Surgical scalpel and sharper is what I am looking for .
I don´t know if this will be practical in your case, but when I need the very best sharpnes for delicate work on my model airplanes I use blades from disposable razors; with some practice it´s easy to pry them open.
Those blades win hands down against anything I´ve ever tried (and I´ve tried almost anything!), the downside is that they are a little unwieldy and very flexible, although that can be an advantage some times.
Surgical scalpels with replaceable blades can be purchased at art/craft stores. Swann-Morton are the most common brand here in the UK.
Not cheap, but Obsidian scalpels are the sharpest blades known.
These guys sell Zirconia Ceramic (pdf) blades for much cheaper. Somewhere I read they are 100 times sharper than steel.
Good 'nuf?
-Tcat
Just a side note, but I remember being told that butchers’ knives are sharper than surgeons’ scalpels. The rationale was that you want the scalpel to have a modicum of bluntness so that it crushes capillaries shut, to reduce bleeding.
Just about any hardware or hobby shop will carry craft knives. A common brand in the U.S. is the X-acto line, which offers a wide variety of both blades and handles. Here are some examples.
What’s wrong with your Crysknife?
What is your cutting desire?
Very sharp but very fragile and only suitable for cutting very tiny things very carefully? Opthalmic scalpels might be a good fit. Unfortunately, these beasties can be hard to find and are pretty specialized.
Regular scalpels (the classic “ten blade” they’re always asking for in medical TV shows) are easy to find and IME, a smidge sharper than the X-acto hobby blades. They’re also not quite as durable.
BTW: a #10 blade has a round tip, and the typical X-acto blade is a #11, straight and coming to a sharp point.
X-acto baldes ar enot particularly sharp. What I use in my hobby (model building) is a scalpel with #29 blades. There are a number of places on the Web where you can get the blades. I buy them a hundred at a time, since they tend to be fragile. Thehundred last me several years.
There is always someone who prefers to be a cut above the rest.
Muad’Dib, you haven’t said what task the blades will be doing. The sharpness of a blade depends on how it was last sharpened. You can get an axe sharp enough to shave with, once you learn how. If you need a short, thin, disposable blade, I agree with previous posters.
If you need something “razor sharp,” you can still buy straight razors. The final hone is done with a leather strop, and scalpels are not going to have a finer edge than that.
So, what do you need? You pays your money, and you takes your choice.
I use #21’s.
I don’t try for durable. When they stop cutting nicely, I slide them off into a sharps container and put on a new one. Particularly if I have to do intestines or a the neck. You should always put on a new blade before doing a forensic neck.
I have mentioned this company before - I do not own stock in them, I swear. I don’t know whether they are at the top or the bottom of the price range. But it’s Hallowe’en, and I can’t see any better reason to mention Mopec.
Boy if I only had a dime for every time I’ve heard that one.
So does the morgue do anything special for Halloween? Dress up like corpses perhaps?
The sharpest knives in the world are diamond knives. These are used for sectioning materials for viewing under microscopes. They are good for cutting things in the 50nm up to one milimeter range, and run you about $1,000 up to $3,000-$4,000.
If that’s still not sharp enough you can get oscillating diamond knives used for sectioning things before they go into electron microscopes. These can cost $10,000 or more.
Both these knives are extremely brittle and are only really good for the appointed tasks. They don’t look much like knives, and unless you are looking to do something on an extremely small scale they are useless.
Most diamond knives cut somewhere at a 35 degree angle.
Next up are knives made from volcanic glass. These can be extremely sharp and will be useful at angles from 40 degrees down to 11 degrees. Consider that at 11 degrees they will be so incredibly brittle that they will be useless for most aplications where they will encounter any stress.
Ceramic knives are a further compromise between durability, brittleness, and sharpness. They are both durable and sharp but still relatively brittle.
When you move into metals truly interesting things start to happen. Molybdenum is very flexible and non-brittle and can take a very sharp edge. It is however very soft, so the edge doesn’t last very long and isn’t good for all materials.
In fact, no edge material or angle is good for all purposes. Asking for the “sharpest knife” is kind of a useless idea. Contrary to popular thought, a razor edge on an axe is not a desirable trait. An axe edge will be made a very hard but nonbrittle material with a severe angle to attain maximum utility and cutting power. A razor edge would shatter or deform almost immediately.
What this should all be telling you is that you need to ask “to what purpose will I be using this instrument?” When you ask that question I can meaningfully tell you what instrument and edge type will perform with maximum utility.
All that aside, I will try to give you some practical and useful advice on edges in general. Razors and those type edges are usually high moly steel good for shaving and what have you but losing the edge quickly under other usages and usually subject to deformation under stress and sometimes breakage which can be very dangerous.
