DESIGN OF KEYS

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• Q1: Define Key.
  Ans: Key is a part of mild steel that is inserted between a shaft and a hub to connect them together.
  It prevents relative rotation between the shaft and the hub and helps in transmitting torque.
• Q2: Define Keyway.
  Ans: Keyway is the slot or groove made in the shaft or hub to accommodate the key.
• Q3: State the types of Keys.
  Ans: The types of keys are as follows:

  • ➔ Sunk Keys
  • ➔ Saddle Keys
  • ➔ Tangent Keys
  • ➔ Round Keys
  • ➔ Splines
• Q4: Define Sunk Keys.
  Ans: Sunk keys are the keys that are fitted half in the shaft and half in the hub.
  They are commonly used for transmitting torque between the shaft and the hub.
• Q5: State the types of Sunk Keys.
  Ans: The types of sunk keys are as follows:

  • ➔ Rectangular Sunk Keys
  • ➔ Square Sunk Keys
  • ➔ Gib Head Sunk Keys
  • ➔ Woodruff Sunk Keys
  • ➔ Parallel Sunk Keys
  • ➔ Feather Sunk Keys
• Q6: Define Rectangular Sunk Keys.
  Ans: Rectangular sunk keys are rectangular in shape and are fitted partly in the shaft and partly in the hub to transmit power.
• Q7: Define Square Sunk Keys.
  Ans: Square sunk keys are square in cross-section and are used to connect the shaft and hub for power transmission.
• Q8: Define Gib Head Sunk Keys.
  Ans: Gib head sunk keys are rectangular sunk keys with a head at one end which helps in easy removal of the key.
• Q9: Define Woodruff Sunk Keys.
  Ans: Woodruff sunk keys are semicircular keys that fit into a circular recess in the shaft.
  They are commonly used in machine tools and automobile shafts.
• Q10: Define Parallel Sunk Keys.
  Ans: Parallel sunk keys have parallel top and bottom surfaces and are used for transmitting torque between the shaft and hub.
• Q11: Define Feather Sunk Keys.
  Ans: Feather sunk keys are special types of sunk keys that allow axial movement between the shaft and the hub while transmitting torque.
• Q12: Define Saddle Keys.
  Ans: Saddle keys are keys that are placed on the shaft without cutting a keyway in the shaft.
  They transmit torque mainly through friction.
• Q13: State the types of Saddle Keys.
  Ans: The types of saddle keys are as follows:

  • ➔ Flat Saddle Keys
  • ➔ Hollow Saddle Keys
• Q14: Define Flat Saddle Keys.
  Ans: Flat saddle keys have a flat bottom surface and rest on the shaft without any keyway.
• Q15: Define Hollow Saddle Keys.
  Ans: Hollow saddle keys have a curved bottom surface that fits on the shaft surface for better grip.
• Q16: Define Tangent Keys.
  Ans: Tangent keys are keys placed tangentially to the shaft and are usually used in pairs to transmit heavy loads.
• Q17: Define Round Keys.
  Ans: Round keys are cylindrical pins inserted into drilled holes in the shaft and hub to prevent relative motion.
• Q18: Define Splines
  Ans: Splines are multiple keys formed on the shaft that fit into corresponding grooves in the hub.
  They are used to transmit high torque.
• Q19: State the forces acting on the Sunk key.
  Ans: The forces acting on the sunk key are as follows:

  • ➔ Shear force
  • ➔ Crushing force
• Q20: Define Shearing of Key.
  Ans: Shearing of key occurs when the applied torque produces a shear force that tends to cut the key across its cross-section.
• Q21: Define Crushing of Key.
  Ans: Crushing of key occurs when compressive forces act between the key and the hub or shaft, causing deformation of the key surface.
• Q22: What is the difference between a Key and a Cotter?
  Ans: The difference between key and cotter is as follows:

  • ➔ Key is used to connect a shaft and hub to transmit torque.
  • ➔ Cotter is used to connect two co-axial rods subjected to axial forces.
• Q23: Name the stresses produced in keys.
  Ans: The stresses produced in keys are as follows:

  • ➔ Shear Stress
  • ➔ Crushing Stress
• Q24: If the material of the key and shaft are the same then what will be the length of key?
  Ans: If the material of the key and shaft are the same, then the length of the key is equal to 1.5 times the diameter of the shaft.