Peening makes the blade thinner, and therefore more prone to damage. Keep that in mind when deciding how and when to peen. As an example, Marshall didn’t peen his 50cm blade for months, preferring a more robust edge for more ‘challenging’ mowing.
Using the jig
The jig needs to be bedded in to a solid base at a good height, so that you can rest your blade on your lap such that the jig is at the right level to take the blade. Drill the hole smaller than the width of the spike to allow it to bed-in with the hammer blows. For the solid base, a sawn off log is adequate, or you can get all fancy-pants with a purpose-built peening bench (which you can potentially interchange between the jig and an anvil).
You can use any hammer, since the jig’s caps are doing the shaping. You don’t need to hit the caps hard, especially with the Falci blades. You can always make another pass if you need to, whereas if you hit the blade too hard you’re likely to crack the edge or make it too thin, both of which require more investment in time to correct.
The pattern you’re aiming for on the edge of the blade is a series of crescents where each strike overlaps the previous one.
You may like to practise using the jig before working on your blade. You can do this with a piece of cardboard or a thin piece of uniform softwood timber – anything that will take a mark from the cap so you can see what you’ve done. Never hit the cap directly onto the anvil of the jig, always have something in between.
Both the caps are marked – the one you should use first has one ring, the one you should use second has two rings. The first shifts metal (which behaves rather like a very viscous fluid) from deeper in from the edge, to closer toward the edge, while the second works right at the edge.
The blade edge needs to be clean and free of rust – carefully sand any rust off to about 5mm back from the edge, on both sides of the blade.
When using the jig, the blade faces up – the same way it faces when mowing. It’s important to hold the blade so that the edge of the blade under the cap is as flat as possible, and so that the edge sits on the jig’s anvil across the width of the jig; keep an eye and an ear out – it’ll start to make an unpleasant ring if you start to lift the edge, and that’s when you’ll start damaging the blade.
Once you’ve peened the edge, you’re likely to have a dull edge from where the blade has run along the post of the jig. So dress it with a fine file or coarser stone to take off any burr or dull edge, before moving on to a finer stone.
Using the anvil
Using an anvil for freehand peening can give you more control and flexibility over what you do to the edge. It also gives you more opportunity to really make a mess of the edge if you’re not reasonably competent swinging a hammer to hit a target. But that said, it’s not rocket science, so if you’re confident enough to drive in nails with a hammer, and are prepared to learn from your mistakes, you may as well get in and have a go – once you’re doing it well, the results are much better than you’ll get with a jig.
The basic principle is the same as the jig – you start deeper in to the edge, work a ‘line’ of steel back toward the edge for the length of the blade, and then start another line, closer to the edge. Typically 3 or 4 lines are peened, with the last one being on the very edge of the blade, with the blow more perpendicular (so that you’re compressing more, rather than deliberately drawing the edge down). With the Falci blades, the bevel is already quite thin, so peening should be performed very carefully and with restraint. As a starting point, try peening just the last ‘line’ – the very edge – and see if this gives you adequate peformance (we find that it does).
You need a clean-faced hammer that is genuinely flat, or very slightly convex (that is, the middle of the face protruding). Put a straight edge over the face of the hammer to check that it’s not actually slightly concave (some flat-looking hammers you’ll find in hardware stores are actually slightly concave – the edge of the face is further out than the middle – which will result in your not hitting the blade where you think you’re going to hit it).
Again, the edge needs to be cleaned, both sides, at least 5mm back from the edge. Our sanding blocks are ideal for this purpose, and have the added advantage of leaving a matte buff on the edge, which, when struck with the hammer, leaves a visible, more shiny point of impact which shows you exactly what you’re doing.
Unlike the jig, with the freehand anvil you strike the back (underside) of the blade.
This series of videos of Phil Batten peening is a very good visual guide.