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?

Very interesting thread, thanks for posting.

My question is about these microchips and flakes. When a blade is honed to a very very fine edge can the microchips break off on or into your skin? Overhoned? Depends on the metal too I guess, how strong is it. If yes then I would say too fine of an edge is not good for you. If not then never mind.

Thanks all.

Originally Posted by Zorro

Very interesting thread, thanks for posting.

My question is about these microchips and flakes. When a blade is honed to a very very fine edge can the microchips break off on or into your skin? Overhoned? Depends on the metal too I guess, how strong is it. If yes then I would say too fine of an edge is not good for you. If not then never mind.

Thanks all.

in reality what happens is this.
if you overhone the blade you wont be able to get full shave(lets say grown men face)
half face then you will end up stropping again etc.
about the microchips - don't worry about them that is why we have stropping.
hope this helps.

Matt & Bud

I agree with you completely.

Most of my sharpening background is tool based, and although I have shaved off and on for about 40 years with a straight razor my interest in making the slide show was again tool based. My choice of a kamisori razor for the photos was because it is similar in construction to my other laminated bladed japanese tools, those being planes & chisels and the compact size of the razor turned out to be perfect for my microscope set-up.

When sharpening and final honing tool edges, a burr or sometimes called a wire edge can be used as an indicator that the two surfaces of the tools edge are meeting during the process. And in my shop as I progress through the various stones to the final hone my quest is to sharpen through the burr to the target edge, which in theory the burr hides or covers or shields. Knowing the edge is there beyond the burr is sort of like walking through a door to see the next room, until you arrive you cannot see it.

My opinion about the edge includes the idea that the tool steel is damaged to some degree from use or from sharpening. Yes sharpening does damage steel. I feel that a super thin edge like a razor is damaged by a 1k stone, and healed somewhat by a 2k stone and so on. The damage to the edge extends back into the blade from the edge as micro fractures. The steel of the edge may still maintain some integrity and hold together but failure is imminent. For me sharpening is a healing process for the blades edge.

The varied grit particle size found in natural stones be they Coticule, tennen toishi, CF’s, etc. helps to sort of massage an edge to sharpness and thereby healing the edge in a soft way, compared to the manner of synthetics which tend to demand sharpness from a blade by overbearingly sharp and aggressive mono-sized grit particles. A quality natural stone may contain grit particles that fall into ranges similar to a whole host of stones all rolled into one, and each particle comes into play to some degree.

I think that this is why some users of natural stones feel that in using them that they are improving the edge of the razor, not making it sharper necessarily, but improving the quality of the edge in a complex way.

The dramatic event of the burr detaching was a thrill for me but it was in this case promoted and hastened by the addition of an extra piece of tape creating a secondary or micro bevel. In tool sharpening at the highest or finest grits a micro bevel can be obtained by just concentrating on the very edge, sort of like mind over matter, not lifting the blade but just focusing on the edge. Granted the hand pressure coupled with the sheer weight of the blade is greater with tools than with razors. So in effect my burr on the razor was artificially induced. Frankly, micro bevels in tool sharpening is an often debated subject. I favor against them and tend to go for the honing to the Nth degree tactic to just wear through the burr to create a bevel edge that has no micro bevel.

I am thinking that most any honing session that successfully progress to the stage where the 2 sides of the bevel actually meet each other will produce a burr of some sort. In razors it is so small that stropping will remove it without effort. And my hand stropping displayed that to me with a lot less pressure than I normally use on my hanging strop as to how fragile the burr can be on a razor. alx