06:07 Jul 18, 2011 

Thank you. Now I have some more ammo in the ongoing word struggle.
/Björn

16:54 Jul 14, 2011 

@Björn: More context would definitely help. (location of the object, any wheels or pulleys attached, is it part of a drive train or a driven component, etc.)

@Tony: "Spindle" is not really that archaic. e.g. CDs / DVDs are sold in bulk packs called "spindles" or "media spindles" (cylindrical cases containing - with a central supporting rod containing 50 / 100 disks)

15:23 Jul 14, 2011 

In general an axle experiences lateral forces (tending to bend it) on top of the torque it transmits - whereas a shaft or a spindle transmits only or mostly torque

15:13 Jul 14, 2011 

It is quite impossible to give a definitive answer without knowing the context in which is is used, as no single word will fit in all instances.

Generally speaking, an axle may be a component around which other things rotate — in a simple system, a wheel may rotate on an axle; but you can also have a situation where the wheels are fixed to the axle, and the whole thing rotates together.

Generally, a shaft might be considered to be an element that conveys motive power in a rotational sense (though it can also be a longitudinal sense) — cf the 'propellor shaft' in a boat (this could not be called an axle).

Note that cars have axles, but they alsu have half-shafts (which may be called stub axles!)

Remember too 'spindle', which tends to emhasize the thinness of the component, and is also found in many now archaic contexts, like the spindle on a spinning wheel, for example.