quick BURR question

A

AmadeusM

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If a person sharpens away from the edge, toward the spine, will the burr still form?
 
Yes, it will. Maybe not as much and maybe of a differnt type (you can read Verhoevens treatise on sharpening and burrformation) but you will still get one.
 
No, it will not.

Burr is a thin layer of steel who "bends away" from the sharpener because there is nothing behind it but air.

If you move your sharpener against the edge in the direction of the neck of the knife, and only that, you will not get any burr. That because there is no place for it between the sharpener and the steel blade.

Thomas
 
If a steel is prone to forming an extensive burr, some are and some are not, it will form regardless of you hone into the edge or trailing, this has been known for quite some time, as is the fact that edge trailing tends to be more prone to burr formation. Verhoeven has pictures of edges under magnification which show both techniques of Hob noted. There are many things you can do to minimize burr formation during sharpening if this is a desired goal and there are reasons both for and against doing so.

-Cliff
 
During the sharpening process, aren't you basically making the burr stand straight up? You are basically controlling the burr.

I prefer a clamped sharpener for keeping a consistent angle (Edge-pro/Lansky/Gatco). I sharpen the edge back and forth (towards and away from the edge/spine) using coarse stones (where a majority of the material is removed). The finishing or fine stones tend to work better for me when I use them going towards the spine of the knife only.

If you let the burr fold over to one side or the other, you can have a razor edged burr. Problem is, the burr will continue to fold over very quickly with use. Then your edge will be round, and no longer razor sharp.

AmadeusM-
Experiment with sharpening. Try the method you talk about in your post (just sharpen towards the spine). Test your results. Then, try sharpening the knife towards and away from the spine. Test your results. It would be interesting to hear your results.

1. One of the easiest ways to see if you have a burr is to hold your knife under bright light with your edge facing towards you. Look for a white line on the very edge of your blade. If you see one, it's the burr folded over to one side and reflecting light.

2. Try cutting newspaper with and against the grain (just rotate the newspaper 1/4 turn). If your edge hangs up at any point, you know you have a folded over burr, or at least a partial burr folded over in some spots.

3. Shave arm hair off both arms. In other words, lay the flat of one side of your blade on your arm and shave. Then take the knife in the other hand and lay the flat of the other side of your knife on your arm and shave. If it doesn't shave on both arms, you have a burr folded over to one side.
 
EdgePal said:
That because there is no place for it between the sharpener and the steel blade.

Thomas
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The burr will form, regardless of technique, on the side OPPOSITE of the hone :rolleyes:.

The reason why you get less of a burr in the edge leading technique is according to Verhoeven due to the fact that you are carrying material away from the edge, while with edge trailing you are carrying debris to the edge. However, especially at low honing angles you will thin out the edge enough that it will "roll" AWAY from the hone (the impact of the abrasive particles bend the steel essentially away). The softer and "rubbery" the steel, the more likely this is going to happen. A carbon steel at 64 Rc forms practically no burr at all, because the edge doesn't tend to roll very much, while for example something like 420HC is among the worst in my experience.

Burr control means usually that you increase the honing angle so that you are pressing against the "root" of the burr and cut it off right there instead of moving it from one side to the other. Important is also that you don't let the burr become to large. If you continue to hone too long on one side the burr will get very large and floppy and becomes to more difficult to "cut" of. Instead you are moving it back and forth till it breaks of, usually leaving a pretty crappy edge. This not too much of a problem though you just continue honing till you have reestablishe a new edge this time hopefully to a point where you haven't build up the burr again.

Essentially, most people agree that a technique following the basic principle of: 1.) forming a burr to make sure that the old edge is removed and that the edge is fully set, 2.) Intentional "blunting" to eliminate the burr by increasing the angle or by whatever other means, 3.) honeing on fine grit just to the edge without reforming the burr is the best way to sharpen from a blunt edge. These are of course just the basic step. Especially step 3.) is not so easy to do in practice.
 
My experience is the same as Cliff and HoB, yes, you will get a burr for the reasons mentioned above.
 
So here is a question. The other day on my Kabar heavy bowie, I managed to remove the burr from my blade (along with some tiny chips; it was a "Huge" accomplishment for me), but now my knife seems to be about sharp enough to cut crud; it can barely cut paper and definately can't shave hair. Try as I might I can't seem to get it sharp again. I don't know if I could even form another burr if I wanted to. Any pointers?

Thanks for entertaining a newbie.
 
HoB said:
A carbon steel at 64 Rc forms practically no burr at all, because the edge doesn't tend to roll very much, while for example something like 420HC is among the worst in my experience.
Click to expand...

Hardness is definately a factor, but carbide and grain size has a massive influence as well. One of the best knives I have seen for burr formation was a chef's knife in 420HC from Wilson, which was heavily used. I gave it as a wedding gift several years back and it was not sharpened since then. It was so dull the edge was reflecting light heavily its entire length and it had no cutting ability at all. Now the edge should have been very prone to forming a burr because there was so much weakened metal, but it wasn't. I formed the edge with the coarse side of a cheap hone, and actually stopped and had to check it under mag because a visible burr didn't form when all the weakened metal was ground off. It was even clean under mag, not a hint of a burr. That was a nice knife to sharpen, the steel was easy to machine, the edge was thin and acute and it didn't tend to burr.

-Cliff
 
HoB said:
2.) Intentional "blunting" to eliminate the burr by increasing the angle or by whatever other means
Click to expand...

Just so I'm on the same page...

Are you talking about the technique where you do most of the coarse stone burr formation at a shallow angle? Then, you increase the degree of your angle to finish the burr formation with the less coarse stones?

I think this works well.
 
Yes, that is one way to do it, but I found that you can form a burr that is difficult to cut off with the fine hone. I have become quite fond of Jeff Clarks method of increasing the angle on a medium hone by at least 5 if not 10 degrees (I don't really measure that I simply increase it by an arbitrary amount) and remove the burr with a couple very light passes. After that I know I might have to hone a little more on the next finer stone to have the two sides meet at the original angle but at least I can be sure I don't carry a burr over to the next finer grit. For my last few strokes on my finish hone (Usually I use 3 hones in total 700, 2500, 10000 (medium, fine, finish). If I have to make changes to the bevel I might start at 220 (coarse)) I always increase the angle by a few degrees. That is as much to control any remaining burr, as it is to guarantee that I work on the edge since I freehand and there is always a bit of slop in the angle. The finish hone is so fine that it doesn't alter the geometry appreciably.

Cliff: I really know only 420HC as Buck runs them, and the models I have are pretty old, too. So my experience with 420HC is limited. I sharpend 5260 which is supposed to be 58Rc and it behaved beautifully. Just as you described: very easy to grind and hardly any burr at all. So I agree, hardness is not the only factor here, I was simply trying to give a drastic example.
 
HoB said:
I really know only 420HC as Buck runs them ...
Click to expand...

I have used that, Wilson's isn't similar. I would not have guessed it was 420HC by honing it, it didn't get that drastic burr that can form on the softer stainless, first time I have seen that behavior. He does HRC test them and they are about 55/56 HRC which makes me wonder just how hard are the AUS-6/420HC blades commonly used in production knives, do they actually meet the factor specs.

As a side note, the tip pointed to 420HC as it had a permanent bend of about 45 degrees to the right for about half an inch where it was used in an attempt to pry apart frozen food. That kind of ductility is hard to get in high carbon stainless, though may be possible because he grinds them so distally tapered. I straightened it readily.

-Cliff
 
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