How To Detect or Remove the Micro Burr?

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kreisler

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May 11, 2012
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I enjoy freehand sharpening and even developed my own technique which i call 204-freehanding. In the past 2yrs i successfully freehanded hundreds(!) of various edges (EDC knives, kitchen knives/machines/cutlery, gardening tools, other cutting tools, etc.) to scary sharpness and in all modesty ;) i'd call myself an experienced sharpening dude not a beginner anymore! But it wasn't until recently that i really learned about the 100.0% detection and 100.0% removal of the burr. This was so mind-blowing (because i was thinking that i knew it all) that it's worth sharing.

During the sharpening process, how do we check for sharpness, for progress?
Imho the most efficient way is to try to light up the apex 'from above' with a directed light source. For example you could wear a headlamp (Olight H1 Nova), hold the knife vertically with the apex facing your chest, then slowly rotate the blade away from your chest. The apex will eventually face your eyes and you would see light reflections bouncing off the dull spots/sections of the apex line. The sharper the knife, using any diffuse light source like daylight won't cut it, you will need a small powerful flashlight for this 'flashlight trick'.

The 'flashlight trick' can tell you within a second which 1mm spot still needs some work.
But here comes the first lesson. A light-reflecting spot (or section) of/on the apex can mean two(!) cases: The spot is either still dull/blunt/rounded or damaged or alike, or you're seeing the light reflections from a macro burr formed at that spot! Either way you're not done yet but keep working accordingly until the entire apex stops reflecting any light 'from above'. And that's then the point where i used to call it quits, rightly so because the edge would cut tomato skin and phonebook paper beautifully. So where's the problem?

You wouldn't expect or believe it, but most likely there is still a micro burr at/on the apex!
So do check with your thumb after all, on either blade side, and be honest to yourself! And if you can or cannot feel it, we come to the second lesson: the 'flashlight trick' is not complete until you check the edge 'from behind' on either blade side. Hold the knife horizontally parallel near your chest, with the spine facing your body. Then slowly rotate the knife axially, turning the blade downwards. At some point your headlamp's light would hit the edge at a perfect angle 'from behind' such that the micro burr reflects light into your eyes. Wow, what a revelation, just crazy!:eek:

Now we are ready to formally distinguish and define macro burr vs micro burr.
  • macro burr is so big that it produces visible light reflections (in direction of the light source), if directed light hits the apex vertically 'from above'. macro burr ("macro wire edge") can be easily felt with your thumb and it can be reduced and eventually broken off through alternating balancing strokes. If you see broken off "wire" on your stone, that's macro burr. As soon as the apex stops reflecting light in the aforesaid manner, congrats you broke off all macro burr and your knife edge is scary sharp. And you could call it quits here. Note: Depending on the steel, macro burr cannot be reduced and/or removed through a loaded leather strop; it's not the way to go.
  • micro burr is by orders of magnitude smaller than macro burr; so small that it produces invisible light reflections (in direction of the light source), if directed light hits the apex vertically 'from above'. Fortunately, micro burr ("micro wire edge") can be easily felt with your thumb, too. And with a focused/powerful light source directed 'from behind' at a proper angle it can be made visible, luckily (and who would've known?). I posted a helpful photo on Page 2! The ambitious perfectionist will look for it and try his best to remove it. Note: Typically micro burr is extremely persistent and is even raised by balancing strokes on Spyderco UF wtf. It can be very challenging and time-consuming to try to "pluck the micro burr off the apex" while not raising fresh micro burr.
Summary. Coming off the Spyderco UF your edge is scary sharp and good to go but the apex still carries a micro burr (depending on your blade steel/hardness, actually), very hard to see during daytime but easy enough to feel with a sensitive thumb. Removing a persistent micro wire edge can become extremely challenging and can only be accomplished by experienced practitioners. Feel free to ignore the micro burr but don't wonder if the edge dulls a bit faster than the factory edge!:poop:

Btw this OP is not about deburring techniques, but my personal repertoire includes dedicated freaky deburring strokes on a portable ruby, very light edge-leading strokes on ceramic, very slow edge-leading strokes on ruby (possibly at higher angle), edge-trailing strokes by a loaded narrow wood strop, and much patience. In principle there is no difference in technique for removing macro burr or micro burr. And some practitioners don't even distinguish between the order of magnitude of burr size; to them macro burr is burr, micro burr is burr, same same ha ha, and burr must be 100.00% removed. They are the A+ masters in the sharpening community and always end up with hair-whittling edges.
 
