All four examples have a cutting edge with a width less than 200nm, although the final bevel angle varies from 21 degrees for the Blue Blade to more than 40 degrees for the Olfa blade. The Olfa blade also has a small burr on the edge which reduces the effective keenness.
At minimum, these examples demonstrate the scale at which we need to resolve and image features is well under one micron.
With our definitions of Keen and Sharp we can see that all blades have similar keenness, but the razor blades are sharper than the scalpel and utility blades. The images below demonstrate that the Feather Super Pro Artist Club blade is much keener than other manufactured blades, but is not nearly as sharp as a conventional straight razor.
21 responses to “A Comparison of Several Manufactured Blades”
I believe your Feather edge measurement data is in error.
You are not measuring the actual final edge bevel.
Please see my post here:
You have opened a large can of worms, my friend. The “actual final edge bevel angle” is ALWAYS 180 degrees.
Through experimentation, I have found that taking the angle between the tangents at about 3 microns from the apex is an excellent measure of the degree of micro-convexity introduced by stropping.
You may wish to read this thread (brush up on your Calculus first)
The Feather Super Pro has a 10 degree bevel with a 19 degree microbevel (these measurements are plus or minus 1 degree).
It does appear that the last micron or so is at a steeper angle than 19° – and it doesn’t look like convexing but a separate tiny bevel. How they are putting that last little bit on the very edge would be interesting to know.
It is not possible to micro-bevel at this scale – this is standard micro-convexity produced by stropping. The uniformity of the apex is also indicative of stropping.
Ah, must be the scale I’m not used to. At that level it sure looks like a tiny microbevel! These blades are likely finished in strip form, right? So they must be doing a power stropping or brushing of some sort. Sure would be interesting to see the factory floor and have access to the processes used.
I was in Japan, so I got my wife to purchase me a case of Feather Super Pro blades off of amazon.jp. I had my first shave with them last night, and it was a great experience. Feels similar to a straight razor using your progression, right after refreshing.
Great work Todd! I have found that on some brands of these blades, they need to be stropped or micro-beveled to get them to cutting well, and it can vary from blade to blade even within brands. Take care!
Love this post, thanks!
Too see the plastic coating in the section makes me wonder how the blade can cut hair.
Perhaps the plastic was deformed.
In the picture with section cut the blade width 3 micron from the apex is doubled with the plastic.
And the apex itself is totally covered in plastic.
How can the blade penetrate and cut hair with this coating?
The thick layer of teflon/polymer is removed with the first use, leaving just a nano-scale thin layer on the steel.
Hi, can I ask how exactly is the cross section image constructed?
I am a little confused by it; does the program simply shift part of the edge downwards or is there an actual physical “cross section” (i.e. cutting the edge across) going on?
The edge is cut and polished with a focused ion beam to show the cross-section geometry.
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Hi and thanks for your work.
Can you describe how you remove the fluorpolymer coating from a feather blade without damaging the blade?
I use gold-coated knife edges for measuring focused x-ray beam cross widths by scanning the knife through the beam. However, I reach the limit of the blades that I use. At the 1µm level the blades are too rough to give good results.
I’m not so much interested in sharpness but rather to have a uniform and straight edge. Ideally the edge variations should be below 100nm on a Millimetre range. From your pictures, the uncoated “Feather Super Pro Artist Club blade” or the “Kai/Miltex disposable scalpel blade” seem to have suitable edges.
Unfortunately, the Kai/Miltex is not a straight knife. That leaves the Feather.
PS: I know of other methods like breaking SI wafers of shadow coating but here would rather focus on knifes.
The bulk of the coating can be removed by simply cutting into a piece of paper or cloth, leaving just a few nm of well adhered molecules. Alternatively, the Feather “carbon steel” blades don’t seem to be coated at all.
If you want something more sophisticated, I can do electron beam lithography patterned gold structures on silicon nitride windows or thin silicon wafers.
Thanks for the tip. I just wondered if the abrasive method would already deteriorate the quality (in terms of homogeneity) of the edge. On the other hand, fluorpolymers are known for their chemical stability.
I did try 400nm Au on sapphire crystal but got mixed results (4µm @64eV at best). Maybe my method (just shadowing as a quick fix) is not good enough to produce fine edges – I need to check that.
A big challenge with shadow masking is thermal expansion causing the mask to move relative to the substrate. Also, you’ll get a cleaner edge by keeping the thickness as low as is usable.
As for removing the coating, cutting a few cm of synthetic cloth (I use cleanroom wipes) won’t have any effect on the steel.
Hello I have a question regarding DE razor blades. I see many of these have names such as Silver, Platinum, Iridium, etc. Many people believe these blades are coated/plated in for example platinum. sounds a bit far fetched to me though. To me it just sounds like a cool name they made up. And platinum would be the highest grade coating, better than gold and silver.
Do you know if any of the blades that are said to have a “platinum coating” actually have a coating that contains any platinum? Can you test this?
I did look at an Astra Platinum and there was no detectable quantity. If there was any, it was less than 1nm and I can’t think of any reason why platinum would deposited or how it could done economically on blades that cost pennies each.
Platinum is also a very soft and weak metal so what would be the theoretical intended benefit here? (especially on stainless steel which doesn’t rust)?
so, a straight razor will cut more tha obisidian blades. I think. Steel is harder and soft at same time. Too complex. Thats why steel of good quality are superior to glass blades. They have movement.
I believe some people say it leaves a smoother cutting experience, because it “seals” the scratches from sharpening for a better glide. Seems to be pure myth though.
Damn I just found this post and damn I think I love geeking on science of sharp. Thank you for being very very cool geeks with the toys to take photos so detailed. I am impressed. I thought for a while there I was possibly be unreasonable expecting factory edges to stay sharp if they even were when you got the blade to begin with!