I had a similar discussion with 2 good makers not long ago with opposite opinions. I make western knives mostly and am trying to understand the ergos. What advantages are gained from handle at neutral vs angled up vs dropped in the rear? Is there function there or is it style?
See what JMJones wrote below, ideally form and function will both be served by your design.
Finger clearance is determined by the angle of the cutting edge. make a few cardboard cutouts and vary the angle and measure the distance of the heel of the handle. If you make a very extreme angled edge it becomes completely clear.
As mentioned above and from looking at the pics I posted, you can see that handles that are in line or neutral to the spine when the cutting edge heel is slightly angled to it (instead of parallel to the spine) are very slightly raised. This can help give finger clearance from the cutting board while at the same time giving a pleasant visual look because the line is straight from the spine through the handle. Look at the very first knife, the Itsuo Doi and notice the handle install was at a slight angle upwards, and that's why it looks a little off compared to many of the other knives. Depending on use, sometimes knives that have the handle slightly angled downwards can be useful, also some drop towards the butt of the handle aid in your grip in cases, so you may see these carry over into kitchen knives. There are some times when slightly angled upwards can work too tho.
Below is a gyuto where I have the handle in a straight line with the spine with a teeny amount of drop towards the handle butt. I personally feel the straight line between the spine and handle looks better visually than an upswept handle.
Here's a nakiri (sorry for the pic angle, I don't have a better pic) where the spine sloped down towards the front of the blade and I also did a slightly sloping downward handle to counterbalance that a bit visually.
Both were modeled in balsa wood templates first however, and I tested how these models felt in hand and interacted with the cutting board.
I can see how much edge is in contact with the board and finger clearance too:
I can see how high I can raise the knife to rock chop an ingredient under it. A low tip will dig into the board when you try to raise it beyond the limit of the blade belly, so this is about the limit of how high this knife can be rocked.
The last pic also illustrates how handle angle can matter more or less. I tend to use a pinch grip, which makes me a little less sensitive to the handle angle; only my ring finger and pinkie are in contact with the handle and only lightly. On the other hand, in a racket or hammer grip, the handle angle can matter a lot. For a short person who is already low to the cutting board, imagine how they are holding the knife handle when the knife is in the position of the last pic.
Look at this pic of a child using a kitchen knife as an example of a shorter person.
It already looks a little awkward how he's holding the knife (partially because of his grip, but let's ignore that). Now imagine if the handle is angled upwards another 15 degrees how much more awkward that would be for him to hold. Then add in raising the handle up above the food, that's an even worse fit ergonomically.
Now imagine a really tall person who may be reaching down to the level of the kitchen counter. Maybe for them, a slightly angled up knife handle will be more comfortable so they are not stretching down as much? Now if you're not making a knife for a specific customer, then you will probably want to make something that is okay for the average person and their likes/dislikes.
Sorry to be long winded, it's just that I got into knifemaking because I love cooking and was into kitchen knives. So this is all stuff that's what I study and try to improve on when I'm making. Cheers!
