I have got three of my old boxwood Marples bevel edged chisels with significant bellies, rather a bow on the full length, 1/4″, 5/8″ and 3/4″. It seems quite impossible to flatten these. I have been trying to flatten them with sand paper on glass, but I don’t think I made any progress with them after hours of lapping. It seems to me that since the bow runs along the full length it is not possible to find an anchoring point so to speak and the bow remains.
I read somewhere that it could be possible to heat them and bend them the other way, although this is not without risk of them braking. In any case, I have no furnace that is able to develop that sort of temperature. I might have to wait till winter to try it at my mother’s fire oven.
Is there anything else I could try? Please give me some suggestion, perhaps there is some lapping technique that can work in this case. Did you have any good experience with flattening bowed chisels?
I have also found a lot of old chisels are bellied. And I also found flattening with sand paper to flat surface can end with a rounded edge. I therefore came with this solution: I grind with coarse paper on a flat surface only the portion that is bellied (not up to the chisel edge), thus purposely creating a hollow. Then when I flatten the chisel back on the stone, it will hit on the edge and at the back.
You want the chisel edge flat enough that you can easily and properly remove the burr on the stone.
That’s my 2 cents if it helps,