Why does having a point make any difference? Or being blunt? Or inflicting a bruise rather than a cut? It's a knife. I read the OP, he doesn't really want a knife. You think local plod will see a putty knife or chisel sharpened down one side as appropriate for the needs of this bloke?? I don't. It's daft and irresponsible to suggest someone carry a chisel instead of a knife, in view of the original post, and in legal terms.
I realise the OP doesn't want to carry a knife, per se. I was simply making the age old point that has been done to death here many times on BCUK that the general public still perceive knives as weapons instead of tools,
but the alternative use of a putty hacking knife which resembles a regular knife the way a ladle resembles a teaspoon - close, but no cigar, could be an option. Therefore carrying such a less threatening tool,
might curry some favour if the plod do tug the guy and ask why he's carrying such a thing and for what purpose. It's also cheap enough that having it confiscated wouldn't hurt too much. If the copper did want to press the point hopefully wiser minds than his will see the non threatening nature of that tool.
Given the choice I wouldn't carry a chisel in my pocket any more than I'd carry a 6 inch bladed knife
if I didn't have a use for it. At least with a putty hacking knife it looks comical unlike a stiletto. If we really want to get pedantic a heavy stick picked up in the woods could be an offensive weapon in the eyes of anyone who is uninformed, the fact it's a walking staff wouldn't occur to them. Public perception has to be catered for including cops looking for an excuse to tug you. Sad, 21st century, fact.
Comments like mine have been said dozens of times before, and I feel I'm preaching to the choir here. We know what we see and what the public wants to see.
Off my soap box now.