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

Originally Posted by hardheart

what about blade 3-63, 0.26 edge width after 1 micron diamond

That was on the tormek machine, and was honed differently from the ones in chapter 4 that were honed on flat hones and flat strops. These blades were also honed at a 40 degree angle while the ones in chapter 4 were honed at 48 degrees, all of which makes it difficult to directly compare the numbers between the two chapters.

Originally Posted by hardheart

interesting that you can't notice improved sharpness on razors during shaving at these levels, it shows up on knives when push cutting newsprint.

I never said that you can't notice improved sharpness past 4k. You can. The question is what causes this - is it because of the reduced edge width, or something else?

I think this is readily noticed in imagery already out there, the edge is further refined past 4K. The scratch pattern on the bevel extends to the straightness of the edge, it is also visible in Verhoeven's micrograph of the 6K edge, and the improvement after the stropping. Some of the pictures I consider less than useful for hand sharpeners, as the appearance of the edge off the Tormek won't be anything similar to what you expect from unpowered hones and strops. There's a reason we use power tools, and the difference in finish on metal or wood after X amount of time from a belt sander and a sanding block with the same grit shows it.

Yeah, I've heard of safety concerns from those who just don't trust a sharp knife, but others talk of a 'working' edge, essentially one that is applied quickly with a coarser grit and provides more slicing aggression (totally useless in this context here). It also comes from the mistaken notion that a sharper or thinner edge will dull faster. The initial cutting ability is lost quickly, but that is true at most finishes, the initial sharpness drops immediately and then plateaus at a certain point (this is a measured result from a few knife tests on abrasive material like Catra, manila rope, and cardboard) Yet, a sharper edge is reduced to a lower level of sharpness, which will still be higher than the edge that started off duller to begin with. And a thinner edge requires less force to make a cut than a thicker edge of equal finish and a greater included angle.

I think you guys work in a tighter range of angles, so this really shouldn't be a concern, but sometimes the edges just fall apart when you go too low. The steel does not have the ductility to withstand sharpening forces when it is made that thin.

It is of course very important to note the difference in sharpening and edge angle of the blade that managed the 0.26 micron edge width, but that is also a commentary on the suitability of certain combinations of honing tools, steel, steel properties (hardness, toughness, wear resistance) and chosen edge angle.

I've been reading about and participating (as a rank amateur) in these sharpening discussions for a few years, but to read about the perspective of a straight shaver is pretty cool. Maybe I'll get there one day.

Originally Posted by hardheart

I think you guys work in a tighter range of angles, so this really shouldn't be a concern, but sometimes the edges just fall apart when you go too low. The steel does not have the ductility to withstand sharpening forces when it is made that thin.

We definitely have that problem. Verhoeven mentions this as well, that dropping from the 40-50 degree angles used in most of the paper down to 17 degrees made it much harder to get a consistent, sharp edge (pg 21 "sharpening a blade with the 2β edge angle of the razor blades, 17o, is more difficult than a blade with the 2β edge angle of 40o"). Some straight razors have very shallow honing angles, as little as 13 degrees (see the Hart razor thread in the Razor forum) and these have trouble with the edge collapsing prematurely.

One thing that really strikes me looking at page 41, table 6 (4 blades honed on 1 micron diamond on the tormek machine) is what a tremendous variation there is between the blades. I don't think we can directly compare these to the chapter 4 blades, but they can be compared with each other. These blades also seem to have been analysed more rigorously than the ones in the rest of the paper.

# min/max avg
3-63 0.18/0.34 0.26
6-63 0.20/0.42 0.31
7-63 0.20/0.38 0.29
8-63 0.34/0.45 0.39

That's a range of 0.18 - 0.45 microns all from identical blades honed on identical 1 micron diamond abrasive. He also mentions doing the same thing with chrome oxide and 6 micron diamond and the edge widths increasing by 0.1 to 0.2 micron for both of them. But that's far less than the 37 micron variation we see here in this one situation. Which makes me wonder just how much any of these numbers really mean; I wonder if the sample size is too small.

