@Shoki - the formula I provided in this post takes this into account. The larger the angle from the beginning of the cut until the end of the cut, the more slicing will be involved. In the case of a razor, this angle is nearly zero and thus so is the slicing effect.

I believe chefs would take advantage of this formula with certain rotational cutting strokes. For example, a cut with the point of the toe on a cutting board with the food wedged right up to it, followed by a downward motion from the heel could actually generate a significant slicing motion. Think of it this way: as the blade comes down, there would be a tendency for the food to rotate under the knife. Preventing this rotation would induce slicing. I don't really cook, so this is theoretical - but I would bet this a standard cutting technique taught in culinary schools.

@Bruce - "a scything guillotine rotational rectilinear" is priceless. Thanks for the laugh.