Draw a very acute angle on paper. That is a single bevel. If it is to be made within the dimensions of a knife blade the edge angle will be very small, indeed.
A little quick math shows that for a blade with the spine .125" and sides of 1.25" the edge is 6 degrees. That will be one heck of a slicer. The problem is that it will chip and wear easily. By adding a tiny secondary angle of, say 12 degrees, the blade is the same thinness, but the edge is tougher.This is good for slicing blades.
If we make the blade so the edge is about .040 wide, and cut the secondary bevel on that, the blade becomes very tough. This is good for chopping and heavy use blades.
There are many types of blades made for extremely delicate slicing that have single bevels, but the predominant edge type is double bevel.
Blade geometry is what sharpness is all about. The steel type and hardness have to do with wear resistance and toughness, but sharpness is purely geometry.
Stacy
