A variable speed lathe makes a great disk sander. You can adjust the speed of the sanding disk to control how fast you remove wood and to avoid burning the end grain on woods like Cherry.
I mad my own 12″ disk sander. For more informatin click on any photo. Each photo has a caption with more info.
Full Disclosure: Anyone who has visited my studio knows that I also have a big 6″ x 89″ belt sander that I use for most things. My students use the disk sander. I probably should use the disk sander more often because I get really frustrated when my high speed belt sand burns woods like cherry.