# Shaft and Coupling Basic | Interview question and Answers

1. What is a shaft?

A shaft is a rotating machine element, which transits power from one point to another point.

2. What are the types of shaft?

• Line shaft
• Spindle
• Stub shaft
• Counter shaft

3. What are the types of rigidity?

• Torsional rigidity
• Lateral rigidity

4. Why a hollow shaft has greater strength and stiffness than solid shaft of equal weight?

Stresses are maximum at the outer surface of a shaft. Hollow shaft has almost all the material concentrated at the outer circumference and so has a better strength and stiffness for equal weight.

5. Why is maximum shear stress theory used for shaft?

Since, the shaft is made of ductile material; maximum shear stress thus is used

6. What is the significance of slenderness ratio in shaft design?

If slenderness ratio is increased the shaft deviates from its “stub” behavior And it is essential to consider bucking while designing the shaft.

7. Define the term critical speed?

The speed at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite, is known as critical speed

8.What is a key?

A key is a device which is used for connecting two machine parts for preventing relative motion of rotation with respect to each other.

9. What are the types of key?

• Tangent key
• Sunk key
• Round key and taper pins.

10.What is the main use of woodruff keys?

A woodruff key is used to transmit small value of torque in automotive and machine tool industries. The keyway in the shaft is milled in a curved shape whereas the key way in the hub is usually straight.

11.What types of stress are developed in the key?

Shear stress and crushing stress

12.Classify crankshafts.

Single throw crankshafts
Multi throw crankshafts

13. What are functions of crankshafts?

Crankshafts are used to convent lottery motion into reciprocating motion.

14. What are the materials used for crankshafts?

For I C engine or mild steel and automobile.

15. What is coupling?

The elements which join two shafts are coupling. It is used to connect sections of long transmissions shaft to the shaft of a driving machine. Couplings are used to connect sections of long transmission shafts and to connect the shaft of a driving machine to the shaft of a driven machine.

16. What is the function of a coupling between two shafts?

Couplings are used to connect sections of long transmission shafts and to connect the shaft of a driving machine to the shaft of a driven machine.

17. Under what circumstances flexible couplings are used?

They are used to join the abutting ends of shafts when they are not in exact alignment.They are used to permit an axial misalignment of the shafts without under absorption of the power, which the shafts are transmitting

18.Where are flexible couplings used?

• Vehicle
• Stationery machinery
• Automotive drives
• Machine tools

19.What is the material used for flange or flange coupling?

Cast iron

20.What is the advantage of gear coupling?

Gear coupling is a grid coupling with some flexibility because of using curved external teeth Strength of gear coupling is very high. Most compact coupling for high power transmission.