There are several ways to sharpen scrapers, (card/cabinet) below are a few sites that can help, #1 is excellent for using a machine, #5 is excellent for sharpening a scraper by hand, all are very helpful :
- http://www.youtube.com/watch?v=VzAYZ92z5C4
- http://www.woodworking-magazine.com/blog/Fourteen+15+Ways+To+Sharpen+A+Scraper.aspx
- http://www.popularwoodworking.com/articledisplay?id=14549
- http://www.woodworking.org/WC/Channels/scraper.html
- http://www.joewoodworker.com/scraper.htm