Theories of Sharpening
Angle Change on Guided Sharpeners
One area that causes some confusion, is how the angle changes on a guided sharpener on the Wicked Edge. Many believe that as the stone moves along the blade, especially along the "straight" portion, the angle changes. This Wiki page documents that this is not the case.
Clay has written a page on how the angle changes (or doesn't) as you sharpen. In it, he describes and shows in pictures how the angle does not change as you move down the straight portion of the blade:
Anthony Yan (Lagrangian) has written an excellent post detailing this. Here's a Summary:
Very often, I encounter people who mistakenly think that a guided-rod set-up cannot sharpen a perfect V-edge. This subject of constant knife angles and pivoting-rod sharpeners always seems to come up, and there are tons of misconceptions. So I wrote this explanation for another forum, but I thought it would be of interest here. Eventhough, I'm sure that at some level or other, all WEPS fans/users already understand the material here, either intuitively, or mathematically.
Below, we will consider two cases: a knife with a circular belly, and a knife with a perfect straight edge. We will show that for these two cases, a guided-rod sharpener that pivots at a point (ie: a spherical rod-end or ball-and-socket joint), will sharpen a perfect V-edge. I won't discuss the circular case for very long; most misconceptions are for when the knife edge is a straight line. However, for edges which are not circular nor straight lines, a pivoting-rod sharpener may not sharpen a perfect V-edge.