Hey Braveheart,
I have done a 25 cm (10″) carving knife with no problem. Here are my lessons learned:
- Hold the tip with my hand when starting out with 100 diamonds and scrubbing hard to do the re-profile (or maybe I use too much pressure)
- May need 2 or passes with each side. I.e – right stone down back half of blade, left stone down back half of blade, right stone down front half, left down front half. Since the stone may not be long enough to get 10″ in one pass.
- When I use the 2 or 3 pass technique above I try to mix up where each pass ends, so that the entire edge is blended. If I was doing 2 passes I would split the blade 50/50 one time, then next stroke to 40/60, then 60/40, back to 50/50 and so on.
My knife was pretty easy, a Henkels 10″ slicer. The edge is very straight the entire length of the knife and the tip has very little belly or curve. So I clamped it right in the middle. If you have more curve at the tip you may have to adjust the setup more to find the sweet spot.
Otherwise I just sharpened it like any other knife. Checked my setup with a sharpie marker, used even lighter pressure since this blade was so flexible, made sure I had a bur along along the entire length.