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I know what you are talking about.
The knife is sharp and the apex looks good but it feels a bit off on an upward thumb pass and sometimes I can’t detect it by feel.

When I get a knife to this point usually super ultra light passes on a 5k+ stone or with some steels very light stropping with diamond spray on basswood.

Every knife is different and some hold a burr that can be very difficult to get rid of.
A steady hand, light pressure, and good lighting can make it a little easier.
 
Have you tried the "fold over" technique to remove your initial burr? Part of the issue here is that you seem to be creating a burr with a high grit ceramic stone. Both of which are "bad" for creating tough burrs. Perhaps creating the burr at a lower grit level, then using the fold over technique, and finally polishing on higher grit stones without creating a burr. Maybe that would help?

Here's where I learned the fold over technique from our own member here, bluntcut:


Brian.
 
I don't worry anymore about detecting burrs visually, UNLESS they're just so obvious they can't be ignored by sight. My fail-safe test for burrs is in the cutting of fine, thin paper. The less burr that remains at the edge, the more effortless a push-cut will be and the less applied force behind the blade will be needed to initiate and sustain the cut. No snags or slips at all, and the blade just 'falls into' the paper under it's own weight, ideally. If the edge does this repeatedly and consistently, then I know for certain there are no remaining issues at the edge. Occasionally, on the first cut or two, I'll feel a little snag or slip, which then disappears on subsequent cuts (tells me the burr was so fine, it stripped away in the cutting). Any reflected light that might be seen coming off an edge always comes with a slip or snag that I'll notice immediately in cutting fine paper otherwise. So, I don't rely on the visual indicators by themselves, and instead trust in what the cutting is telling me. That's never failed me. It's a good thing for me personally, because my eyes have aged, and they weren't all that acutely focused to begin with, since I was in grade school about 5 decades ago.

Especially coming off ceramic hones, even very, very fine burrs seem impossible to ignore. They move around a lot, creating weird behaviors in my cutting tests of fine paper. I periodically re-visit using ceramic hones to touch up my edges. And with some less burr-prone steels, they're fine. But I keep noticing, over and over, the uniquely quirky behavior of more ductile steels coming off a ceramic hone in particular. That always makes me shy away from ceramics, in favor of something better capable of cleanly refining the edge on these steels.
 
Good discussion, seems we're all on the same page regarding this advanced topic. It is debatable which test is best to check for sharpening progress and remaining micro burrs. I slice up 1 sheet of phonebook paper at the very last as confirmation, sure; that is as long as i have the paper around me. When i am at a friend's place and want to get a full picture of his edge's condition, then my keychain AAA flashlight delivers all that info within seconds. I would look at the entire edge at once from 3 different angles (1x 'from above', 2x 'from behind') and would form a full 3-D picture of the entire apex line in my mind; and i'd confirm the burr existence with my thumb. Slicing up his phonebook paper would give me only a rough (and indirect) picture, because only the burrs (and not the rounded spots) would catch the paper fibers. In broad daylight the 3-angles flashlight trick can fail because of lack of lighting contrast and the sun brightness's blinding effect; the trick is best performed when the eyes are relaxed, wide open, and the background is dark, non-blinding. I like the flashlight trick a lot, it gives me fast a more complete and accurate picture of edge's condition and my sharpening progress. But we can all agree that thumbing the edge should always be included in the test either way. No eyes, flashlight, phonebook paper needed, the thumb tells us right away if there is any kind of burr wire edge left.

Sometimes i mistook the thumb feeling of a micro burr wire edge as indicator of a scary sharp apex. Not without reason, because a micro burr wire edge does have a cutting effect (similar to a toothy edge i guess) and grabs and cuts into tomato skin no problem.

But whoever is obsessed with edges would want the maximum, i.e. a clean unrounded apex, absolutely free from micro burrs. Ductile steels are the worst, stropping them can actually raise a micro (or even macro) burr, i've experienced it; it was an eye-opening, transformative experience tbh.

