Many years ago when exploring handle materials and design I sat on the kill floor of a local packing plant for four hours. I had a clip bord and had developed a cumulative freequency histogram where I could identify every grip the individual men used. I ended with more hash marks between the grips I had identified. When butchering a beef their hands were all around that handle constantly. I made some grips for different knives that felt good to me and let them guys use them, if they did not like them the knives got tossed out of the way and they went back to their factory stuff. There were no specialists on this kill floor, we all switched places regularly to stress other parts of our bodies while the tired ones rested. If there had been some who did only one butchering task the handles could have been more specific.
Working with sheep horn taught me a lot, as did some work with folks who had developed stressed hands, wrists etc. One had only one finger. With a lot of thought and opportunity I learned a lot of the lessons of the human hand.
Shoe size and hand size are correlated high positive. A man who wears an size 8 EEE shoe will need a long thin handle. If he is thin and does soft work is hand will vary greatly from a man with the same shoe size who does a lot of hard work with his hands.
Using sheep horn taught me a lot about the physiology of the human hand. Crafting a handle out of natural material is a challenge that can be very rewarding.
The best handle shape follows the direction of the hand, (individual muscles) so does shaping the handle. Files and sand paper never go up and down, but flow with hand function. The intended use of the knife also provides a lot of direction. Large deep handles on a heavy duty camp knife stretch the hand out and reduce fatigue.
Every hand is different and it is pretty hard to come up with a handle that fits all hands and function. But: if you do a little thinking and some experimenting you can come up with some very viable alternatives that will work.
When you make a handle, hold the knive and roll it around in your hand, every position should fit like it grew with your hand. As friendly as your dogs head or lovers caress.
The hand is naturally attached to your arm, the knife via the handle should be a natural extension of the arm and hand for the use intended. Droped handles that were made with vision always provide a real learning experience for the knife maker who wants to understand.
We get used to seeing knives a certain way and adapt to them when we use them. For years folks walked past my knives like they had some social disease, then slowly some started picking them up and saying wow! Not every handle fits every hand, but when handle and hand fit it is a beautiful experience.
Years ago a knife maker brought some knives to show me. His first knife was bearing an iron wood handle, a branch. Much of the natural shape of the branch remained as it grew and she was beautiful to hold. He handed it to me saying it was not much. Then he showed me his newer knives. They were well known and popular designs. He wanted to know what he needed to make great knives, I told him that when he needed inspiration he should visit his first knife.
There has been a lot of good thought in this thread and I compliment all who have participated. All makers should make what they like, I do not intend to criticize, but this thread had a following that I hope will understand what I am trying to explain.
Would I make a coffen handled bowie? Not on a bet! But that is just my sentiment. I have been working on one handle for months, it started out as an absolute monstrosity, and is ever so slowly turning out to be great, one stroke with the file at a time. Think about her a lot, then work a few moments trying to get the most out of what one old buck left me to work with. Respect for our handle materials is one essential mark of the artist.
Some will never understand that last statement, but those who do understand know somethng special.