I wondered for quite a long time about how to sharpen gouges on my Delta disc machine. Finally, it occurred to me that you just need one point support. This geometry works. If you want a fingernail gouge, the contact point would be below the center of the gouge handle. This is super easy and it works. If you want a 30 degree bevel, the contact point should be above the plane of the disc by 1/2 the tool length. This method will work for mylar honing abrasives on glass. You move the tool sideways while keeping the contact point.
The contact point at the handle end is just a dimple in the wood, like this:
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