Since Iím trying to make these tests as objective as possible, Iíd like to describe my methods in enough detail to allow others to check my results. Below are brief comments with links to more complete descriptions.
After experimenting with different abrasives and testing the sharpness of the edges they produce, I am now honing with ¼ micron diamond paste. The bevel angle is precisely controlled by use of a honing jig, and a small back bevel is used to make sure the cutting edge is formed by the intersection of two finely honed surfaces.
Most of the blades Iím currently using are sharpened with a 31½º angle on the face and a 2½º back bevel. This gives a total included angle of 34º. When a steeper back bevel is used to increase the cutting angle of the plane, the main bevel is left at 31½º resulting in a larger total included angle at the cutting edge. Since higher cutting angles cause more stress on the blade edge, this larger included angle may help prevent edge failure.
Almost all of the planing is being done using a Spiers unhandled smoother with a blade made from CPM 3V. The planeís bed angle of 45º is increased by the bladeís back bevel to produce a cutting angle of 47½º.