OwenM:
<font face="Verdana, Arial" size="2">Does a high grind that allows you to make a cut with less effort (and therefore less pressure) aid edge retention, since you're not having to force the blade through the material being cut?</font>
Yes, or looked at another way, it reduces the amount of work you have to do to achive a set goal. For example, slice through a rope with a 15 degree bevel and with a 25 degree bevel, both using the same amount of force, the amount of edge that needs to be used (in length) is much greater for the 25 degree bevel.
<font face="Verdana, Arial" size="2">If a thinner edge cuts better, and with less effort than a thicker edge, does this somewhat offset the added strength of a thicker edge bevel?</font>
Exactly. I have been thinning out all my edges gradually and now am down to under 15 degrees on everything including the heavy wood choppers, most everything else is under 10. I have not seen a rapid degrease in edge holding, nor have I heard any such comments from the people I loan my blades out to.
I have been meaning to quantify this in some decent manner but the amount of mundane work it would involve (grinding at least four successive bevels on a blade 25,20,15,10 and doing some work and comparing the edge retention), puts me off. I don't mind the cutting and such, but reprofiling is a pain. As well since all my blades are really thin edged, I would have to go the other way and then grind them back again, a large waste of steel. I'll probably do it on the next blade I get with a thick edge.
It should be noted that in some materials, the geometry of the edge bevel is not completely the deciding factor in the cutting ability. If the primary bevel is also a major factor then thinning out the edge bevel will not have as dramatic an effect on the cutting ability and thus you don't get the offset you described. All you have achieved is to weaken the edge excessivly and the blade now dulls quickly.
You can't ignore this effect in any material however and it determines basically the optimum "thinness" you can achive without losing too much edge retention. It is kind of a critical point, so once you thin the edge past it, the primary grind becomes a major factor in setting the cutting ability, and now you start to lose edge retention.
To again restate one of the more critical points Joe made, becuase M2 is much more durable than ATS-34 (and yes, I include Bos work, I have used 3 examples of it), you can either keep it at the same profile as ATS-34 and use it over a wider range of tasks (rougher work), or thin it out to the desired durabiliry level and get a better cutting knife. Either way the M2 blade will be a better tool - except of course if corrosion is a significant factor.
-Cliff
[This message has been edited by Cliff Stamp (edited 03-14-2001).]