There is a whole number of different sanding devices that are commonly used in woodworking. These include for example the detail sander, the random orbital sander, the palm sander etc. One less talked about type of sanders is the spindle sander (see this article on Woodworkify). In fact, it is a very useful device that every woodworking shop should have. There is a number of ways that this device can be useful to you in your projects. In fact, it can do a few things that other types of sanders will not be able to do at all or will perform poorly at.
One application that immediately comes to mind when talking about the spindle sander, is fixing a curved edge that was previously cut out using a bandsaw or similar. Typically, when sawing, you will not be able to follow your marking line to the millimeter. There will be deviations of the sawpath from the line. As it happens, the spindle sander is the perfect device for fixing such defects. You have to make sure that you use lengthy and smooth motion when trying to fix such deviations and not try to press too hard on a single spot. That would cause unnecessary bumps on the edge.
A spindle sander can also be used to refine and polish a previously cut out edge of a working detail. Again, your motion should be smooth. Do not try to take short jabs at the edge with the spindle because that way you can ruin your working part. Instead do several smooth passes. This will ensure a gradual and smooth and well polished edge.
In fact, a spindle sander can also be used to refine a straight edge that has been previously cut. For this, you should use a wooden plank with a hole that is slightly larger than the diameter of the spindle, and is offset such that the spindle is ever so slightly exposed beyond the plank. That way you can glide the piece that you’re working on along the guiding plank and merely shave off the very surface of it in a smooth manner.
These tasks are significantly more difficult to perform with other machines and significantly slower when done by hand. All in all, this makes the spindle sander an extremely useful device for any woodworking workshop.