What is the difference between a linear motion shaft and a pin shaft? The answer is: The Tolerance.
A linear motion rail is designed to have linear bearings move across the shaft. These rails are usually designed with a tolerance of -15 to -20 microns; enough undersized to accommodate the tolerance of the bearing and allowing it to glide smoothly up and down the shaft. Examples of these shafts are 3D printer machines, manufacturing plant machines, molding machines, etc.
A pin/axle shaft has a tolerance of +10 to +20 microns. A bearing would need to get press fit onto this shaft to fit snug. You can find these sorts of shafts/pins in pretty much most common applications such as roller skates, skateboards, ceiling fans, fans, etc.
Shaft is desired to transfer the motion (rotary), from one member to another, where as the axle is used to support the bearing in rotary motion. For example, if you were to use a linear shaft as an axle, you would find that the bearing would fit loosely around the shaft. The bearing therefore it would be unstable and may cause problems in the application. On the other hand, if an axle shaft were to be used as a linear shaft, you will find that the linear bearings would not glide up and down. The bearings would get stuck. We often get calls from customers with this problem. It is important to distinguish what type of shaft you need according to your application. For any questions, call us, we are happy to help.