The Stewmac Ultimate Scraper is a tool worth owning. I have used Lie Nielsen sheet metal scrapers for years, but I think this little jem is going to obsolete those old scrapers. Where do I use scrapers? Binding clean up and wood repairs mostly. Occassionally a patch needs scrapping or leveling. Millwaukee carton blades are much better for small lacquer repair or fill leveling.
The Stewmac sharpening instructions are much too difficult if not impossible for the average to advanced luthier. They suggest buying a mini-grinder and grinding the edge. I say there is a much better way.
The Ultimate Scraper comes with a curved edge and a straight edge. Both edges are hollow ground. I doubt many wood workers or luthiers can achieve a nice smooth straight edge on a grinder using the technique suggested on the Stewmac website.
My approach requires a round burnisher, a 300 grit diamond hone or plate and a 1000 grit plate. You can use a large mill bastard file instead of expensive diamond hone plates. Make no attempt to keep that unnessary hollow ground edge. The trick is to hold the scraper perpendicular to the 300 grit plate or large file and grind off the hollow edges. (The curved edge is not terribly useful, so just cover with electrical tape.) Then use the 1000 grit plate to make a smooth edge.
Once the hollow ground edge is flat, use the burnisher to round over the edge. Light pressure is all you need since it is possible to roll the edge too far. Put the scraper in a vise, Hold the burnisher at 5 degrees to the scraper and rub along the edge. By rolling the edge towards the scraper side you are creating a sharp cutting edge. I cannot imagine why they went to the trouble of grinding a hollow edge when simple burnishing works so well. Gosh folks, this is metal working 101!
Be careful with this scrapper as it can remove a lot of wood or plastic binding in a hurry. And it stays sharp for a long time. Nice! I wish my brain was as sharp. I will continue to use my flexible sheet metal scrapers because those work where a stiff scraper cannot.