Bowed Bellied Chisels

[owen]

You're worrying about nothing. It just needs the end of the back flattening, say the last inch and then sharpening. Don't get hung up on using straight edges against your chisels there really is no point. Get them sharpened and used.

 

[David Martin]

In my experience it's far too common to spend way too long worrying about flattening chisel backs. Most come from the factory with a concave grind on the back to allow quicker flattening of the areas that matter (i.e. the tip and sides along the length) to give 3 reference points. That said a severely bellied or bent blade will be an issue, but remember you only need flatness where you need a reference point. for many operations the last inch or 2 is all that is required. Keep these chisels for that purpose and get some better ones if you need them for deeper cuts where the flat area needs to be longer.

 

[Argus]

I've come to this one a bit late, though I see that the same question popped up on Paul Sellers' forum.

I've read all the answers and prompted by that checked all my old (pre-war, mostly) forged, bevel-edge Marples and Sorby chisels.

I have bought them all,one at a time and second-hand over many years since the late 70s, mostly from some of old tool shops that have largely gone. Penny-Farthing in Salisbury, Bristol Design, an old tool shop that used to be in Bosham just by the harbour........ the old shop in Colyton etc.

I've used them over that time and sharpened them (mostly by hand) and when I checked them with a straight edge just now, I found that none are flat. A few are convex, most are concave. The thinnest ones, 3/16 to about 5/16 being a bit concave will flex flat quite nicely on the stone. It never occurred to me to do this check before, but they all have a nice mirror-finish on the last inch or so, are sharp and are used regularly.

It is possible that some of the new, engineered chisels have engineering-tolerance-flatness on their backs - can't say, I haven't got any - I prefer my old pre-war stuff. There's good edge-holding steel in them.

We are talking about fractions of a millimeter. I've never considered that a slight 'wonk' in this type of bevel edged chisel has ever compromised my work.
I should add that when I need to pare a flat surface that I cannot reach with a plane, I use a paring chisel, or a float, which I do know is flat because it is made that way.

But it's an interesting question.
Judging by the name stamps, I'm probably the second, third or fourth user of these old Marples'. It probably never bothered them and it doesn't worry me. They might be 70-or-80-odd years old and a bit bent, but they are very good chisels.