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A smiling edge will help you remove less of the whole edge and give the razor a more pleasing profile.
… Generally the toe and the heel should be the same width, but you can fudge it a bit and it will still look good, by not removing as much from the toe and just accentuate the toe tip a bit more, by rounding to give the allusion of symmetry with a smile.
Note the curve of the toe and heel are the same but more steel is removed from the heel because of the chip….
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