I have not tried a belt sander on blades.

There are two alternatives in my shop. One is a 4 foot long hunk of granite on a tall horse with PSA backed 80 grit.

Here is the granite on the horse when it was first set up:

Granite on Horse.jpg

Gee, my shop was much less messy back then.

The other is the Veritas® Mk.ll Power Sharpening System:

http://www.leevalley.com/US/Wood/pag...35&cat=1,43072

Both are great assets for working blade backs and bevels.

jtk