Lerman,
This looks like it was a loaded question?
Asking why you need one while you were building one, Huh?:biggrin:
There are many uses, but other makers have made great knives without one too.
Your old motor looks like something out of Frankenstein, I love those old beasts and have a few in my shop.
Laurence
www.rhinoknives.com
The Neilsen Interchangable Disk System, like Fred shows has the advantage to have as many flat disks and/or beveled disks as you want or need but need only buy one machine. Check out the system on my web-site and call or e-mail if you need more information.