Seems to be too many variables, and it would require much more testing to remove them. Quality and consistency of the abrasive, the substrate, the skill of the user, force/speed/consistency of stroke against the wheel, the condition of the steel microstructure, etc.

I wonder how hot the edge got. 90 RPM is pretty slow, but Roman Landes recently gave a demo at Ashokan where he shows that the edge can reach a thousand degrees while sharpening. Diamond (carbon) will break down when working steel (iron + carbon) on some power equipment, I wonder if that is also a potential factor fpr the test.

Without trying to be cute, I am completely out of my league with you guys in this conversation about microns and hones. But, I do believe something is being overlooked for all the focus on the blade: the skin!

I have reasonably sensitive skin. I use a sharp professionally honed blade on it and I have some weepers, and definitely have irritation. If I run the blade over balsa coated with Chromium Oxide 0.3 or 0.5, and even put a little pressure on my stroke, I believe the sharpness of the edge decreases.

Everything I read says that pressure on a strop or balsa, causes the leather or strop to roll over the edge to some degree, rounding the edge. I have to assume by this that the edge is being rounded somewhat. Before, the sharp blade cut hair like crazy. After stropping with Chromium Oxide, it still cuts hair well. But, not as well.

Sharp blade. Sensitive skin. Close shave. Irritation...

Less sharp blade. Sensitive skin. Close shave. Great BBS shave!


Lynn said something in support of sharp. For those on this thread who feel this way, it would be interested to know something about what type skin you are wielding your weapon upon.

I don't think we're overlooking it, we just haven't addressed it directly in this thread, it gets mixed up in things like sharpness or smoothness or whatever.

But there are two things on your face for the blade to cut, whiskers and skin. In a perfect world the edge would cut whiskers easily but not cut skin easily. In an imperfect world these two requests are in opposition to each other, so we must strike a compromise between these two competing request. In my case, the happiest compromise is somewhat less than maximally sharp, which whacks the whiskers nicely yet leaves my skin happy. For others with different whiskers and skin the sharpness that best balances these two demands may well be considerably different. From the discussions on this topic so far, maximally sharp seems to be a common solution, but it is also clear that it is far from being a universal solution.

I wouldn't say that I like a duller edge, I simply prefer one that is finished off at a lower grit.

My edges start passing the HHT at DMT1200, as said by somebody above. That is how I know the bevel is set, and then I refine from there. So, by my definition, the razors are all "sharp" at the 1200 stage.

For a while I have been honing to 8k (DMT EE), then doing some Chromox stropping, and I have been enjoying the shaves. I hone until I get a silent HHT, and minimal glint along the egde looking under a bright light source (I don't always use the scope...)

I recently honed a razor up to 0.3um lapping film-- Weepers, discomfort, dissapointment.

Re-honed that razor to 1.0um lapping film, and the shave was back to ease, comfort, etc, etc...


Way back when I first started, before I even knew anything at all I found the exact same thing: Finished to 0.5um-harsh, finished to 1.0um-nice, finished to 3.0um-not so good. 1.0um seems to be the sweet spot for me.

That was a year and a half ago. I've honed many razors since then, and my technique for shaving has most likely gotten better (I hope!). So, that is why I wanted to re-visit the upper reaches of honedom. I had the same experience again- finishing at too high a grit makes for an uncomfortable shave for me.

I'm hoping to do some more experiments with this while documenting using the scope, time permitting.

Originally Posted by Seraphim

I wouldn't say that I like a duller edge, I simply prefer one that is finished off at a lower grit...

I read your post several times, Seraphim, and I don't think you really spoke to what you think is happening when you "finished off at a lower grit". And, as we have probably demonstrated by this long exchange, everyone here might have difficulty knowing (without powerful micro imaging) what is happening. But, at the minimum some of us prefer a blade not finished to the nth degree of what is commonly referred to as sharpness.