A frequent warning given to beginners peening is to not “overpeen”.
If you hit too hard, too deep into the edge, trying to move too much steel at once, you can open cracks in the steel. You can also end up with a wavy edge, which decreases cutting efficiency as the back of each wave never touches grass.
Lately I’ve been experimenting with deliberate overpeening on thicker blades. I’ve been starting a few mm into the edge and drawing the steel out, but I haven’t been worrying too much about keeping the edge perfectly uniform. Admittedly this started because it’s very hard to do anything but this, on unpeened Günaş blades, because the edges typically aren’t uniform in thickness (we’re told they’re working on improving that right now). So you end up with more steel to move in some sections, which means a broader bevel, which means a wave.
Also, thicker edges naturally require more peening, and more peening gives more opportunity for error. So any inaccuracies you have in technique are effectively amplified by a thick edge; there’s simply more opportunity for you to make more mistakes, so you see more mistakes. This also results in a wavier edge (when you’re peening genuinely freehand).
So rather than obsessing about keeping the edge uniform, I now draw the edge very thin all along the blade – and don’t worry about any waves – with a view to removing the waves with a coarse stone. Having done that, I could peen it again more carefully to get a thin, uniform edge, but instead what I’m doing is to peen thin further back into the bevel in the first instances, so that I can be confident that even after I’ve removed the wavy edge, there will still be thin steel at the edge.
So far it’s worked a treat.