Reply To: Convex no. 4 sole — how to flatten?
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Ok, here is what I figured out. It worked pretty well. I think the pictures explain it all, but here it is:
The theory is that a slightly concave sole can be lapped flat, whereas a convex sole cannot. So I created a concave sole from convex, and then lapped as usual. It worked 🙂
I taped 2 guide rails to my granite slab for my #4 to fit in. Then I glued a 3/4″ strip of sandpaper down the middle. This created a concavity down the middle of the sole. Then I used a slightly wider sandpaper strip (about 1-1/8″) to lap that concavity and create a wider one. I repeated once more using a 1-3/4″ strip which gave me the full width concavity I needed (disregarding the 3/16″ or so of worn edge-sole on each side). Finally I lapped normally, giving me the correct wear pattern (wear on the left and the right, increasing toward the middle).
Things I’d do differently: just to use less strokes on the thinner strip. It would have saved time in the final lapping.