Blade dimensions and observations

[woodfluter]

Way back in October 2009, ShavenMaven introduced a thread about possible differences in DE blade width and how that could affect the "aggressiveness" of certain blades:
http://badgerandblade.com/vb/showthread.php?t=113829

He measured some with a digital micrometer and found differences that correlated with his shaving experience. I read this and entertained some doubts.

In any case, if there were a lot of variation in blade widths, it could create havoc with my photo analysis of razor geometries:
http://badgerandblade.com/vb/showthread.php?t=162987
I did use just one blade for that out of caution, but expected to see similar results with other blades too.

He asked others to measure theirs. But it didn't seem to go anywhere. So I wondered how to do this better, since any measuring tool that has to touch a flexible blade has a high potential of altering the measurement! I decided that optical was best - no impact. But how?

I had a 25 power field microscope with a reticle.
The field was too narrow to take in the entire blade...
but you'd get terrible parallax errors if you could anyway!
So had to compare against something else.

I arbitrarily picked a Plain Jane old Schick blade as a measurement standard.
I placed the blade of interest on top but offset a bit laterally.
I aligned the left side carefully against a uniform plastic blade box.
Then compared the right sides.
If the inspected blade proved to be wider, I put the Schick on top.
Then measured the difference (if any) where they overlapped.

Trickier than it sounds, because you've got to adjust focus and get the subject edges right in the center to prevent parallax.

So, I couldn't help but notice other things about the edges as I went along (yes, there's a nice old thread with microscopic photos but the pictures have mostly vanished). Anyway, here it all is in a chart:



ShavenMaven was happy with his Crystals, but thought maybe the Derby extended farther, and the Shark even more so - based on micrometer measurements. And found them a bit harsher.

Looking at the table, it's the Crystals and Personna Reds that appear to be out of line. These two are suspected to be made in the same Israeli factory by the way - although the Reds are quite mysterious and perhaps greymarket. All the rest of the modern blades clock in at the same width, within the measurement accuracy of 0.05 mm.

Two of the older blades I have are out of line in the other direction. All the rest appear quite uniform. The Herder and Blu Strike, by the way, are the crudest blade edges I've ever seen. The oldest Gillettes are remarkably finely ground. The later Blue and Super Blue, once renowned, seem surprisingly poor in comparison.

Bear in mind that, if there were a 0.05 mm difference in total width, the impact on blade exposure would be on the order of 25 microns. A human hair is around 100 microns, just to put this in a beardly perspective. The observed differences were closer to 50 microns, just where it could start to mean something.

Particularly interesting are the different characteristics of the edges. One of the Gillette three-holes and one of the NEWs I examined appeared to have an extraordinary fine polish to the edge...but then I wondered if that wasn't aftermarket. My dad used to use one of those Twinplex DE stropping machines every morning. So these blades could have got their polish that way. I'll have to look at the rest of my old blades to see if there's variation.

Of the current blades, real differences here.
A fun mind game:
Pretend I've never used any of them and rank them on how I'd expect them to shave, based on appearance of the edges alone. Here's what I'd come up with.

Best whisker shearers
Feather because of the short, nicely executed secondary bevel with very high polish; and Iridium because of the extremely short secondary bevel and fine grind.

Better than average
Astra because of the well-executed single bevel (but losing points because grind is average); and Shark for the nice polish on the tertiary bevel, but losing points for having three in the first place.

Worst whisker whacker
Merkur because it has three bevels and all of them suck.

Mildest
The Israeli blades (blue and red) because they project a bit less from a given razor.

With the rest falling somewhere in a middle ground. Of the above, I haven't got around to the Iridium yet, but have used the rest. The red Israeli Personna for the first time on Monday (it pulled, but I'd come off two weeks of Feathers so will give it more chances).

All the above ignores nice and important stuff like alloys, heat treatment, coatings etc. but it's interesting how visual apprehension aligns with experience. YMMV and all that...

- Bill

[talibeard]

Nice piece of work Bill! I took my share in blade width threads (they pop up every now and then) and the biggest difference was about 0.3 mm, which is about what you got as well. We concluded back then that this might make a difference in a very mild razor with little blade exposure but would probably go unnoticed in a more aggressive shaving tool.

I don't really see how you can rate a blade for having 2 or 3 bevels; it is freefall anyway. One or more bevels are needed depending on how sharp the first one, making the edge, is chosen in order to keep it strong enough.

One thing keeps puzzling me though with all microscopic pictures and such; we only see the bevels and never the actual edge. No matter how well grinded (or how rough) the bevels are, it still doesn't expose what is doing the job. For instance the Merkurs look ugly but they give me fine shaves and are in the middle for me for smoothness. For me they beat the Astra (SP) and are on par with the Sharks. The beautifully grinded Feathers are sharper than those three and for me smoother than the Astra but less so than the Shark. Actually in the same category as the Merkurs.

