HELICAL MILLING

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• Q1: Define Helical Milling.
  Ans: Helical Milling is a process of cutting a helical groove or thread on a cylindrical surface using a milling machine where the cutter moves in a spiral path around the workpiece.
• Q2: Define Helical Gear.
  Ans: A Helical Gear is a cylindrical gear with teeth cut at an angle to the axis, forming a helix. This allows gradual engagement and smoother motion compared to spur gears.
• Q3: State some important features of Helical Gear.
  Ans: Important features of Helical Gears are:

  • ➔ Teeth are cut at an angle (helix angle) to the axis.
  • ➔ They have a longer contact ratio than spur gears.
  • ➔ Smoother and quieter operation.
  • ➔ Can transmit higher loads.
  • ➔ Available in parallel and crossed shaft arrangements.
• Q4: State some uses of Helical Gear.
  Ans: Uses of Helical Gears:

  • ➔ Automotive transmissions
  • ➔ Industrial machinery
  • ➔ Conveyors
  • ➔ Elevators
• Q5: Write some uses of Helical Gear in Power Transmission.
  Ans: In Power Transmission, Helical Gears are used for:

  • ➔ High-speed applications
  • ➔ Heavy load carrying machines
  • ➔ Smooth and quiet operation
  • ➔ Automotive gearboxes
• Q6: What is the lead of Helical Gear? Write its formula.
  Ans: The lead of a Helical Gear is the distance a point on the tooth travels along the axis in one complete revolution.
  Formula:
  
  Lead (L) = π × Module × cos(β) / sin(α)
  
  Where:
  Module = gear module
  β = helix angle
  α = pressure angle
• Q7: What is the lead of the Milling Machine?
  Ans: The lead of a Milling Machine is the linear distance moved by the worktable along its axis in one revolution of the table screw.
• Q8: Write the formula of lead of the Milling Machine?
  Ans: The formula is as follows:
  
  Lead (L) = Pitch of table screw × Number of starts of screw
• Q9: Briefly discuss the angular setting of Work Table.
  Ans: The angular setting of a work table determines the angle at which the workpiece is tilted for milling.
  It allows cutting of helical grooves or inclined surfaces by rotating the table to the required angle before starting the milling operation.
• Q10: Calculate Lead of Milling Machine if table screw has a pitch of 5mm.
  Ans: Given: Pitch of table screw = 5 mm, single start screw.
  Lead (L) = Pitch × Number of starts
  L = 5 mm × 1
  L = 5 mm
• Q11: Calculate Lead of Milling Machine if table screw has a pitch of 8mm.
  Ans: Given: Pitch = 8 mm, single start screw.
  Lead (L) = Pitch × Number of starts
  L = 8 mm × 1
  L = 8 mm
• Q12: Calculate change gears required to cut helix having lead of 400mm on work piece using standard change gears if table screw has a pitch of 5mm.
  Ans: Given: Lead of workpiece (Lw) = 400 mm, pitch of table screw (Ps) = 5 mm
  Step 1: Find the ratio of workpiece lead to table screw lead
  Ratio = Lw / Ps = 400 / 5 = 80
  Step 2: Use standard change gears to achieve this 80:1 ratio in combination.
  Step 3: Select gears so that Gear Train Ratio = 80:1
• Q13: Calculate Lead of Milling Machine if table screw has a pitch of 6mm.
  Ans: Given: Pitch = 6 mm, single start screw.
  Lead (L) = Pitch × Number of starts
  L = 6 mm × 1
  L = 6 mm
• Q14: Calculate Circular Pitch of 02 Module.
  Ans: Circular Pitch (p) = π × Module
  Given: Module = 2
  p = π × 2 = 6.283 mm
• Q15: Calculate Pitch Diameter of 33 tooth helical gear of 02 Module at 15 degree angle.
  Ans: Formula:
  
  Pitch Diameter (d) = Module × Number of teeth / cos(β)
  
  Given:
  Module = 2, Teeth = 33, Helix angle β = 15°
  d = 2 × 33 / cos(15°)
  cos(15°) ≈ 0.966
  d = 66 / 0.966 ≈ 68.36 mm
• Q16: Calculate Pitch Diameter of 25 tooth helical gear of 01 Module at 30 degree angle.
  Ans: Formula:
  
  Pitch Diameter (d) = Module × Number of teeth / cos(β)
  
  Module = 1, Teeth = 25, β = 30°
  cos(30°) = 0.866
  d = 1 × 25 / 0.866 ≈ 28.87 mm
• Q17: Define Helix.
  Ans: A Helix is a three-dimensional curve shaped like a screw thread or spiral, formed by a point moving around a cylinder at a constant angle to its axis.
• Q18: What do you understand about Right-angle non-intersecting shafts?
  Ans: Right-angle non-intersecting shafts are shafts arranged at 90° to each other but do not meet at a point. Motion is transmitted using bevel or hypoid gears.
• Q19: Calculate Tooth Thickness of gear for 2.5 Module if the pressure angle is 20 degrees.
  Ans: Formula:
  
  Tooth Thickness (t) = (π × Module) / 2
  
  Module = 2.5
  t = (π × 2.5) / 2
  t = 7.854 / 2 ≈ 3.927 mm
• Q20: Calculate Depth of Tooth of gear for 1.75 Module if the pressure angle is 20 degrees.
  Ans: Formula:
  
  Depth of Tooth (h) = 2.25 × Module
  
  Module = 1.75
  h = 2.25 × 1.75
  h ≈ 3.9375 mm