As I said above, sharpening a curved blade is different than a more straight blade.
Blades that have thicker spines present another challenge. You've really got to understand the geometry of your blade in order to understand how to sharpen it.
With a blade that has thin stock (a spine that is not overly thick), curves don't change things much. But once you get a thick blade, curves tend to not be sharpened at the same angle as the rest of the blade. So, when you try to use a constant angle device, like a SharpMaker, you find that you are not hitting the whole edge consistently. This is the "fault" of the maker and the sharpening process that they employ.
I'll give you a real world, easy to see example: Old Hickory butcher knives. I have a 7" Old Hickory that came kinda sharp from the factory. Very usable, if not all that sharp. Looking at the edge, the bevel width is nearly constant from the handle of the blade, up the straight part, and through the curve, and then to the tip. Seems straight forward right?
But when you try to sharpen it, using a constant angle system, what you find is, you end up grinding the last part of the curve, near the tip, much more than the rest. ...and the bevel gets wider and wider as you approach the tip. What's going on? Am I screwing up my blade??? Oh no!
The answer is simple geometry. The Old Hickory is sharpened by hand and the curve and especially the tip portion are sharpened to a higher angle. This keeps the bevel width constant, which *looks* nice. But it's not necessarily good for cutting performance. If you actually sharpen the Old Hickory at a constant angle, you end up with a wide tip. But a very sharp tip! Why is it wide? Because the tip is near the spine. The spine is thicker than the stock that is near the edge. Therefore, the edge bevel is wider. It's just triangle math. Make one side of the triangle longer (the spine or thickness of the blade) and the other side gets longer too (the edge bevel).
When sharpening unusually shaped blades, blades with thick spines, etc, you need to understand these geometries and decide what to do. Will you sharpen at a constant angle and make it nice and sharp, even if it looks a little "funny"? This will require lots more grinding. Or will you increase the edge angle in the areas that need it, in order to preserve the bevel width and it's look? This requires less grinding and will make a blade that is less good at cutting. Thicker edges cut worse than thinner edges.
So, the SharpMaker isn't the problem. It's a symptom. Also the SharpMaker isn't any good at large grinding jobs. For that the DMTs are far superior. As are most other good bench stones.
You should keep the SharpMaker. It's a superior sharpening tool with a specific purpose. It's just not *the* sharpening tool for every job.
Brian.
