Feeling the bur

J

j.man

Joined
May 1, 2012
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I am a little confused what exactly to feel for when feeling for the bur. Correct me if I'm wrong but is it when the steel roles over. Are you supposed to continue to sharpen one side of the blade until you feel the bur then flip the knife over and sharpen the other side. How many times do you repeat the process?
 
At a minimum, once you've detected the burr on one side for the first time, you should 'flip' the burr to the other side at least once. I usually go back & forth at progressively lighter pressure each time, to both flip and thin the burr as much as possible, before moving on to the next finer grit. I repeat the same sequence with each subsequent grit so, by the time I've gotten to the finest hone, there should be an absolute minimum of burr left, small and thin enough to remove by stropping (ideally). If the burr isn't flipped enough times, or thinned enough, it'll be very difficult to remove it all by stropping alone.
 
j.man said:
So the bur is when the blade rolls over?
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That's essentially what it means. The edge gets thin enough from sharpening, that it no longer holds up to the pressure exerted against the hone, and it will roll or fold to one side (away from the hone).
 
Obsessed with Edges said:
At a minimum, once you've detected the burr on one side for the first time, you should 'flip' the burr to the other side at least once. I usually go back & forth at progressively lighter pressure each time, to both flip and thin the burr as much as possible, before moving on to the next finer grit. I repeat the same sequence with each subsequent grit so, by the time I've gotten to the finest hone, there should be an absolute minimum of burr left, small and thin enough to remove by stropping (ideally). If the burr isn't flipped enough times, or thinned enough, it'll be very difficult to remove it all by stropping alone.
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I was gonna respond to this thread, but this pretty much sums it up...

I would follow this advice :thumbup:
 
Only, I would not let a burr get large enough to 'feel' as then it becomes harder to deal with (remove). If you'll use magnification and a bright light during sharpening or sunlight and check often. This will allow you to catch it earlier and progress to a littler finer grit and strop to remove it. DM
 
I think when learning to sharpen its good to form an obvious burr because it is a positive indicator you've apexed the edge. As you progress in skill its definetly better to form the smallest possible burr.

If you're using a coarse stone, the burr will be easily visible if you look closely at the edge. You can also feel it by running your fingertips off the edge; the burr will grab at them. Also if you cut something like a paper towel with a burr hanging on the edge, little bits of fluff will stick to the burr which make it easy to see.

As for removing the burr, I've recently started using this technique: Once burr is formed from each side on coarse grit, move to fine grit and make two alternating passes very lightly at a high angle, as though you were microbevelling the edge. This will cut off the burr and remove weakened metal from the apex. Then return the angle to normal and sharpen on the fine stone using alternating passes until the tiny 'microbevel' is gone. Its critical not to take off too much metal when making the high angle passes, or else you have to go back to the coarse stone.
 
I'm good with that. 'At first'. Yet, I wish someone would have taught me an easier method. DM
 
I like to draw the blade through some wood to scrape off some of that burr. Then touch some very light stokes back on the stone. As you progress up the grit number, the burr will be smaller and finer. You can feel both burr and toothiness at lower grits. At the high grits, pulling that edge through some wood should be very smooth and offer little resistance. That means you have gotten that burr off and put a fine edge. This is not a test for sharpness but does give you a good test of how much burr is on there. On your first pass through wood, you will see a black mark left in the cut...that's the steel from the burr left behind.
 
Sometimes you can see it clearly and feel it with your fingernail. That's a big burr that needs to be worked on. But sometimes it is small and impossible to see with your eye. You can still sense the burr by trying to cut newspaper print (it will get caught and rip the paper). Another trick I've heard of (but haven't tried myself) is fluffing out the end of a Q-tip and running the cotton fibers gently along the edge. They will get caught on the burr and break off. You know there is no more burr when you can slice through newspaper print with ease and no catching. Or if you have a powerful microscope.
 
Magnaminous_G said:
Sometimes you can see it clearly and feel it with your fingernail. That's a big burr that needs to be worked on. But sometimes it is small and impossible to see with your eye. You can still sense the burr by trying to cut newspaper print (it will get caught and rip the paper). Another trick I've heard of (but haven't tried myself) is fluffing out the end of a Q-tip and running the cotton fibers gently along the edge. They will get caught on the burr and break off. You know there is no more burr when you can slice through newspaper print with ease and no catching. Or if you have a powerful microscope.
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This, and variations on this theme...the Q-tip...is a good way to detect even the smallest burr. I have some old Duofold material...old longjohns...cut up into squares. It's wool on one side and cotton on the other. When swiped over a dry cloth, wool side, spine first, at approximately the same angle as the cut, I can feel the burr pull at the cloth. I can also tell which side I sharpened last if I forget this way. This is a good method and I am sure a Q-tip or cotton ball would work great...something that the burr will catch on.
 
