I agree with the above comments. I think it would work, but would require some learning curve, it is probably not worth it and may be counter productive. I see convex sharpening as both sharpening with fine grit sand paper and also stroping on leather when done. I do most of mine on a belt grinder but when convexing on by hand, on the bench or in the field, I lay paper on a leather strop since ultimately I'm going to use the strop to finish up. In other words I don't use a mouse pad.
Wouldn't it effectively be the same as building a mouse pad "block" for you paper and doing it by hand? Just flipping the whole idea upside-down.
Yes, but it adds some more problems. Maybe more then it solves or it's worth.
I think, after you got it all set up, you would have a tendency to press too hard with the EP compounding the problems mentioned. Some of the complications I see are:
- It is easy to apply a lot of pressure with the EP as you are holding on to a handle, standing above the machine, pressing down, have your whole are and body weight above the stone, will tend to use some if it if not careful, etc. It is hard not to apply that pressure. When finishing on a stone especially the finer ones I cradle the arm and hold some pressure off the stone to reduce the weight of the arm.
- With a 1" wide strip of leather or mouse pad you need less pressure then with a wider piece because it will compress and contour (concave) easier.
- Inconvenience - too much set up time and trouble to make the plate (you'll need one for each grit of paper + the bare strop since you will have to glue them on), get the EP out and set it up each time, experiment with angles and pressure each time, etc. Note: You don't have to glue the sand paper on teh mouse pad or strop for free hand convex sharpening.
- With a free hand strop you can check the angle and pressure by moving into the leather just enough to tell it where it is grabbing (leading edge), near the edge of the strop, finding the angle and pressure where you are just contacting the blade edge. This is where the edge will just start to cut into the strop. Granted, I don't do this with sandpaper, but with the paper I can hear and feel the proper angle and pressure free hand. I think you would loose this feedback when using an EP. You could still use the Sharpie trick, but I think it would add steps and free hand convex is already the easiest free hand to execute. One of the nice things about a mouse pad or strop and a sheet of wet or dry is the convenience, light weight, and small storage/packing requirement (like a small piece of leather on a short piece of paint stick and a sheet or two of sand paper).
If you try it I would suggest using leather or a harder mouse pad to try and get less compression of the material.
All that said, I suggest you "Go for it". I think you would learn a lot about sharpening in general, convexing and the EP. Like any new technique, just try it on a junk knife first. I don't think it would be worth the effort either, but I would also like to here the results if you try it.
Are you already convex sharpening free hand right now?
Gary
