Here's a good How To. Om Building a 20 inch, BIG Disk Sander, Use and Tips by bongodrummer. Check out the info and Video and Related links below...

Don

BIG Disk Sander: Build, Use and Tips

The disk sander, in its mostly finished form.

I've lost count of the times when I have been mid project and thought, what I really want now is a nice big fat disk sander. With them you can make precise angles in wood and metal. You can produce brilliant outer edge curves, and very accurate circles. You can quickly remove material and flatten off stock that's too small to be safely planed, or thicknessed. You can sharpen tools, tidy up rough edges, deburr and square up, and do extreme toenail manicure (just in case you're insane, I'm not really recommending that last one).

In short, a disk sander is an awesomely useful machine to have in the shop!

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http://www.instructables.com/id/BIG-Disk-Sander-Build-Use-and-Tips/?ALLSTEPS