B bgentry Thanks for your thoughts and the @bluntcut video. My deburring repertoire includes all from his video and then some. Depending on the situation and the steel, it is my guideline to avoid creating any kind of burr in the first place. Avoiding creating a burr on higher grit ceramic stones is wishful thinking. Take an Endura 4 VG-10 OOTB (out of the box). It is scary sharp and 100% burr-free. Then do alternating strokes on the Sharpmaker with 204UF rods for a minute. This creates an "unvisible" micro burr wire edge, which may or may not grow beyond a size limit (depending on the grinding pressure) and which then gets flipped from side to side with each alternating stroke. Removing that micro wire edge is challenging. You believe that it is a tougher burr because it got created on a higher grit ceramic stone. This might/might not be true. Of course a burr created on a lower grit stone is automatically a macro burr, we can agree. And breaking off a macro burr is as easy as alternating sides of your balancing strokes. If you grind with high pressure, a higher grit ceramic stone can create a macro burr no problem. Of course we don't want to create any kind of burr on higher grit stones let alone strops. But the Endura example is a good one: it would be unacceptable to maintain a perfectly sharp edge with a 180grit water stone, there's no need to go back that far down for touch-ups. For touch-ups you'd use the Spyderco UF (with little pressure, of course) or a strop or both; and depending on how uncareful/unskilled you perform the touch-up, the edge will end up with a micro burr wire edge!

How to avoid or remove a super-persistent micro burr would be a whole other topic, and actually could not be really explained or described in detail. There are certain concrete practical things which can't be taught in text or video (like the experience of hitting a ping pong backhand top spin stroke in pro quality or striking a musical note on the violin in pro quality). This is why i focused in the op on the topic of "we were wrong… with the flashlight trick using 1 view angle only".

The past 2 years i wasn't aware of invisible tough micro burr wire edges. My original flashlight trick didn't make them visible, and my edges were scary sharp. After slicing up 1 phonebook paper very cleanly like nothing i did sometimes wonder why a few micro paper fibres were spread along some spots on the apex but not along the full apex line. I didn't care because the knife had passed the cut test with flying colors.

Now, after correcting the flashlight trick, i have gained a fuller perspective on the burr topic (micro burr detection, existence and creation of micro burr wire edge, accept or not accept the challenges of micro burr removal). For users who are serious with their stropping sequence it's not necessary to distinguish between macro and micro, i get that. Micro burrs are also not a topic after the PTS method on a guided system. Strops are indeed imho the best way to literally remove the micro burr wire edge. But it is imho still a helpful concept in one's mind when progressing through the sharpening steps: typical deburring efforts on a stone (balancing strokes, edge leading or edge trailing, doesn't matter!, and no matter the stone grit number) will take care of the macro burr only, and whatever burr wire is left is obviously very very persistent (because it is so small and can't be broken off). That's what we simply call the micro burr. With that name in mind, special techniques (like "folding over" and or shearing off with dedicated stones) plus serious stropping efforts are then needed to take care of that unvisible burr. And with acute ductile steel geometries it is practically impossible to remove the micro burr, unless you strop the edge from either blade side simultaneously lol (double paper wheel).
 
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To amplify what I was getting at earlier, I initially feel with my fingertips for the first BIG burr created in the beginning step of sharpening on a coarse stone, just to verify I've fully apexed. After that, as I'm starting to clean up the burr & refine, I'll sort of bridge that with some test-cutting of paper, doing a little bit of both (by feel with fingertips, and by cutting).

There'll always come a point where the tactile indication of a burr starts to fade and becomes inconclusive by feel alone. That's when I'll start doing frequent test-cutting of paper after every few passes (3-5) on the stone. Initially, I expect to see or feel some snagging and/or slipping when I'm sure there's still some burr left. But as I refine & clean it up, I'll start to notice improvement in how easily or how smoothly the edge cuts, both in how it initially bites the edge of the paper and also how smoothly it slices through the paper. As I progress further, I'll start testing how lightly I can hold the knife and still cut the paper easily. I do this by gripping the end of the handle between thumb & forefinger, which minimizes how much force I exert in the cut. First in slicing cuts, then as I refine & thin the edge further, I might start noticing improvent in push-cutting, holding the handle the same way and letting the blade essentially fall through the paper.

I also look for how dead-straight each cut is, going into the paper. If I see the cut deflecting or curving one way or the other, even slightly, I assume there's still a hint of leaning burr left at the edge, which tends to 'steer' the cut in the direction the burr's leaning. This is where using something like a smooth kitchen steel does a great job removing any weakened burr fragments and also aligns the edge more or less dead-straight, and produces an extremely sharp edge that dives in a straight line through the paper with almost no effort. If I get to that point and see the same, repeatable behavior along the full length of the cutting edge, that's when I'm ready to call it 'done'. I don't necessarily take it that far with every knife or every sharpening task. But it's very comforting to see it behave as such when it does happen. :)
 
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So do check with your thumb
if the op gets 5 Likes, i'll add pictures
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Yes I would like a photo or more text to clarify this. Is it like this . . . lightly pushing the blade away from me down toward the tip of my thumb.
See photo here at this LINK > > >

This what you mean ?

