Stropping, Steeling, Sharpening

[Garretts]

Laredo-
There is a lot of good information here on sharpening, but let me give you the short answer as to what I would do in your case. I would buy 2 fine ceramic rods and drill 20 degree holes in a 2x4 so the rods stand up in a Y configuration. (you can buy this I think) I would get one coarse stone from the hardware store- the coarser the better. Grind the deepest bevel you can (shallowest angle to the stone) on the coarse stone by using a circular motion. Do this until you feel a burr with your fingernail along the whole edge on the opposite side. Turn the knife over and do the same thing. Someone here probably has a better idea what to do about that burr on the one side, maybe you steel it out to make your life easier. I don't, I just start sharpening with the rods, about 50 to one hundred strokes may be needed. count the strokes on each side, keeping ANGLE consistent. Once the knife is getting sharp, LIGHTEN YOUR TOUCH A LOT. If you hold a steady angle and finish with very light touches, you should get an edge that causes hair to jump off of your arm when shaved. I am not recommending you test this way this by the way, but that is what I do. I look damn silly with a bald left arm, but hey, I am not vain anymore. Maybe one way to save arm hair is to take a known sharp edge and compare the edge you are working with by cutting paper. You may need to clean metal particles out of your ceramic rods, I do this with cleanser and the palm of my hand. I dry the rod completely before sharpening. I may do this 3 times when building a new edge.
I am sure there are better ways, but for the sharpening challenged like us, this might be easiest.
This works on my Spiderco knives, which seem easy to put a good edge on. My problem is still with cheap knives, easily remedied by throwing them away I guess.
Don't shave with a knife unknown to you, I am probably outspoken on this, but I think you could conceivably get infected by blood born diseases, and some skin infections I suppose. You will not find doctors reusing prep razors in the ER from patient to patient. (I hope)
Ok, so maybe that wasn't the short answer.
-I actually hold the rod at an angle in front of a protractor, being too cheap to buy the jig and to lazy to make one. This is a dumb way because it is so hard to hold a steady angle, but I seem to need the suffering to develop my character...

 

[Medic1210]

Originally posted by Garretts
somehow, I don't think this edge was produced by a kitchen steel.

Well, first off you don't use a kitchen steel to produce an edge, you use it to maintain that edge. All it does is draw the edge back in line after it warps with useage.

Second off, I don't buy the story of the leaves cutting themselves on the blade in the stream, unless the stream was a raging current (then only maybe). Sounds kind of like the movie Bodyguard where the silk scarf gets cut in half only by falling on the blade of a sword. Far fetched.

Mike

 

[Medic1210]

Originally posted by Cliff Stamp
Garretts :
quote:
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Will a perfectly sharp edge, in other words, one that comes to an infintely fine point, cut through any material with zero resistance?
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Yes.

-Cliff

There are some materials a knife can't cut through, so wouldn't the answer really be No? After all, he did say cut through "Any" material with zero resistance. Maybe some materials with zero resistance. I'm not challenging your knowledge of this subject, because you are far more knowledgeable about this than I am. I just think you missed the "any" part of the question.

Mike

 

[SAK]

I have been trying to decide between two steel setups - The Razor Edge Systems "Raz R Steel" (foldable) and a pair of smooth, hard, burnishing rods that are 3/8" in diameter (per a suggestion from Barry H). I wondered if Cliff or Medic or any of you other experts could help with 2 questions.

1) Is the diameter of the steels going to make much difference? I am not sure what diameter the Raz R Steel rods are, but I am sure they are less than 3/8". Just wondered if diameter would be an issue.

2) If I keep the angle consistent, is the actual angle I steel at going to be critical? I usually sharpen with my Sharpmaker and therefore sharpen at 30 or 40 degrees. If I use the 3/8" rods I could stick them in the Sharpmaker base slots and have the same angle. However, the Raz R Steel rods are preset at 35 degrees (I know I could remove them and set them in the 204 stone grooves but that sounds like a hassle). If I sharpen at 30 or 40 degrees will it hurt anything to steel at 35 degrees?

Citori - thanks for starting this thread.

Thanks,
--SAK

 

[swede79]

I'm not an expert, but do know these answers.

The diameter won't matter. What is more important is grooved v.s. smooth steels.

