Getting Rid Of The Burr

[Art]

We can get as technical as you want, and there are a set of properties for each steel. I have heard the term "knife steels" bandied around and it is a crock. Steel is made for industry, manufacturers don't really care what knifemakers want, they care what industry wants. Knifemakers have always chosen a steel or whatever that closely matches the properties they want for their knife. More Often, marketing comes into play and a steel is used because it is in vogue, more than if it is the best steel. Everything is a tradeoff when additives come into play. I like to know what steel I'm working with when I sharpen, but is it THAT important? No, I just sharpen it. I pretty well know what I'm working with when I get through a few passes on the grinder or stone, and hey, I have to sharpen it no matter what. Now, if I am making a knife, I would use 1065, 1075 or O-1, O-6, or L-6 for non stainless. I'm old school on that and I know exactly how these steels work. For stainless, the choices are a little more difficult. D-2, 440C, A-2, and BG-42 are my favorites, but the particle steels (CPM) are, while über technical, darned good knife steels also. Knifemaking (custom) has changed a lot in recent years. When I make a knife, I select the steel I want to use, and beat and or grind on it until it looks like what I want. I do about 90% of the finish work before heat treating it and testing for hardness (yes I have a tester). I do it all. Now a days, they select a steel and send their profile.file to the shop that waterjets or lasers their blanks. Then they send them out for heat treating, and when they get back, they finish them up. I talked with a current maker at a show about profiling his blanks, and he had no idea what I was talking about. Different business now. Not saying it is a good or bad thing, but what I am getting at is you are at the mercy of the maker when sharpening. You get one of those really hard steels and you just have to sharpen it, buck it up and get to work, I'll sharpen anything excepting maybe rock.

Art

[rickdroid]

You get one of those really hard steels and you just have to sharpen it, buck it up and get to work, I'll sharpen anything excepting maybe rock.

Art

What do you have against rocks;-)

OK, this series that you started has emphasized to me how little I know about the steel used in knives, what the differences are, why one type would be better than another --- and tons of other questions that I don't even know enough to ask about

To try and fill in some of the bigger gaps in my knowledge, can you recommend a good book or maybe a few that might give me a little more basic understanding. I'm not talking about some step x step knife making book but something that covers steel, what the differences are in different types, what the advantages and disadvantages of different kinds are and why one type would be more desirable than another. Again I am not sure what basic questions to ask in this area so assume that I don't know anything (you would not be wrong in that assumption) when considering any recommendations you might think of.

I figure that you could probably answer all these questions but taking up that much of your time, even though I would enjoy having my own instructor, would be pretty selfish of me and a large waste of your time.

Thanks for starting and hosting this forum, I have already picked a great deal and look forward to lots more.

Rick

[Art]

Hi Rick,

I have nothing against rocks, obsidian knives are wonderful cutting instruments, I think some ophthalmic surgeons still use them. A big obsidian hunter is also a thing of beauty.

Actually, my early schooling and subsequent training was in metallurgy, particularly in applied chemistry and metallurgy. I worked briefly in that field, but got into other things, but I digress. I would write a book on knife steels, but others have done a thorough job in an online wiki here. It's just a list of steels (some of them actually used in knives) and their properties. There is also the Lexicon of Blade Steels in the Pocket Guide to Knives which you can work through, and which I can answer most questions you will come up with. Basically Steels are a mixmash if Iron and various other elements like Carbon, Vanadium, Chromium, Tungsten, and other denizens of the periodic table that make-up what we may call tool steels, blade steels, knife steels, and then some names that are more 5th Avenue that descriptive or realistic. Read and enjoy, ask questions as your curiosity demands. I have a hard time explaining anything in less than a page or so, so bear with me.

Art

[BondoBobCustomSaddles]

Hi Bob,

The Burr is the thinnest part of the edge rolling over onto the side of the edge opposite the stone. It has to go to the side away from the stone as the stone will cut and remove anything on the side it is grinding. The stone moving toward or away from the edge makes no difference. The thinnest part of the edge, unable to remain upright, will be rolled over. It is not gravity, but the burr simply has nowhere else to go. Even if you use forward and backward strokes on a stone, if you are properly positioned with the stone grinding the edge, when you have ground as much as needed and go that fraction of a bit further, the burr will come up. While the burr is indeed good edge metal dieing, it lets us know that we have gone as far as we can on this bevel. As long as be don't bring-up big gnarly burrs, we can flip to the other side and the stone will remove the burr, of course the burr will come up on the other side, and then you are finished with that grit. The burr will always have grit all over it. Before going to a new grit, you have to remove the burr and the old grit. There is no problem with wiping the knife down (getting the grit and most of the burr off) and then stropping it to remove the burr before going to a finer grit. You will generally have bigger burrs with coarser grits. On final passes on say 1200 grit (everyone has their own grit system and it is confusing as hell), which is 3 micron or about an 8000 stone, the belt or stone is smoother than a baby's cheek and polishes more than removes more than a few hundred molecules, the burr will be indistinguishable for most, still, with the right angle, I can bring-up kind of a micro burr, I might need to look through a 30x loupe to do it, but it will be there. We seldom need this kind of precision for a head knife, but precision scissors are a different story. There is a problem with burrs though. It is easy to bring-up a "false" burr by rolling-up onto the edge. This is why I recommend jigs, and use them myself. This isn't easy with a head knife, so you have to realize when you are doing it, or that you can be doing it. As I have said before, there is some science here, but also a level of art.

