Thread: My razor is too sharp???? I like a duller edge??

Originally Posted by mparker762

There is another way of interpreting what you are experiencing.

You get maximum sharpness out of escher after 100 strokes. The edge is as narrow as the escher can get it, but this is the same narrowness as the 4k norton, 8k norton, coticule, nakayama, shapton, etc. But the bevel is as polished as the escher can get it - you have removed all significant irregularities in the bevel from the lower grit hones, and the escher just isn't polishing it any finer. If you wish to get sharper then you need to move to a hone that will leave a finer more smooth bevel on the razor that will lower the effort involved in splitting the whiskers open.

The effect of these two interpretations on the shave is exactly the same - two hones produce different levels of sharpness. The difference is in the explanation. In yours the hone produces sharpness by reducing the size of the bevel to it's minimumlevel, in mine the hone produces sharpness (beyond the 4k point) by improving the level of polish to it's smoothest level.

Since we can't tell the difference between these two theories by shaving, we must turn to another way. Like looking at them under an electron microscope to see if the edge does indeed get thinner as we move to finer grit hones, or if the level of polish does indeed improve as we move to finer grit hones.

When Dr. Verhoeven did this, he found that the edge did not get thinner past about 4k, but the level of polish and consistency of the bevel kept improving past 4k.

Now i am getting whole confused.
will you please explain what you mean by Polishing?
in my opinon BEVEL has nothing do to with sharpness of the blade. Edge does .edge touches to the cutting surface not bevel.
Polishing removes the metal right? as doing so it narrows the edge. makes them come to more close to 'V' shape. and this will increase sharpness.
May be that person was making experiment of chizels axes, knifes etc .
that is different . you don't have to get v edge on them as you know it will get so fragile and useless .

Originally Posted by hi_bud_gl

Now i am getting whole confused.
will you please explain what you mean by Polishing?
in my opinon BEVEL has nothing do to with sharpness of the blade. Edge does .edge touches to the cutting surface not bevel.
Polishing removes the metal right? as doing so it narrows the edge. makes them come to more close to 'V' shape. and this will increase sharpness.
May be that person was making experiment of chizels axes, knifes etc .
that is different . you don't have to get v edge on them as you know it will get so fragile and useless .

We are saying the exact same thing, the difference is in the amount of steel removed after 4k... Some of you think that there is still quite a bit being removed... Myself and others think that there is very very very little being removed...

The > is not getting much thinner after 4k it is getting smoother

Originally Posted by gssixgun

We are saying the exact same thing, the difference is in the amount of steel removed after 4k... Some of you think that there is still quite a bit being removed... Myself and others think that there is very very very little being removed...

That is true. Only, the tools to remove it become also increasingly slower. Hence the need to not switch over too soon. But in the end, you can't paint a fine line with a thick brush.

All in my humblest of opinions, of course.

You did realize I hope, when you started this thread, that we would probably not become one step closer to a unified theory on these matters?

Bart.

Originally Posted by hi_bud_gl

Now i am getting whole confused.
will you please explain what you mean by Polishing?
in my opinon BEVEL has nothing do to with sharpness of the blade. Edge does .edge touches to the cutting surface not bevel.
Polishing removes the metal right? as doing so it narrows the edge. makes them come to more close to 'V' shape. and this will increase sharpness.
May be that person was making experiment of chizels axes, knifes etc .
that is different . you don't have to get v edge on them as you know it will get so fragile and useless .

The edge gets thinner and thinner until it gets to a certain point, then it just crumbles away, and continued honing just removes metal but the edge doesn't get any thinner. This seems to happen at around the 4k mark (obviously this is an approximation because different "grits" are different and act differently - the point is that this happens at a very coarse level, much lower than we would have thought).

Verhoeven looked at commercial razor blades, a straight razor that was honed by an active straight razor shaver, and blades he honed himself using a honing jig and a variety of stones and pastes.

The thickness of the cutting edge of teh gillette blade was the exact same thickness as the edge of the straight razor, which was the same thickness as the edge of the blades he honed using the 4000 grit hone, which was the same thickness as the blades he honed on his 8000 grit hone, which was the same thickness as the blades he honed on 1 micron diamond, which was the same thickness as the blades he honed on 0.5 micron chrome oxide. And the same for blades honed by Alfred Pendray, a noted knifemaker that was assisting him with this study.

The blades were obviously getting sharper, yet the cutting edge wasn't getting thinner. So the question then is what is making them sharper? Because clearly *something* is making them sharper. One thing we can clearly see in his electron micrographs he goes up to finer and finer abrasives is the bevel gets smoother and smoother. But is this significant? What mechanism can we think of that might describe how the bevel's smoothness could improve sharpness?

