmit motion and power from one shaft to another.
• Q2: What is a Spur Gear?
  Ans: A spur gear is a type of gear having straight teeth parallel to the axis. It is used to transmit motion between parallel shafts.
• Q3: Name some Gear Terminologies.
  Ans: Some important gear terminologies are:

  • ➔ Pitch Circle
  • ➔ Pitch Diameter
  • ➔ Addendum
  • ➔ Dedendum
  • ➔ Module
  • ➔ Circular Pitch
  • ➔ Tooth Thickness
• Q4: What is Dendum?
  Ans: Dendum (Dedendum) is the distance from the pitch circle to the root of the gear tooth.
  Formula:
  
  Dedendum = 1.166M
• Q5: What is Addendum? Write the formula.
  Ans: Addendum is the distance from the pitch circle to the top of the gear tooth.
  Formula:
  
  Addendum = 1M
• Q6: What is Tooth Thickness of gear? Write a formula.
  Ans: Tooth thickness is the width of a gear tooth measured along the pitch circle.
  Formula:
  
  Tooth Thickness = 1.57M
• Q7: What is a Tooth Gap?
  Ans: Tooth gap is the space between two adjacent gear teeth.
• Q8: What is a Pitch Diameter? Write the formula.
  Ans: Pitch diameter is the diameter of the pitch circle of the gear.
  Formula:
  
  Pitch Diameter = M × Z
• Q9: What is a Root Diameter? Write the formula.
  Ans: Root diameter is the diameter of the circle passing through the bottom of gear teeth.
  Formula:
  
  Root Diameter = D - 2 × Dedendum
• Q10: What is a Module? Write the formula.
  Ans: Module is the ratio of pitch diameter to number of teeth.
  Formula:
  
  M = D / Z
• Q11: What is Clearance?
  Ans: Clearance is the distance between the top of one gear tooth and the bottom of the mating tooth space.
  Formula:
  
  Clearance = 0.166M
• Q12: What is Gear Blank?
  Ans: Gear blank is the raw cylindrical piece of metal on which gear teeth are cut.
• Q13: What is a Rack?
  Ans: A rack is a straight gear having teeth cut on a flat surface. It is used to convert rotary motion into linear motion.
• Q14: Write the calculation for Spur Gear.
  Ans: Basic calculations for spur gear:

  • ➔ Pitch Diameter = M × Z
  • ➔ Addendum = M
  • ➔ Dedendum = 1.166M
  • ➔ Clearance = 0.166M
  • ➔ Outside Diameter = (Z + 2)M
  • ➔ Tooth Thickness = 1.57M
  • ➔ Circular Pitch = π × M
• Q15: A spur gear of 20 teeth is cut with 02 Module on a milling machine. Calculate Depth of Teeth, Cutter #, Outside diameter and Indexing.
  Ans: Given:
  Z = 20, M = 2
  
  Step 1: Depth of Teeth
  Depth = 2.166M
  = 2.166 × 2 = 4.332 mm
  
  Step 2: Cutter Number
  For 20 teeth → Cutter No. = 6
  
  Step 3: Outside Diameter
  OD = (Z + 2)M
  = (20 + 2) × 2 = 44 mm
  
  Step 4: Indexing
  Indexing = 40 / Z
  = 40 / 20 = 2 turns
• Q16: What will be the circular pitch of 02 Module?
  Ans: Formula:
  
  Circular Pitch = π × M
  
  = 3.14 × 2
  = 6.28 mm
• Q17: What will be the circular pitch of the 1.5 Module?
  Ans: Formula:
  
  Circular Pitch = π × M
  
  = 3.14 × 1.5
  = 4.71 mm
• Q18: What will be the pitch diameter of 02 Module of 80 teeth?
  Ans: Formula:
  
  D = M × Z
  
  = 2 × 80
  = 160 mm
• Q19: What will be the pitch diameter of gear of the 1.5 Module of 60 teeth?
  Ans: Formula:
  
  D = M × Z
  
  = 1.5 × 60
  = 90 mm
• Q20: What will be the pitch diameter of spur gear of 01 Module of 100 teeth?
  Ans: Formula:
  
  D = M × Z
  
  = 1 × 100
  = 100 mm