Shaft vs Axle: What is the difference?

What Is A Shaft?

A shaft is described as a rotating machine element, usually circular in cross-section, which is used to transmit power from one part to another, or from a machine that produces power to a machine that absorbs power.Shaft accepts and drives gears, pulleys, sprockets, and other rotary power elements.

Shaft form the important element of machines. They support rotating parts like gears and pulleys and are themselves supported by bearings resting in the rigid machine housing.

The shafts perform the function of transmitting power from one rotating member to another supported by it or connected to it. Thus, they are subjected to torque due to power transmission and bending moment due to the reactions of the members that are supported by them.

Shafts are mainly classified into two types.

  • Transmission shafts; which are used to transmit power between the source and the machine absorbing power; e.g. counter shafts and line shafts.
  • Machine shafts; which are the integral part of the machine itself; e.g. crankshaft.

What is an Axle?

Axle is a rotating/non-rotating member that support wheels, pulley, etc and is designed for only bending moment. It does not transmit torque. In other words, an axle is not twisted, it only bends.

On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle is supported. In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle. 

Axles are essential components of any vehicle and come in three main types: front, rear, and stub.

  • Rear Axle: This axle is responsible for delivering power to the driving wheels. It comes in two halves, known as half shafts, which are connected by the differential. In most cases, rear axles are live, meaning they rotate with the vehicle’s wheels.
  • Front Axle: Located in the front of the vehicle, this axle is responsible for assisting with steering and processing shocks from the uneven surface of the road. They have four main parts, which are the beam, the swivel pin, the track rod, and the stub axle. Front axles must be as sturdy as possible, and that’s why they’re usually made from carbon steel or nickel steel.
  • Stub Axle: Stub axles are attached to the vehicle’s front wheels, with kingpins connecting these axles to the front axle.

Difference between Shaft And Axle

Shaft refers to a member, usually of circular cross-section, which supports gear, sprockets, wheel, rotors, etcAxle is a rotating/non-rotating member that support wheels, pulley, etc 
Shaft is for Transmission of Power And Motion.Axle is for Wheel Support.
Shaft is subjected to bending moment, twisting moment and sometimes the axial loads. Axle subjected to only bending moments.
Shafts are the used to transfer torque and bending moment to another member by means of rotation.It does not transmit torque. In other words, an axle
is not twisted it only bends.
The shaft can take a load on shaft circumference.Axle can take the load at the centre or any of its circumference.
The shaft is used for rotary motion.Axle is used for linear or angular motion.
Shaft transfers power from the transmission to the rear differential gearbox.Axle transfer power from the rear differential gearbox to the wheels.
A shaft is a hollow steel tube of greater diameter than an axle shaft and with universal joints on each end.Axle is made by solid-steel rods with teeth cut into their ends.
The shaft can be meant for balancing or transferring torque.Axle is meant for balancing or transferring bending moment.