When the stone has sharpened the edge to the point there is complete contact between edge and stone, there is no place for the burr to go but to the other side, complete contact keeps anything from getting between the stone and the edge. Complete contact is what we want, the edge is sharp.

So, it really doesn't matter which way the stone goes, unless the stone is less hard than the edge. Yes, the strop has to go over the edge, and away from it. Put power into the equation and the knife becomes part of a splitting machine.

After one of these knowledge dumps, I have to ask simply, did I answer the question?

Art

Hi Bob,

The Burr is the thinnest part of the edge rolling over onto the side of the edge opposite the stone. It has to go to the side away from the stone as the stone will cut and remove anything on the side it is grinding. The stone moving toward or away from the edge makes no difference. The thinnest part of the edge, unable to remain upright, will be rolled over. It is not gravity, but the burr simply has nowhere else to go. Even if you use forward and backward strokes on a stone, if you are properly positioned with the stone grinding the edge, when you have ground as much as needed and go that fraction of a bit further, the burr will come up. While the burr is indeed good edge metal dieing, it lets us know that we have gone as far as we can on this bevel. As long as be don't bring-up big gnarly burrs, we can flip to the other side and the stone will remove the burr, of course the burr will come up on the other side, and then you are finished with that grit. The burr will always have grit all over it. Before going to a new grit, you have to remove the burr and the old grit. There is no problem with wiping the knife down (getting the grit and most of the burr off) and then stropping it to remove the burr before going to a finer grit. You will generally have bigger burrs with coarser grits. On final passes on say 1200 grit (everyone has their own grit system and it is confusing as hell), which is 3 micron or about an 8000 stone, the belt or stone is smoother than a baby's cheek and polishes more than removes more than a few hundred molecules, the burr will be indistinguishable for most, still, with the right angle, I can bring-up kind of a micro burr, I might need to look through a 30x loupe to do it, but it will be there. We seldom need this kind of precision for a head knife, but precision scissors are a different story. There is a problem with burrs though. It is easy to bring-up a "false" burr by rolling-up onto the edge. This is why I recommend jigs, and use them myself. This isn't easy with a head knife, so you have to realize when you are doing it, or that you can be doing it. As I have said before, there is some science here, but also a level of art.

When the stone has sharpened the edge to the point there is complete contact between edge and stone, there is no place for the burr to go but to the other side, complete contact keeps anything from getting between the stone and the edge. Complete contact is what we want, the edge is sharp.

So, it really doesn't matter which way the stone goes, unless the stone is less hard than the edge. Yes, the strop has to go over the edge, and away from it. Put power into the equation and the knife becomes part of a splitting machine.

After one of these knowledge dumps, I have to ask simply, did I answer the question?

Art

As always, you got it covered.

Thanks,

Bob

[judgebc]

Okay, so I have rolled the burr?

Does this mean it is not sharp and won't cut?

Can, I feel or see it?

What power of loupe do I need to see it, any recommendations?

Do, I have to go to a 1200 grit stone, and re-sharpen it? 

I have a diasharp dmt extra fine, which I believe is 1200 grit/mesh/9 micron, is this what I use?

Thanks?

 

[Art]

No.

You don't "roll" a burr, you "roll" an edge.  You bring up a burr.  The burr is "brought up" because you have exceeded the intersection of the two bevels or planes and the excess has to go somewhere so it sort of stacks up at the intersection of the planes.  The burr does get pushed over a bit, that is why it is easy to feel (and see with a 10x loupe).  If you keep grinding past the point of intersection, the burr will get bigger and bigger until it finally will start to break apart, or in power applications possibly weld itself to the edge.  So STOP when you have brought up some burr along the whole edge.  Flip the knife and attack that edge with a finer grit which will grind away the burr and start polishing or grinding the edge to bring up a burr on the other side.  Wash, Rinse, and repeat till at the finest grit there will only be a miniscule burr.  This can be stropped off away from the edge at a 45 degree angle, or even a sewn buff charged with .50 micron green or even white compound.

Now, when you put a very thin and very sharp edge on a blade, like a straight razor, but I've done it with leather knives that I have got over zealous with, and you try to cut something that is beyond the scope of that edge, it could just be a piece of harder leather, the edge will roll over back onto itself and the knife will attain the cutting dynamics of a butter knife.  This is life in the quest for the ultimate edge.

Art