For our purposes we will arbitrarily divide the best edges into three categories dependant upon their usages.
- Impact edge.
The impact edge is the type of edge and material used in things like axes, lawnmower blades, and what have you. These edges are typically very steep edges made from very durable materials with high hardness and lower deformation characteristics.
- Tool edge.
A tool edge is typically made from similar materials to the impact edge but with a shallower angle. It accomplishes its action through pressure rather than directing the force of an impact. Machine tools and finewoodworking chisels would be examples of tool edges.
- Cutting edge. A cutting edge accomplishes by neither pressure nor impact, but actually by a sawing action. These are shallow angle irregular edges that are less durable than either of the aforementioned. Most utility type knives and kitchen knives and razors fall into this category and this is what people thing of when they think of “sharp.” Because this is what most people are thinking of when they are thinking of sharp, this is what we will focus on.
Commercial kitchen steel is typically excellent steel for most applications and for holding an edge. Most domestic kitchen steels are much harder and more brittle than commercial steels but hold an edge longer.
Any knife or razor that you buy will tend not to be very sharp as far as commercial standards are concerned. This is simply because the knife was most likely designed for durability and the taking of an initial servicable edge.
If you want extremely sharp instruments you will need to make the edges yourself. To do so, you will have to cut away the old edge and replace it with the one most useful to your purpose. If you are going to use pressure or chopping action you will want a harder less flexible material and a steeper angle. If you are going to use slicing action you may wish for higher flexibility in your material, a softer material and a more shallow angle.
For the former application the best system is what is known as “scary sharp” which describes a process of putting an edge on a tool using ultrafine abrasive sandpaper. Yes, sandpaper. Don’t laugh. It puts storebrought razors to shame.
You can read about it here:
http://www.woodbutcher.net/scary.htm
or here:
You can do it yourself from those links, or google it and you will find all manner of folks willing to sell you kits to put this kind of an edge on an instrument.
If you want a cutting edge, for my money there is really only one way to go. With good steel you can easily exceed the sharpness of a razor many times over. This is the Woodcraft Razor Sharp Edgemaking System. On top of absolutely spectacular results it’s also very quick and very easy for cutting a variety of edges into your tools and knives. I have a kitchen knife that I can, no kidding, just wave at onions so that they will fall apart.
The system consists of two paper wheels that you install on a bench grinder. You will need to dedicate the bench grinder to this purpose and I recommend buying a good grinder with adjustable guides and I strongly recommend safety gear like gloves and glasses and a canvas apron.
Your grinder will spin at 3500 rpms or so, flying grit and particles of steel can blind you. If a razor sharp knife gets away from you on one of these wheels it can launch with terrific velocity. The way these things work it will launch straight at you, so you need to be careful!
The system is two paper wheels. One has a fine grit on it. You apply a special wax to the grit wheel which both lubricates and reduces the depth of the grit making it for your purpose finer than it is. Using this wheel you quickly go back and forth so you don’t heat up your blade cutting out the old edge and installing a new one at the desired angle. You do this on both sides until you raise a “wire” along the edge. Once you’ve raised a wire (you’ll know what I’m talking about the first time you see it,) you proceed to the second wheel. This is simply a paper wheel with serrations for ventilation. You apply a very fine jewelers rouge to this wheel and buff out the edge. This gives you a far superior edge to mere stropping (which simply aligns the serrations created by honing,) as you will actually make this edge a degree or two steeper, both polishing the previous edge and creating a second finer, steeper edge.
With a little practice (holding the angle constant is the key) you will have edges on most everything far beyond anything you’ve imagined possible.
You can buy this sytem here:
http://www.woodcraft.com/family.aspx?FamilyID=219,
and is what I would recommend for the neophyte who wants extremely satisfactory, super-sharp edges, though the fact of the matter is that I think scary sharp has the potential for a slightly better result but with so much more work that the law of diminishing returns applies and you are unlikely to get a good result until you’ve put in much practice and experimentation and gained experience with the process.
If that’s still not enough I can recommend you several volumes on sharpening for different applications.
-Scylla (Who worked in a sharpening shop in high school)
Funny, you actually got me lol 
I imagine I will be using them for a variety of purposes, but initially it will be for cutting very thin plastic.
I’d opt for the x-acto like one at the bottom of the page depending on price. Steep??
The #11 is my personal preference and I keep it honed sharp on several sharpening stones of progressively finer grit. If it breaks or sharpened till the edge becomes too ‘thick’ it time to trash it. They are cheap and good for many a cut.