"Dave W" wrote in message
...
You've got the blade upside-down! The blade ends should point DOWN.

Yes indeed. With the blade upside down the sharpened edges will not be
the ones hitting the grass.

I'll check the direction of rotation to make sure, but I think it's correct
in that the edge is slightly less sharp that it was when the blade was first
sharpened, and has a small stone chip in it, suggesting that this *is* the
leading edge.

Maybe the blade has got bent the wrong way over the years of usage and (if
it's normal for the tips to bend *towards* the grass) I need to unscrew the
blade, clamp it in a vice and bend the tips the other way slightly.