I'm just gearing up to do some Veritas bevel up sharpening on the new waterstones using a Veritas mk2 guide for the first time.
It's clear that when sharpening it's (despite most descriptions saying only that it's necessary to create a wire edge) necessary to keep on going until the wear bevels are removed to create the 'V' that comprises a truly sharp edge.
There's a fair degree of consensus to the effect that it makes sense to use three bevels to minimise the amount of material to be removed - the primary/ground bevel, a second sharpening bevel, and a third honed or polished bevel.
This makes sense, but doesn't seem all that practical in the case of the flat side of the blade on a 12deg bed/low angle bevel up plane. Specifically that it's not going to be possible to fit three bevels on the flat side within the available 12 deg, and still be left with enough clearance angle. (which some suggest shouldn't be much less than 10deg anyway)
The fix is presumably to rely on removing the metal almost entirely from the (in this case) top/primary bevel to eliminate both wear bevels, and to only give the flat back enough of a re-polish to remove the resulting wire edge.
Something along the lines of David Charlesworth's ruler trick for polishing the back sounds like it might be a good move - after flattening the back of the blade on say a 1000 grit stone. Provided that is it doesn't leave the blade unsupported over too much distance.
Does this make sense? Has anybody got any experience based angles/thoughts/solutions/methods that work well in this situation that they can describe?
Thanks
ian