At work we have a CNC router table, so a few years ago I laid out some wedges about 4" long in various angles from 10 degrees to 25 and cut them out of MDF. For a short time I was using them as a guide on a dry stone, but I found they were awkward so I only used them as a double check every now and then. I never tried them on a waterstone or a stone with anything liquid on top because the MDF would swell and deform as it absorbed the liquid.
Fast forward a couple of years and I've since figured out that the edge angle is NOT measured from the side of the blade. It's measured from the center line of the blade. So my wedges are all off by between 1 to 4 degrees (per side) because of the thickness (included angle) of the blade itself. I.E, if the blade body is 6 degrees total, then the angle from center to outside body is 3 degrees and therefore my wedges are off by 3 degrees on *that* blade. Make sense?
If I was going to do it again, I'd cut them in 1 degree increments to try to compensate for the above effect. I'd also cut them out of delrin or some other thick plastic so they'd be water proof. Finally, I'd want to rig up something that held the wedge in place at the end of the stone so it wouldn't move or fall over. Maybe a two piece design where a base rests or clamps to the stone and then the wedge fits into a slot making it parallel with the stone surface. But that all sounds like too much work!
Have you considered building an adjustable sharpening wedge to rest your stones on? I build one of those too using this youtube video as inspiration:
[video=youtube;qeWmD5ATBKE]https://www.youtube.com/watch?v=qeWmD5ATBKE[/video]
Mine has a trough cut into the bottom part where a piece of wood slides and has a vertical piece attached to it that does the wedging action. That eliminates the need for the metal rods and stand offs he used. I've used mine on maybe 3 blades. I liked how repeatable it was, but eventually I decided I didn't like it. The sight picture from left to right (sides of the blade) was never the same for me and I ended up making asymmetrical bevels. It also just wasn't as fun as freehand sharpening as I felt like I had to concentrate too hard on keeping the very base of the blade perfectly horizontal through the whole stroke, which is surprisingly intricate with a curved blade. It's a motion in 3 dimensions *with* a turning action also!
I don't think I answered your question exactly, but perhaps I gave you some ideas.
Brian.
