Jan,
Sometimes I like to know the differance between two type of steels in edges. To compare them, my way, is to use
To be able to compare them, those edges must be exactly the same down to, at least, 1/100 part of 1 degree.
That was one of my reasons why I built precission down to this levell. I also enjoy to be able to choose what I shall do to a edge. When I am out in the Forest I sharpen by hand, am I home I use a tool, when I use my tools I can choose what tool and the levell of presision. From all those things I am learning new things.
For example, Fallkniven F1 is a nice knife and I carry it sins some years back as a daily knife around the house. F1 have a convex edge as you know, the convex sphere is 6 degrees. Close to the handle the cutting edge hold 20 degrees per side, 40 degree total. On the belly and the tip the edge holds 13,5 degrees, 27 degrees total. So, the degrees on the cutting egde changes from 40 to 27 degrees along the edge.
The edge holds high angle where people use the highest force - and the edge holds lower degrees where people use less force.
Bark River also use convex edges on their knifes, but there edges are slightly convex, the convex sphere holds 2-3 degrees, that is half of what Fallkniven edges have...
So, both are nice knifes - but their edges work very differently.
You and I can communicate flat edges. We can sharpen the same knife in for example 30 degrees and then discuss how this knife work. But, we cannot communicate convex edges becouse we cannot meassure them (and we have no words for it eather).
My solution with a bended, or angled, guide rod opens up this communication. We can use our Chef
and make identical edges - and evaluate them - and discuss what we have learn from use.
That was one of my demands when I started to create sharpening tools. Also my first sharpening tool had a bended guide rod and could make convex edges.
Thomas
I put off buying one for a long time. After I got the PT50B, the first time I used it I understood what I had been missing.