This does work for me for testing for micro bur because the side that catches less aggressively has the micro bur bent away from that side. I find when we are talking Micro . . . bur it is so flexible a breath can bend it over . . . well maybe not that flexible but nearly. On the order of extra thin foil.

However when I get a base of spine disturbing bite on my nail with the lightest touch ON BOTH SIDES OF THE EDGE that feels equal then the edge is done (bur is gone). This is some where around easy and multiple curls off a single hair in my arm or tree topping. The former is what I look for and is "good enough" for me.

NOW all that said :
I appreciate the skill to hand sharpen.
I cheat and use an Edge Pro Apex though I can get stuff "sharp" by hand.
One thing I want to emphasize when we are talking hand sharpening, MICRO burs, final strokes and deburing is . . .

when a person is doing one stroke per side back and forth to put on the final edge and debur the edge . . . free hand now . . . how do you KNOW you are on the edge all the way along the stroke ? ? ? ?
I think it is ENTIRELY possible that one can take a stroke on one side thinking, feeling, working up all the mojo and kroompst in one's little body to be sure that one is right on the edge . . . and not ACTUALLY be on the edge
then
flip the knife over and do the same on the other side AND ACTUALLY BE on the very edge and so doing exacerbate the problem by actually increasing the bur.

With a jig one is sure one is on the edge on both sides with each stroke then it is just down to pressure on the stone to keep the bur , or deburing action, balanced.

Again I say sticking up one's thumb and sticking out one's tung are not viable methods for precision sharpening but a mechanical guide is.

now
all that banged out . . . for taking off the micro bur while hand sharpening we are down to squishy strops to take up the slack for the varying angles, though they may only be fractions of a degree (((( on a good day )))).

Got a micro bur ? Free hand sharpening ? Then use Strop.

As far as the bur

You wouldn't expect or believe it, but most likely there is still a micro burr at the apex.
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I have a little desk lamp we use as a light near the phone and I tilt the edge under it while wearing powerful magnification and i can see the micro bur and or micro fragments left on the edge from deburing. I tilt the blade back and forth while held horizontally with the light behind the knife / edge as you describe.

Typically micro burr is extremely persistent and is even raised by balancing strokes on Spyderco UF
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Yes but I would emphasize : With Some Steel Alloys.
There are others that respond very satisfactorily to the Spyderco Ultra Fine stone and actually are easily debured or do not form a bur worth mentioning while using the UF . M4 and HAP-40 for two examples.

PS : I had your thread in mind while sharpening my HAP-40 Delica. I used sharpy on the first coarse stone and my stop colar from then on for stone thickness compensation on the Edge Pro Apex.
I rasied a slight bur on the first stone. Ignored it completely from then on. I just mindlessly went through a few stones from there up to Shapton Glass 4000.

After the 4,000 I looked at the edge as we discussed (using my high mag jeweler's visor). The bur was completly gone. The edge was multiple curl hair whitliting.

Mircro bur emurgency averted by sharpeing REAL tool steel with a decent heat treat.

Hahaha I asked the guys here how to take the micro bur off that funny stainless stuff after much fooling around with "techniques" and they said strop it on your dirty jeans what does it matter.

We are all joking about it and it's fun. Honestly something like a Norton 8,000 water stone or my new Gritomatic Suehiro G8 Silicon Carbide Sharpening Stone do wonders but not easy.

Good edges start and end with good steel.
 
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I almost never use the Spyderco UF, though I have a full sized 8x2 stone in that grit that I found on an incredible deal at the flea market. These days I tend more towards a very sharp, cleanly apexed edge, at no more than about 600-ish grit, like the Spyderco medium. Touching up on a 3 micron stone like the UF isn't something I ever do.

If a factory edge is "perfectly clean" according to your standards, it might be worth emulating their finishing technique to get rid of everything. Namely a cotton buffing wheel. I believe that's what most (but not all) knife manufacturers use to remove the burr after the edge is ground in on a wheel or belt sander. If you aren't into power tools, even for finishing (and I would understand that), maybe something similar. Like a denim strop? Perhaps loaded with very fine compound like 3 micron green stuff, or 1 micron (or sub micron) diamond spray. I would bet that 1 micron or 0.5 micron diamond spray on a flexible backing would eliminate all of that micro burr coming off of the Spyderco UF (which is ~ 3 micron itself). Hell, that kind of strop might actually replace touching up on the UF, depending upon the condition of the edge.

