Thread: Using a microscope to define an burr and the edge

Originally Posted by alx

I did a short honing study using a microscope for practice with the scope. The power is about 150x including the camera. The blade is a Yasuki steel kamisori and the majority of the honing was done on the omote side. Some of the final strokes were on the back of the blade on the ura side.

Originally Posted by MykelDR

It seems logical. The more metal taken off on each side, the thinner the bevel becomes at it's most extreme edge. The odd piece is bound to break off.... and not always in a uniform manner. The end result still looks great.

Thanks for posting that remarkable slide show. After reading the original post and informative comments several times I would explain the "breakdown" or "burring" as follows.

After the bevel is completely formed to an apex the steel at the extreme edge is thin enough to break or flake due to the honing forces. When the groove pattern is coarse, micro-flaking occurs randomly in time and at numerous, scattered locations along the edge. As the groove pattern becomes finer the edge variations are less. So when failure occurs, it is more likely to occur simultaneously to a contiguous swath. Thus, we begin to see fractures forming along continuous lines parallel to the edge. This helps explain why edges become more linear as polish and sharpness increase.

In this case the flaking is probably initiated by the alternating front and back honing as you surmised and by the number of reps which caused fatigue to the thinnest portions of the edge. So I wonder if this observed process is typical of most honing sessions or is it unique to this one experiment because of the large number of reps or the fact that much of initial honing was on one side only?