Quote Originally Posted by tonyfoale View Post
This is a genuine question not a criticism.
Why are disc sanders popular? I have always failed to see any benefit over a belt sander. The surface speed varies over the face whereas it is constant with a belt.
I have a combined belt and disc sander but I have removed the disc because I could not find any application which the belt did not do better.

What am I missing?
You cannot beat a nice portable belt sander if you need a nice flat or simple convex curve. A stationary is very nice also. I wish I had one, but I clamp my portable in the vise if I must have the belt stationary.

Disk sanders are cheaper and can be made easily from a drill if you do not have a dedicated one. Just today, I made one from a nut, bolt, sandpaper, and a piece of wood. Chucked the bolt in my lathe, got the job done even though the belt broke on my belt sander.

You can get disk sanders (portable) into places you cannot get a belt. A disk is more suited to surfaces that are more complex. Autobody work for example. Yes they have straight line flat air tools in the body shop, but mostly you see orbital disks for finish work or course disk grinders for stripping paint, etc from complex shapes.

I think it boils down to cost, disks are cheaper. On your stationary, do your roughing on the disk, save the belt for those things that need the better finish surface


Lots more examples, but I am being summoned for dinner.