Robs92XJ said:
I think when learning to sharpen its good to form an obvious burr because it is a positive indicator you've apexed the edge.
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This is VERY good advice. I've also found that I tend to form a burr on *part* of the edge, but not all of it and then I stop. This is a mistake. I should continue until I feel/see/etc a burr on the entire edge, from hilt to tip. Once I started doing this, my edges went to a different level. This is basic, but it bears repeating. Sometimes I feel like a perpetual beginner.

As for removing the burr, I've recently started using this technique: Once burr is formed from each side on coarse grit, move to fine grit and make two alternating passes very lightly at a high angle, as though you were microbevelling the edge. This will cut off the burr and remove weakened metal from the apex. Then return the angle to normal and sharpen on the fine stone using alternating passes until the tiny 'microbevel' is gone. Its critical not to take off too much metal when making the high angle passes, or else you have to go back to the coarse stone.
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More very good advice and contains information (about forming and removing the microbevel) that I hadn't considered. Good post Robs92XJ!

Brian.
 
Thanks. That advice was gleaned from Cliff Stamp's site. It makes sense to me and seems to work faster than the other method of burr removal which is to make alternating, ever lighter edge-leading passes. But I have only recently begun using it, so I am not going to say it is the superior method yet. I certainly haven't done any kind of rigorous comparison.

The comment about being a 'perpetual beginner' resonates with me. I know that the ideal would be to sharpen so that no burr is formed, in other words the last pass you make on each side would be that pass which removes the last bit of roundness from the edge, along the entire edge. Any futher passes would only create a larger burr and waste time, energy, and metal. In practice there are at least three things that prevent me from doing this. One, if there is damage on any part of the edge I am compelled to remove it, which means I have to take back the entire edge until the damaged part is removed, so all of the undamaged portions are sharpened beyond the point where they are just apexed, which means I've formed a largish burr.

Two, I still have occasional issues matching the edge angle along the belly curve; usually I end up too acute towards the tip (not raising the handle enough) so I will have apexed towards the heel before the tip. This can lead to a largish burr forming near the heel, if I'm not paying close attention. If I check the edge frequently I can correct this before it becomes an issue and before I thin out the tip.

Which relates to the third issue, paying attention and not zoning out on the repetitive motion. I started sharpening on scandi grinds that take frequent damage and require a long time to sharpen; I got used to zoning out. Go from that to sharpening an Opinel with a barely visible edge bevel and it seems like you're done before you even begin. I am still readjusting my perceptions of how long I should spend on each stone.

Only the first issue is substantial, the other two are a matter of skill and focus. Anyways, as it relates to this thread, forming an obvious burr is probably telling of an 'amateurish' skill level, but it works to ensure an apexed edge and there are multiple methods of removing the burr. It's a mostly a matter of (in)efficiency, but as the saying goes, first you get good, then you get fast.
 
I guess it's all a matter of subjectivity, because I can feel burrs with my fingernail that are much too small to be seen with a 30x loupe or pull off cotton fibers. One good way I know of that's not often discussed is that, if the edge shaves while one side of the blade is upturned, but not while the other is, then the side of the blade that shaves when upturned probably still has a burr on it. I discovered this because a lot of the times burrs will be super sharp, shave, cut phone book paper, all that good stuff but degrade very quickly with actual use--I think this is why removing on hardwood is so useful. But to save time I just shave arm hair with each side of the blade upturned, and if they both feel the same and I can't detect a burr with my fingernail, I move on to the wood then to make sure I'm taking off any wire edge that's simply been stood "straight up".

I think that mostly once you get really familiar with things, you don't really need to raise much of a burr at all to be able to tell you've met the two edges together, a lot of the time I can tell by feel or just use my better judgement with "That's probably all right." A lot of it is simply that after done honing, I generally do several light-pressure, alternating strokes to make sure whatever burr is on there gets wiped off, and it's generally pretty intuitive to know when it's gone.
 
I cannot imagine being 100% certain of grinding a fresh apex without raising a burr - however small. The difference is in the ability to 100% detect and quickly and reliably remove it. Having ready access to a microscope capable of 1000x has definitely shaped some of my opinions. I find no formulaic methods work reliably for me. The burr must be observed/detected and removed in detail. After that if desired, a final polish of some sort can further shrink the cutting edge without simply working on the burr.

A final thought - if the base of the burr is small enough, say a micron or less, then it can be removed through use and you'll never know the difference if you're going for a utility edge. Only if you're going for max possible keenness at a given grit do you need to completely eradicate it. The burr will effectively prevent the apex from being polished finer.
 
j.man said:
What exactly is a apexed edge.
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When the slopes of the bevel have intersected in a infinite space. When the distance between the intersection is limited by the material and the particle size of the abrasive grinding it.
 
Apex is the perfect intersection of two planes meeting at the edge. Theoritically it should only consist of one molecule.

That's why Jason said 'limited by the abrasive particle size', which is reality vs theory above.
 
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