Here is the same 1 1/4″ chisel back after about two hours of flattening work. I tried several methods, coarse India oilstone, Shapton 320 grit glasstone and 800 grit waterstone. Progress was made but the amount of hard metal which needed removing was huge, due to the belly created by years of sharpening on a hollow oilstone.
I was reminded of how much I dislike oilstones. The oil migrated up onto the top of the shallow chisel cross section and made a good grip almost impossible. I did not feel that the very coarse waterstone removed metal faster than my favorite 800 grit King Stone, though it was much harder and did wear much less.
The whole sorry, frustrating business reinforces the good advice which I was given during my training. “Avoid bellied chisels like the plague”.
So, as this Pattern Maker’s Long Paring chisel has lots of blade length, I decided to solve the problem by shortening it by 5/8″. This was done in a few minutes with a heavy duty cutting disk in a Dremel. I cut in from both sides and snapped off the offending end when about a third of the blade thickness remained. The good part of the blade is clamped between hardwood pads in a metal working vice. The exposed tip is covered in paper towel to catch flying splinters, and given a good whack with a large hammer.
The Dremel cutting disc worked very well indeed and created remarkably little heat, if used carefully.
This rather drastic remodeling has worked very well and I now have a chisel with a flat or slightly concave back which will sharpen properly. There is still plenty of blade length for another couple of lifetimes.
I wonder if anyone can suggest other solutions for the bellied back syndrome?