Anyway, interesting subject but I doubt real conclusions can be made with these kind of observations. But I can never resist to check these kind of threads either!

[DE Shaver]

Excellent work and quite informative. It's good to have a more objective measure instead of the more common subjective anecdotal observations. Both are useful, however, for different reasons. As Talibeard has indicated, no hard conclusions can be made yet.

[woodfluter]

Thanks Tailbeard!
Glad someone who did this in the past took a look.

...the biggest difference was about 0.3 mm, which is about what you got as well.

Actually, biggest I'm finding is 0.1-0.15 mm, and that's only from one plant! All the rest are exactly the same as near as I can determine. I've tried it, am careful but remain extremely doubtful of micrometer measurements - errors will tend toward the short side. But you're surely right, at this scale it won't matter much to most guys in most razors.

I don't really see how you can rate a blade for having 2 or 3 bevels; it is freefall anyway. One or more bevels are needed depending on how sharp the first one, making the edge, is chosen in order to keep it strong enough.

Know what you mean. But I'll make a distinction between edge geometry and sharpness.

The effectiveness of an edge depends on both. For a given blade thickness and total bevel width, approaching the edge with three equal-sized bevels as Merkur does will result in a less acute blade profile. At the other end of the spectrum, a single bevel with a very short secondary bevel or simply buffing to remove the burr will give the most acute edge.

Yes, it affects durability, even for cutting hairs, but that can be partially compensated by steel composition and heat treatment. I sharpen common pocketknives at around 22 degrees per side. I have other folders with high-tech steels that will tolerate 15-18 degrees per side and hold an edge equally well - but cut far better, although both are equally sharp.

It is, of course, easiest and cheapest to use ordinary blade steels and make more bevels, or just a large secondary one. It requires less precision.

One thing keeps puzzling me though with all microscopic pictures and such; we only see the bevels and never the actual edge. No matter how well grinded (or how rough) the bevels are, it still doesn't expose what is doing the job.

Here ya go: Scanning electron micrograph of razor blade edge, seen from the front no less!


It's a challenge with conventional microscopy and optical cameras. Here's a interesting amateur photographic thread on that:
http://www.photomacrography.net/foru...54fa71d3f8fb29

Scanning electron microscopes get around the diffraction issues. Here's a fascinating view of some edges, combined with text explaining that some waterstone-sharpened chisels can in fact be sharper than a commercial DE!
http://books.google.com/books?id=Ctk...page&q&f=false
I like the way they described a beard as "pre-soaked protein".

Now if you want to see a lot of SEM photos and read about the impact of different honing and stropping techniques, this is superb: http://www.bushcraftuk.com/downloads...nifeshexps.pdf

It's interesting to share different reactions to different blades. Horses for courses to be sure, and what works for one won't so well for another. As said, coatings and all that matter too and you can't see them. But it was revealing to compare my experiences with the edge details.

Now I'll have to dig out one of those pristine Gillette blues or thins and see how they perform!

Cheers,
- Bill

[talibeard]

Great pics and links Bill; I think I never needed this much time to get through one single post!

Actually, biggest I'm finding is 0.1-0.15 mm, and that's only from one plant! All the rest are exactly the same as near as I can determine. I've tried it, am careful but remain extremely doubtful of micrometer measurements - errors will tend toward the short side. But you're surely right, at this scale it won't matter much to most guys in most razors.

You come to 0.25 including the out of production models. You are right there is a serious risk in measuring thin materials but blades are not too thin and relatively stiff; I am used to measure even thinner and untreated steels and supposed to do that with an absolute tolerance of 0.01mm. When you take 2 square blocks of about 20mm wide on either side nothing much can go wrong. I don't know the exact numbers anymore but the majority was definitely in the 21.95-22.05 tolerance.

Yes, it affects durability, even for cutting hairs, but that can be partially compensated by steel composition and heat treatment.
..................
As said, coatings and all that matter too and you can't see them.

And there we have indeed our biggest problems; what steel is used and what is its HRC value. I think no company will ever share that sort of information and hardness is not too difficult to find out but steel composition analysis will be rather expensive.

Coatings have a lot of issues; the thicker the layers the more the edge will be rounded as every layer will increase the radius of what was once the edge.And how well are they attached; I have seen interesting pics of coatings on a new blade and the same blade after use and they certainly don't look alike!

I love this sort of curiosity; you never get everything revealed but you just have to try!

Regards,
Harrie

[woodfluter]

Thanks Harrie! Great observations, not much to add except sincere appreciation for your insights.

