Razor blades

G

ghost squire

Joined
Feb 1, 2004
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How do they sharpen razor blades? Has anyone taken a tour of the factories?

I'm curious about the angle of bevels various manufacturers use, but more specifically exactly how the hell they put that cursed literal razor edge on their product. I've taken a couple of different brands of razor blades and tested their sharpness, then sharpened them carefully using a 10,000 grit waterstone and 0.3 micron abrasive paper. I can never get that razor sharpness though, it comes in about as sharp as I can get a regular knife, 75 grams, versus what it starts out with, ~30 grams, give or take 15 grams. What am I doing wrong, too much pressure, not taking off the burr, not fine enough abrasive (not likely if you read the paragraph below you'll see why), something I'm doing wrong with the stone perhaps?

I looked at it under my Intel Qx5 USB microscope, and the funny thing is I actually get the edges smoother and far more consistent on the Merkur razor then from the factory. Haven't gotten around to looking at a home sharpened Bic yet, when I do maybe I'll host them on photobucket or something for you guys to see.
 
What do you mean when you talk about measuring sharpness in "grams"?

Are you talking about straight razors (the kind with handles) or about straight edge disposables, or about face-shaving plastic-handled disposables?

I, too, have long wondered just how they get millions and millions (probably billions, actually) of tiny razor blades shaving sharp! It's kind of mind-boggling.

-Jeffrey
 
It's not true. Mythbusters tested it. While I do not think everyone should take Mythbuster tests as gospel, their test combined with the fact that there is no good *REASON* a razor should sharpen itself just because it is in a pyramid makes it pretty easy to dismiss the whole idea.

Oh, and Jeffery, I think he means the amount of weight (or downward force) it takes to pushcut something... though he doesn't say what he is push cutting. When comparing sharpness people often say knife A took X amount of force (usually related in grams) to push cut through [something] and knife B took Y amount of force to push cut the same thing.
 
Alvin has tried to obtain the same information several times, with little success. I have fooled lightly with sharpening them in the past, the flexibility makes it fairly difficult. Jeffrey, sharpness measured in grams represents the amount of force necessary to cut something, in this case it is light light thread.

-Cliff
 
Sometimes a bit of a sawtooth can cut better than a perfectly smooth edge.

Also, razor blades tend to be much thinner than knives. The angle is fairly acute as well by comparison.

From what i've researched, razor blades are repeatedly dye stamped at 800-1200 strokes a minute. o.O I'm not sure as to whether they are stropped afterward.
 
Were you starting on a 10,000 grit stone? If so you should try sharpening with a lower grit first. With straight razors you generally start on a 4,000 grit stone and then switch up to an 8,000 grit stone.

I don't think you need to go to 10,000 or finer. I doubt that store bought razor blades are that highly polished. You could probably get them back to like new sharpness with a 600 grit stone.
 
I've read that razor blades aren't actually ground, honed or stropped, the edge is made by some high speed industrial rolling or stamping process. I've never looked at one under a microscope but I think that would be telling.
 
ThreadMoving.jpg
 
Yeah, sorry for not being more clear, I was referring to poly sewing thread that I use to test sharpness. A razor blade takes circa 30 grams to push cut it etc.

Sometimes a bit of a sawtooth can cut better than a perfectly smooth edge.

Also, razor blades tend to be much thinner than knives. The angle is fairly acute as well by comparison.
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Right, but I'm strictly talking about push cutting.

Acuteness of edge doesn't play in as a factor in push cutting something like poly thread, if I'm not mistaken.

Were you starting on a 10,000 grit stone? If so you should try sharpening with a lower grit first. With straight razors you generally start on a 4,000 grit stone and then switch up to an 8,000 grit stone.

I don't think you need to go to 10,000 or finer. I doubt that store bought razor blades are that highly polished. You could probably get them back to like new sharpness with a 600 grit stone.
Click to expand...

I just took a look at a Bic, and it doesn't have scratchmarks. It is also not polished, which puzzled me greatly, until I heard this:

From what i've researched, razor blades are repeatedly dye stamped at 800-1200 strokes a minute. o.O I'm not sure as to whether they are stropped afterward.
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Now I think Inspira and Dog of War are almost certainly correct, I think with modern plastic handled disposables there is no conventional sharpening process.

Now the confusing part, the Merkur double edge safety razor disposables that I tested came in at 30-50 depending on where the blade I tested, as opposed to the Bics which are supremely consistent. Under the microscope I discovered a burr in several places, accounting for the readings above 30. But more significantly they were sharpened with conventional grit abrasives, and Wade is correct in saying that it looked about 600ish grit, with parts of the bevel polished. But they didn't polish the large scratches away.

SO how exactly do they get these Merkurs that sharp using conventional sharpening methods? Our only hope is to contact one of the workers that manufactured them, as these particular razors are about 20 years old I believe. I highly doubt they bother sharpening disposables with abrasives anymore.
 
I think from what I have read about Gillete in an old National Geographic articale on platinum that the process was a rather well kept secret.
 
Allright, I just sharpened one to 30 grams. I think the key is to use very light pressure, I did a few strokes on each side. When you polish the steel with a 10k stone, you can actually see the carbides in it! They reflect shinily. This means the razor was probably stainless, as I'm betting they wouldn't spring for HSS.

