Bottom line is that there are so many places where so much has been written on this subject and that ithere are so many variables, that it is hard to give any answer that is definitive…at least for me.
I wrote what I thought was a comprehensive answer, about 6 meaty pragraphs, and once again the forum software ate it. Ijust can’t get up for doing it again.
The reason that I asked about the knife is that the blade steel and hardness is the first thing that I like to know about before even starting to experiment. You di not mention the brand of the knife, so I can’t try to track down what kind of temper aand the resulting hardness that the maker used.
With very hard strong steel you can use smaller angles. Other steels you need to increase the angle to keep the edge strong. ATS-34 can be tempered to yeild from 56 to 59 Rockwell C. Again, knowing exactly what you have can give you a starting place to begin to get the answer to your question.
Personally, if I had a knife with your steel that was 56 Rc I would start around 20 to 22 degrees per side.
At 59 Rc, I might try 18 to 19. Then you see how the edge performs and how the edge itegrity and retention works out and adjust from there. The more acute the angle (smaller) the easier a blade cuts, but that doesn’t do you much good if you have rolling or chipping problems, or if it just gets dull before you finish a job. If the blade will not support the angle, try increasing it to leave more meat behind the edge, or doing a microbevel at a greater angle.
In other words, I am not sure that there is a definitive answer without knowing much more about the knife and exactly what your useage patterns are…even then, it would just be a starting suggestion, not a hard and fast rule.
BTW, you might even be well served by starting off duplicating the factory angles, getting it good and sharp, and working with it for awhile. The maker likely had a good reason to sharpen it the way that he did… even if it was maybe just economics.
Phil
In case anyone wonders about the Rc numbers I quoted, they came from here:
http://www.admiralsteel.com/reference/sstltech.html
Since then I have read that lots of knife makers harden the steel to 59 to 61 Rc.
Still don’t know what Eric has…