Don't confuse sharpening with steeling. When you sharpen, consistency is critical. When you steel, you only want an angle slightly greater than the one you sharpen at, and it doesn't have to be consistent, since you are merely bringing the edge back to true.

 

[Cliff Stamp]

Mike :

There are some materials a knife can't cut through, so wouldn't the answer really be No?

As I noted in the second part of the reply, this isn't a practical viewpoint, as you can't get a knife "infinitely" sharp. Just thinking of extremes, if the knife was infinitely sharp it is made out of some fairly odd material so assuming it is also infinitely strong, and hard etc. , then it would cut into any material readily, the "through" part as noted complicates the matter significantly though as geometry then comes into play.

In regards to being able to cut leaves in a stream, I have knives that can cut grass in a sweeping motion, no draw cut, just hold them perpendicular to the grass and push and lop all the grass off. Thus I can see slight leaves easily being cut by a sharp sword in the manner described. I would be surprised though if the edge that could do this was robust enough to take any kind of contact off of bone.

Garretts :

[sharpness]

What is the best way to measure this?

Cut something very slight, ideally under tension so it gets pulled apart and reduces the effect of geometry, and measure the amount of force required. A simple spring scale and a piece of thread will go along way into taking the subjective about of sharpness descriptions. For reference, the best production blades tend to come in at about 100 g on light baisting thread, this is rare and the knives are then so sharp they will shave will barely detectable pressure. As you move under 100 g the blades start to have very wild properties like being able to shave freestanding hair. Take the blade and hold it above you arm and it can still cut very fine hair. Double edged razor blades come it at as low as 20 g .

... does sharpness really equal cutting ability ...

Sharpness is one factor in cutting ability, just like the amount you can hold your breath is a factor in how far you can swim underwater. Sharpness determines how much force is necessary to *start* a cut in the material, the cutting ability is a measure of the amount of force required to cut *through* the material, and thus it is dependent on the blade geometry as well as the sharpness. Some materials are more dependent on sharpness (paper) and some more dependent on geometry (woods). But both are always factors.

... does the rough surface of an edge actually serve to "saw" some materials?

Yes, if you use a pull stroke and thus are slicing material as opposed to push cuts which have no draw. On a slice the teeth with sink to their depth, as you pull they tear or burst the material that is inbetween them. They again sink into the material and the process repeats. There are two distinct performance components; (a) the depth the teeth sink into the material, and (b) the force required for them to do so. These are inversely related (as one increases the other decreases) and thus there is an upper limit to the performance and you seek a compromise between how much material the teeth can cut, and how hard it is to make them do so. It is the same principles that govern saws in general, you will hear for example people talking about the hunger of a saw, which is how much wood it removes on a stroke. You don't just make a saw as hungry as you can, because if it becomes too high you won't have the strength to pull it through the wood.

Does this explain the drawing characteristics of even the best edges? That resting with their own weight on a material, they do not cut until drawn across the surface?

It explains why you usually get better performance with a draw, and why this gain in performance increases with the coarser the edge [there is another factor which is that as you pull a blade the material being cut gets pulled as well which opens up the cut as if the material was under tension, this is usually a small factor though].

Also, does this mean steels with a finer grain size like cpm 440v or cpm 10v have a greater potential for sharpness?

Yes, exactly right. However to see this potential you have to be able to sharpen a blade much better than most production blades, we are talking about performance that is much better than simply shaving sharpness. For reference of a limiting case see :

http://www.bladeforums.com/forums/showthread.php?s=&threadid=176372

-Cliff

 

[Greymoor]

I was wondering if I used the edge of my ultra fine stones on my sharpmaker. would giving several light strokes on each side of the blade act to realign the edge? I had planned to use this method to keep my knives sharp. As sort of a steeling/honeing step.

 

[Garretts]

Cliff-
Thanks again!
Let me know when you publish your first book on this topic. I will be your first customer. I read your referred to post and also some material on your web site. Great work!
Garrett

 

[Medic1210]

Originally posted by Greymoor
I was wondering if I used the edge of my ultra fine stones on my sharpmaker. would giving several light strokes on each side of the blade act to realign the edge? I had planned to use this method to keep my knives sharp. As sort of a steeling/honeing step.

Yes, you can do that, but it is a bit more aggressive than a smoothe steel. Just remember to apply no pressure. Just use the weight of the blade to draw out the edge.

Mike