Brian makes a good point. But to continue it- What you want is enough surface area joined, between the boss and the blade, around the base to spread out the forces and reduce the leverage that the braking forces have on the base's joining. Without seeing the entire boss base joining we can't really say much.

I will say that steel tends to fail slowly with a lot of warning if looked for. I have seen what looked to be far worse boss/blade joinings (welds or brazings) that have been many miles old with no issues. The number of broken bosses (and I don't mean the shaft like in another recent thread here) are very few in real life. Andy