To make sure I actually reached the edge and just wasn't getting the sides, I sharpened it at a very high angle once.
 
That is fairly impressive, the sharpest knife I have ever handled was above 40 g, and it was serrated which tends to elevate the thread cutting because the curves will turn the push cuts into a slice. I have not done any high polishes in awhile but generally I am happy going below 100 and rarely get under 75 with consistency.

-Clif
 
100 and rarely get under 75 with consistency.
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Same here! My theory is that we shouldn't feel bad about it though because its a limitation of the steel we are sharpening. I have serious doubts about an Opinels ability to take an edge sharper then that. I'm guessing that 40g serrated knife was a Spyderco :)

PS to be more clear, I didn't see the carbides with the bare eye LOL... I could just barely see them at 200x. I know you know that, just for other people.
New Bic:
newbic.jpg


Bic sharpened by me on a 10,000 grit stone:
bicSBMset3testedat30gramssharpeneda.jpg


It now appears that the razors are indeed at least primarly shaped with abrasives, however who knows how that last bevel is formed. My bet is still on stamping.
 
Yes, Spyderco dominates the sharpest knives I have seen by a strong margin. I have been doing a lot of x-coarse sharpening lately, mainly for cardboad cutting, plus I wanted to check limits. I get about 100 g on x-coarse edges now so I think I can get better than I used to on the x-fine stones. It is all just a matter of what you have seen and what you are willing to accept as sharp. The more of it you do and the better you see, the higher you tend to want. Right now I can sharpening even AUS-4A, a fairly low end steel by most margins, and after cutting over 40 meters of it on a slice through 3 cm of edge, still cut newsprint on a push at a 45 degree angle. This kind of edge retention is only possible with a high initial sharpness and the optimal edge angle. In this case it is decently low, ~15 included. Those kinds of steels are hard to get really sharp though, magnification helps a lot. A few years back I probably would have settled for that sharp initially off the stone.

-Cliff
 
Wondering if anyone's ever done any quantitative measuring of sharpness of a Wyoming Knife? I believe the replaceable blades are made by one of the big razor blade manufacturers:

http://www.wyomingknife.com/knives.htm

Years ago my brother, wearing a large, fresh Band-Aid on his thumb, handed me one, warned me it was very sharp .... and damned if the gutting edge didn't just absolutely melt right into my index finger. Weight of the die cast handle probably had something to do with it, but it's the only blade that ever really intimidated me.

Getting curious now so I'm going to email them and ask if they can't tell us more about the way these blades are made. Let you know what they say.
 
From what I have seen it is a matter of a few factors, mainly not doing enough work on the coarse hones shaping the edge, this is the main problem, the edge should be sharp at every stage of the hone, if it isn't then you are just leaving much more work with the finer hones, even extremely coarse edges can shave, push neswprint, etc. .

Other problems are lack of angle control, which can mean it takes 10-100 passes to do the same as one if you can be consistent with a jig or just experience, this leads to frustration, incompletion, more force which causes problems of its own, and the list goes on. Another critical issue is not using high angle cuts to remove the burr. Goddard and Clark are two of the few I saw who noted the burr removal has to be *really* high, meaning often double or triple the honing angle, they are slightly different in finishing, Goddard leaves the high strokes, Clark removes them.

This is why when people say they don't want coarse edges to shave they are really missing out, all this means is the edge is not aligned, burred, contaminated or impacted. How can you argue this is a superior edge, it doesn't cut as well, is more fragile and has worse edge retention.

Sharpening essentially consists of two steps, shaping an edge until the bevels meet and then removing the burr, a very simple goal. The problem is steel is very flexible so it can just deform and can also chip under the abrasive, plus the abrasive also fractures which is a contaminant. Diamond hones remove some of the problems, used dry though they create others as the high friction tends to charge the particles and then there is static "gluing" of debris to the edge.

I have tested various utility blades, they are decently sharp, but several knife makers/manufacturers can make blades which are consistantly as sharp or sharper. Spyderco for example can get better sharpness than Olfa does on thier blades. Dozier's are fairly impressive because of the level of push cutting sharpness he achieves while having a *really* coarse finish.

R. J. Martin is also supposed to have a very high level of initial sharpness I have not used any of his knives, Murray Carter is as well. I have used one of Carters and it wasn't very sharp, no where near a decent Spyderco, but you have no idea how many hands a custom passes through before you buy it, plus the edge could have degraded from corrosion, etc. .

-Cliff
 
Cliff Stamp said:
Sharpening essentially consists of two steps, shaping an edge until the bevels meet and then removing the burr, a very simple goal. The problem is steel is very flexible so it can just deform and can also chip under the abrasive, plus the abrasive also fractures which is a contaminant. Diamond hones remove some of the problems, used dry though they create others as the high friction tends to charge the particles and then there is static "gluing" of debris to the edge.
-Cliff
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Can we have this as a sticky please?!
The first time I looked at a Spyderco factory edge under a micoscope I was sure that the secret was in the burr removal. Since then I have maschined a quite a bit of copper which galls so badly that it has taught me a lot about burrs. It shows you, that it is essentially impossible to remove burrs without increasing the angle substantially.
 
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