Emulating manufacturing process

I’m modeling a cook’s knife and I’m stuck trying to reproduce the surface that’s achieved in it’s manufacture. What is seems is that a full length blank is rotated against a grinding surface and results is the surface in the photos. The small arc that is created at the bolster is what remains of a planar surface that’s been ground to a curvature. The problem is how to create a surface that will produce such an arc after it’s sliced.

I’m not sure how to go about reproducing this particular surface. I’ve attached the file. Any suggestions?


CookKnife.3dm (572.1 KB)

knife.3dm (145.3 KB)

I was a bit curious if my suggestion actually is applicable here, so i modelled it fast.
Above you find a 3dm + screenshot.
Now the suggestion:
(Almost) Always build objects they way you would build them in the real world. that way you get the desired effects. If you make a knife - start with a solid block, and start to trim and boolean away parts in the same manner as a metalworker would do it.
In the Rhino file are all the relevant curves - the only solid was a block at the beginning, and several lofted surfaces, but all of them you can rebuild (more or less) easily using the supplied curves.

It is also way faster to work that way - this knife there is done without reference or scale, so it would be slower if there are constraints. It took all in all less than 10 minutes. The trick is really to think in production processes.
Good luck!

Ps. if you take care of proper surface-layouts, you can insert nice smooth fillets to even out the edges. (I think my model was done too fast for that)

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Thanks for the help Atair,

I used a combination of two curve networks to get the edges I needed on the handle. I’ll try to extract some iso curves from the handle and loft a cutting tool, but my attempts before were not satisfactory. Perhaps I’ll start over with a different approach. The tricky part for me was getting the edge of the cutaway for the finger to ease from positional to tangent along the length. I’m not sure how to use cutting surfaces to achieve that.