The thinnest angle I have put on a knife to date is about 8-10 per side. I have this angle on a Busse Basic and on a small utility blade by Mel Sorg. My Phil Wilson light use knife is at about 15 per side and is overdurable for the work it does so I will cut it down to under 10 next time I have to sharpen it beyond a steel or ceramic rod.
As for how low I would consider, for the better steels I think you can just keep the primary grind which limits it to the 3-5 range for the 1/8" fully flat ground blades. As you approach this by lowering the edge bevel its width will start to rise rapidly, once it gets beyond a certain limit it is best to profile the primary grind down. This radically of course changes the blades design.
I should clarify that at this level it does not take much to break a piece out of the blade. Whittling wood, cutting rope, etc., will not do it, however a hard impact off of hardened steel or rock (carpet) or heavy bone could easily take a large piece out of the edge. As the edge angle drops the durability falls away quickly. These are not knives that you would lend out to people during camping or whatever.
As for thick blades, even my heavy choppers don't go beyond the 15-20 degree range. If it was necessary to do this because the steel was too weak then I would junk the blade and get one it a better steel. The difference in cutting ability between a 30 degree edge bevel and a 20 degree one are huge. On other peoples blades I have gone above 90 degrees (included). These were on kitchen knives that were very roughly used and the edge used to get visibly dented so I had to reinforce it.
However in regards to axes it might easily be necessary to have the edge bevels be far more obtuse than what I find functional on bowies and machetes. It depends on both the hardness of the wood you are going to cut as well as the force that you use. Even when cutting soft woods like Pine, axes are sharpened much more obtuse than 15 degrees because of the possibility of hitting a knot especially on a twist or glancing blow which will impact the edge on a flat and could bow out the blade if too thinned out.
For the cheap axes I will grind them over thin and don't really care about damage. When and if it happens you just grind it out. However if you are in the $250-500 range, you are usually not going to have this attitude and will want to have the level of durability high enough so that the axe doesn't take any damage. Of course this class of axes are usually handmade so discuss the issue with the axemaker who should be able to tell you how thick the profile should be ground to so as to give you just the necessary level of durability.
As for puukos, I have only seen about a half dozen and the grind was about 8-12 degrees.
-Cliff
[This message has been edited by Cliff Stamp (edited 11-04-2000).]
