A belt sander is great for when you are working with wood. Its slow belt speed keeps heat from burning or glazing over the grain. Sanding with the belt sander is done by pressing the material against the belt that rides along a rigid backing platen. While in use, you will be able to feel the seam of the belt thump around and the drag of the belt robbing power. Naturally, less pressure is given to the belt with wood and hence, making the belt tracking system not robust.
If you are looking to do some serious work, then you should consider using the belt grinder. Their belt speeds are usually around 4,000 – 8,000 speed per minute, and this results in a rapid material removal. They are also designed to use either the rigid backing platen or the rubberized contact wheel grinding surface. The rubberized contact wheel grinding provides you with a very smooth feel and an even quicker material removal. The big brand name makers of this tool are: Grit, Multitool, and Burr King.
Their high speed belt action enables most of the heat leave with the grinding chips and dust, and, also, it keeps the belt cool as it spins through the air. But the thing about the belt grinder is that it needs some serious HP and a good robust tracking system that would help handle the high pressure that is usually placed against it. And its belt construction is usually a composition of Zirconia or ceramic material on a heavy backing that is able to handle all the tough work of removing steel.
Some manufacturers – maybe on purpose, or maybe not – usually blur the lines between the meanings and differences between these two tools. What they would do is, in their product description, they would use both the terms sander and grinder loosely. Anyway, what you, as the buyer need to do is to make sure that you select the right machine with adequate power, speed, and durable quality so you can get your job done, and get it done right. You have lots of options to choose from, all you need to do is choose wisely, choose the one that will best suit your needs, and choose according to what has being described above.