The commercial razor blade manufacturers have run into this same problem. They needed to improve the sharpness of their blades, but they also need to produce them as cheaply and quickly as possible. Saving even a penny per blade makes them millions of dollars. What they have universally settled on is to stop honing at a pretty coarse level, then bake in some teflon to the edge. This improves sharpness, but how? The blade isn't thinner after this, actually it's a bit thicker. So why is the blade sharper? Because it unquestionably is sharper, at least going by the sensation you get when shaving. So what does it do that we perceive as sharpness?

What the commercial guys claim is that the teflon reduces the friction between the bevel and the whisker as it's being forced open, that the tugging sensation you get from shaving is coming from two different actions: forcing the blade into the fibrin in the whisker, and forcing the two halves of the whisker apart in that 120 micron span after the blade bites into the whisker but before it has come out the other side and the whisker finally floating free in the lather.

This also provides a possible mechanism for how a more polished, smoother bevel could improve the sharpness of the blade. As with the teflon, it reduces the friction between the bevel and whisker as it's being forced open. The commercial guys just find it cheaper and faster to do this by spraying on teflon than painstakingly polishing the bevel.

It's interesting that the knife guys that were testing edge sharpness (before verhoeven showed how to do this with an electron microscope) repeatedly stressed using materials with "minimal wedging and frictional forces", because if what you're trying to measure is the size of the cutting edge then that friction of splitting the material apart is very significant. But for us measuring sharpness by shaving don't have the luxury of choosing our testing material - we're stuck with whiskers which have the tensile strength of copper.

Originally Posted by mparker762

The edge gets thinner and thinner until it gets to a certain point, then it just crumbles away, and continued honing just removes metal but the edge doesn't get any thinner. This seems to happen at around the 4k mark (obviously this is an approximation because different "grits" are different and act differently - the point is that this happens at a very coarse level, much lower than we would have thought).

.

This is True if you are talking about in curtain grit.
Example .
if you use 4 k and edge will get the level 4k can get . after that edge will not longer get sharper if you still using 4k
I agree
But we switch to 8 k and continue to hone edge will get thinner.
This is important understand.

i think what they made experiment was knifes etc.
how they sharpen knifes ? they will never get edge so thin which we get on straight razor.
that knifes edge will broke down after 1 potato cut right?
This is what they doing . they are getting edge on level of 4 k and stop in there . then they start to polishing . by polishing they get a little more sharpness that is it.
i check edge after 4k and 8k and after coticule ,escher.
as i go up edge gets thinner and cuts better .

One thing you have to be careful of with verhoeven's paper is making sure he's doing what we're doing. He does a lot of stuff with tormek machines and various abrasives, and somewhat less with flat hones and leather strops, and the two results are different because of the speed of the tormek machine and the additional angles involved (the razor can't lie flat on the wheel).


Here's two spots where verhoeven talks about this in a relevant context:

Page 23:

"Japanese waterstones in the 6000 to 8000 grit range produced an excellent edge on
these HRC = 60 stainless steel blades with as-ground 2β edge angles of around 40o. The
waterstones produced fairly smooth and quite straight edges as viewed face-on. The
remnant bur width was quite small, on the order of 0.5 microns"


page 24:

"Stropping of the waterstone sharpened blades on a leather strop loaded with chrome oxide compound produced a significant change in the edge geometry of the blades. The abrasive grooves from the waterstone sharpening were smoothed out significantly. The edge bur width was not reduced significantly below the 0.5 micron level of the waterstone ground blades, but it was perhaps a bit more uniform along the edge."


(reading furiously)

Continued:

from bottom of pg 9 - figure 12:

This shows a photo of a 1000 grit edge, taken at 3000x, showing the edge thickness is 1 micron.

He later references this in his flat hone and flatbed strop chapter as being his control blades for that chapter - he takes these and hones them on a variety of hones.

So at 1000 grit the edges are 1 micron thick. At 6000 grit they are at 0.5 micron thick. And at 8000x they are 0.5 micron thick. And at 0.5 micron chrome oxide they are also 0.5 microns thick.

The 0.38 number I was tossing around earlier appears to be the minimum thickness (the edge thickness varies at different places along the edge). But the minimum thickness appeared to be pretty constant. The maximum thicknes varies depending on burrs and such.

Another interesting snippet (pg 11):

"The 600 and 200 grit wheels produced surfaces that were difficult to tell apart. In both cases the face abrasion marks were significantly larger and the edge burrs significantly wider and more convoluted than found with the 1000 grit wheels. In addition, the face view of the edges were significantly rougher and less straight than on the 1000 grit wheels. Nevertheless, the edges produced by the 600 and 200 girt wheels are quite thin, with a burr width on the order of 2 to 3 μm on the 600 wheels and 2 to 4 μm on the 200 wheels. And, from a practical point of view, the edges are quite sharp, being able to cut arm hair as well as the 1000 grit edges. Neither cut hair as easily, however, as a razor blade. This later fact is probably due in large part to the much smaller edge angle of the razor blades, 2β of 17o versus 40o."