On the shank end, when I initially cut them, I cut an "M" into it. After folding it in half, I twisted it "M" center upward and forged the shank ends curving downwards. I do not open the shanks back up any more for the rowels, I just cut into the metal with a cutting blade. It saves a ton of time and energy and is about the right width opening for the rowels.
spur end / shank end|discard this end
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4" center cut, 6" to the middle of the rasp or there about. The extra 2" allows for mistakes and creativity on the shank.
On the cut (shank) end, cut an "M"
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Fold it in half lengthwise and open the bands up around a jig to give a good shape for the bands, using the horn/bick by itself is too hard to make it perfect. If you want the bands to curve up with solid buttons, the center cut will have to be 5". Hope this helps, and I hope my diagrams express my explaination.