I will say that there's more to the steels than Rockwell Hardness - toughness and wear resistance are important too. And you're surely right about coatings affecting edges, although I might guess some of those would wear away from the real working edge pretty fast.

Basic point, from an economic and marketing standpoint:

1. Less cost using cheaper steels and more, wider or simpler bevels. Coarser abrasives, or skipping different grades reduces manufacturing time. Can be adequate but less effective from consumer standpoint.

2. More costly to use very acute edge geometry, trickier tolerances for sharpening and honing, more steps with different abrasive grades. But superior shaving experience. Now, durability results from confluence of all that plus the steel quality, and better steels are surely required for this to work at all.

I've come to appreciate Feathers recently. I also understand why others don't. There's so many things going on besides the blade.

Thanks again,
- Bill

[SiBurning]

It's a challenge with conventional microscopy and optical cameras. Here's a interesting amateur photographic thread on that:
http://www.photomacrography.net/foru...54fa71d3f8fb29Cheers,
- Bill

That's a follow up to my Micrsoscope photography thread here on B&B. The question there is mostly how to interpret reflected DIC (differential interference contrast) images, and the limits of optical resolution. Refer to those threads if you're interested in the technical details.

Don't have much to add. I'll be taking more pictures and posting them somewhere on B&B, but I have some technical challenges to resolve.

Any ideas on how to accurately measure bevel angles, or the thickness at the ends of a bevel? This scope and a micrometer can measure a length on the side to 0.5 micron, but can't measure a width at all--the blade would have to stick through the lens, and there's nowhere to put the micrometer.

[jwilock]

I know this thread is old but I just found it and think it is incredibly interesting - largely because there is scientific evidence that Feathers and Iridiums are sharp, and it also explains why so many here complain about Merkurs. Has any more investigation taken place since this first came out on other blades. Perhaps this kind of look at blade edges of other blades people think of as "Iridium replacements", e.g., 7 O'Clock Yellow, GBE, Perma-sharp, Astras, Silver Blues, etc., would help identify which ones have the same kind of edge as Iridiums.

[woodfluter]

I haven't done any more micro-examinations since this, but hope somebody will! When I get time, I might.

One interesting thing is that I hadn't shaved with the Iridiums at this point, and then used them a lot afterward. And my experience fit the expectations from this examination. I'd forgotten all about that until you pointed me back at this.

So far, I think the details of blade edges should give us a pretty good hint about how the shaving experience will be - but probably little about durability.

- Bill

- Bill

[jwilock]

Not sure who else might have the skill or the equipment to do. So here's hoping you will try again. Might help many here settle on their personal Iridium replacement.

[Sir Walter of Mount Royal]

I know this thread is old but I just found it and think it is incredibly interesting - largely because there is scientific evidence that Feathers and Iridiums are sharp, and it also explains why so many here complain about Merkurs. Has any more investigation taken place since this first came out on other blades.

A leading manufacturer of machinery for making razor blades and scalpels as done comparisons between several grinding techniques. In a internal document, they explain how the geometry of the edges affect the shaver's comfort. When key dimensions differ from the nominal sizes of a standard blade, things go bad really quickly. fig19.jpg

[SiBurning]

It's always internal documents. We must remain in the dark.

sigh!

[Viseguy]

Awesome thread! Thanks for resurrecting it. If anyone does more micro photos, I hope that Personna Med Prep and Lab blades will be included in the mix.

[woodfluter]

Just to be clear...I don't and doubtless never will have a scanning electron microscope!
I hope nobody was mislead.
The photo in the post was from one of the articles I cited.

All I used for examining blade edges was a 25x a field microscope - because I have a measuring reticle for that.

If I do this some more and expand/modify the table, I'll use a 25x and 50x stereo microscope for evaluating how fine or coarse the grind is on the different bevels.

- Bill

[Shmu]

Just to be clear...I don't and doubtless never will have a scanning electron microscope!
I hope nobody was mislead.
The photo in the post was from one of the articles I cited.

All I used for examining blade edges was a 25x a field microscope - because I have a measuring reticle for that.

If I do this some more and expand/modify the table, I'll use a 25x and 50x stereo microscope for evaluating how fine or coarse the grind is on the different bevels.

- Bill

PLEASE! I'd really love to hear any new observations you have. The other day I noticed that the ASTRA blade that I was trying seemed to be wider than any of the other blades I've used. I don't have any equipment to do an analysis of this myself so I googled it for a little and now I'm giving this most noble thread a bump.

BUMP!

[mikey]

One thing I have noticed is that Kai DE blades are significantly thicker (and therefore stiffer) than other DE blades.

Thanks,
Mike