Razor sharpness compared to other types of blades

**burns420** · 07-26-2010, 01:17 PM

I always thought straight razors were about as sharp as a blade could get, but I've been told by a couple buddies that they aren't nearly as sharp as a scalpel or a Katana sword(or a couple other types of swords). I know it's possible, but I find it unlikely that these other blades can be significantly sharper.

I know the point of a straight is supposed to be a comfortable as well as sharp edge, but with the high quality steels used in them able to take a sharp edge with a narrow bevel, is there much room for improvement(in sharpness)?

I've seen some sharpness tests mentioned for comparison, like a loop of thread attached to a weight that shows the force required to cut the thread. But haven't seen results comparing different blades. Anyone have any info?

**Stubear** · 07-26-2010, 02:21 PM

Bear in mind here that those blades are for different purposes.

A scalpel is for surgical operations, a katana is for slightly less accurate operations that dont require the subject to be walking around afterwards and a razor is for removing hairs on your face.

I've handled scalpels in the past that were certainly sharp enough to shave with, and I've used kitchen and pocket knives that could remove hair from your skin, but I wouldnt want to shave with either of them.

A straight razors edge is not necessarily any sharper than a scalpel but it is finer and wouldnt hold up to the same use as a scalpel or katana. Try using a straight razor for surgery and it would be dull in no time at all.

The razors edge would also be a lot smoother than either a katana or scalpel, simply because it needs to be in order to provide a comfortable shave withour wrecking your face.

A piece of steel will only get so sharp/thin before the edge collapses, and as Glen often says, anyone can make a piece of metal sharp. Smooth enough to shave with is another story!

I would also tend to disagree with the statement that scalpels are sharper than straight razors because I've handled both scalpels and straight razors and I know which one is easier to slice myself on..! You can touch a scalpels edge by mistake and get away with it if you're lucky. Touch a razor and it'll open your finger up like a piece of over ripe fruit every time..!

I'd be interested to see if there is any empirical data on this though.

**JeffE** · 07-26-2010, 02:49 PM

Um, I always thought that Romulan battleaxes had the sharpest edges possible:

http://www.youtube.com/watch?v=XtdLTEr2r3Q

**smokelaw1** · 07-26-2010, 03:11 PM

Yuck. Canned goo. Oh, and the fact that he was shaving with a battleaxe. And a 45 degree angle? Ouch. I mean, it's like his dad never taught him to shave witha battle axe.

**burns420** · 07-26-2010, 03:14 PM

Is that vid fake? Looks like when he was lathering up and the camera jumped ahead his face was clean shaven and just covered with lather. He probably then put the hair into the lather or something to show it coming off his face.

Anyways, yeahi know they all have different purposes and need different edges but I just want to know if they were all put through a standard test of sharpness. Like the thread loop test I mentioned, which blade would be the sharpest. I don't care of it dulls after one cut or stays sharp forever. This is a small bet we've got going, but would need some solid proof to decide.

**Library Guy** · 07-26-2010, 03:22 PM

Scalpel is a very broad term. Most of us have seen a basic Steri-Sharp™ plastic handled scalpel with a permanently 'loaded' #15 or #10 blade. While a useful clinic tool, this is the Bic razor of scalpel world and shouldn’t be confused with the array of tools being used in the operating room.

Modern manual surgical cutting tools are made up of reusable handles and disposable blades each fashioned for a particular task. It would not be far off to compare them with DE razors. In fact Feather of Japan makes many surgical blades.

Before lasers, the blades used for eye surgery were very sharp, very thin, and yes, very fragile.

So, some surgical blades are going to be sharper than your straight razor (or katana) but keep in mind they might be swapped or changed after only a few cuts.

**pcdad** · 07-26-2010, 03:32 PM

OMG!...thats guts I think..hmm..lemme just look into my chest of stainless steel "objects" to compare

pcdad

**JeffE** · 07-26-2010, 04:29 PM

Apparently, there's lots of these axe-shaving guys out there. Don't mean to hijack this thread, but shouldn't Lynn think about starting another website to serve this community? I'm thinking something like www.axerazorplace.com or www.triedtoshavewithanaxebutcutmyearsoffinstead.co m

YouTube - When a razor just won't do.

**kevint** · 07-26-2010, 11:09 PM

The fragility of the razor's edge is more related to its low bevel angle that its width dimension which may be .3 to .5 microns or something like that

The Tennessee toothpick was said to have one side w/ fine sharp edge the other more obtuse, for different uses. The japanese sword too saw different uses sometimes used against Jpn armor, foreign armor, or unarmored duels. There are some differences in cross sectional geometry from era to era, so do doubt there were different edges and final edge dimensions. Most likely they were as sharp as they could be for a given use.

If you are using a polish plane or similar finished-surface woodworking tool the solution for a chipped edge is typically to resharpen at a higher angle not to make it less sharp. Those edges are often just as fine dimension wise as the razor .5 micrometers of there'bouts. I dont see why a "katana" could not be as well; the best hope -a sword meant for unarmored dueling fresh from a highly skilled polisher, working on a very well made blade

Nevertheless a straight razor is typically as sharp as steel can get

**Sticky** · 07-27-2010, 02:32 AM

Assume you have a sword, straight razor, and a scalpel made of the same steel. Sharpen each at the same included angle on the same hones. All will have the same edge sharpness... The only differences will be because of the blade thickness (i.e. the razor will flex more).

Keep narrowing the included bevel angle until the edge starts to chip or roll too easily. Increase the bevel angle slightly to obtain the maximum (in theory) sharpness available to the steel in use.

There are some "high tech", expensive sharpness testers available. The testing media used by the machines has to be very uniform and the standards are not very well agreed upon. Sort of a very niche product. Sharpness tester.

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