Brian.
 
today i taught myself yet another technique for removing persistent micro burr. I'll have to test it more and on other knives but it seems promising so far, here we go:

edge-trailing, almost edge-following!, strokes at a sharp 90° stone edge. fast strokes with little pressure. the edge-trailing direction reduces the chances that fresh new micro burr wire edge is formed.

edge-leading, almost edge-following!, strokes are more common for deburring efforts because of the shearing effect but it can be, if you're not skillful, also counterproductive when it creates its own microburr (at the micro bevel). so one has to balance the pressure and technique perfectly, which requires lotta practice, experience and frustration resilience.

Even with the improved flashlight trick micro burr wire edge can still remain invisible to the naked eye (i don't use a loupe because i use a flashlight instead), yet it can be felt by the thumb.

So one could say that the thumb is the best method for detecting bevel sections with any kind of burr (macro or micro). True. But the thumb doesn't tell you about dull sections and their exact location and extent. You'll still need the flashlight (or headlamp) for that. The light tells you also about the size of the micro burr, which can be interesting if not helpful.

I'm not claiming that it is necessary to remove the micro burr wire edge for an edge to be scary sharp, but i wasn't really aware of its existence because i never looked for it (flashlight trick applied wrong my bad). now i look for it even during my stropping efforts and the difficulty of getting 99% rid of it manually drives me mad:mad:

i have a dremel tool but not a cotton wheel:confused:
 
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The article linked by Garry3 is really informative, although -- rightly or wrongly -- I question some of the assertions. Regardless, it's a great article for improving your thought processes about de-burring.

My system is simple: I use power grinders only to set the initial bevel. After that, I use only stones (mostly diamonds) so that I don't damage the apex.

I use the Wicked Edge, and so I tend to scrub (edge leading alternating with edge trailing) until I reach the apex and the burr starts to form. After that, I use only edge-leading strokes.

I de-burr regularly with very short, almost chopping strokes (no more than a quarter inch long). Edge-leading strokes push up the burr force it to lean over the opposite side. With the same angle of attack, the hone will cleanly cut off the burr. If you keep the stroke short and light, the new burr that forms on the opposite side will be kept very small. By regularly cutting off the burr, I can keep the burr root small and narrow.

I do this with each stone in the progression, using lighter and lighter strokes with the finer and finer grits.

When done, and before stropping, the apex should be clean and as burr-free as my skills allow. The strop just refines the edge with a few light, edge-trailing strokes.
 
Twindog said:
The article linked by Garry3 is really informative, although -- rightly or wrongly -- I question some of the assertions. Regardless, it's a great article for improving your thought processes about de-burring.

My system is simple: I use power grinders only to set the initial bevel. After that, I use only stones (mostly diamonds) so that I don't damage the apex.

I use the Wicked Edge, and so I tend to scrub (edge leading alternating with edge trailing) until I reach the apex and the burr starts to form. After that, I use only edge-leading strokes.

I de-burr regularly with very short, almost chopping strokes (no more than a quarter inch long). Edge-leading strokes push up the burr force it to lean over the opposite side. With the same angle of attack, the hone will cleanly cut off the burr. If you keep the stroke short and light, the new burr that forms on the opposite side will be kept very small. By regularly cutting off the burr, I can keep the burr root small and narrow.

I do this with each stone in the progression, using lighter and lighter strokes with the finer and finer grits.

When done, and before stropping, the apex should be clean and as burr-free as my skills allow. The strop just refines the edge with a few light, edge-trailing strokes.
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I think it's good to question everything you read. Nothing like first hand knowledge and experience by doing. :thumbsup:
 
In order of speed and convenience:

Three finger sticky
Thumb/fingerpad grind from spine off of edge - compare side to side feel
Over head lighting, hold blade level with eye, edge pointing straight down, pivot back and forth, check both sides
Same as above with loupe

For quick removal I just double the angle (or higher) and make a few light leading passes, follow with a few passes at the original angle. Microbeveling w/ light touch also does a good job of final burr removal.

If you don't see one or feel one, there isn't one there. I've cross referenced this using 1000x microscope and it holds true.
 
Michael Christy just published a full sharpening video (which is rare) of S110V and talks about the burr at higher grit levels and burr removal, not using freaky movements like everyone else. His sharpening technique is unconventional (i adopted it) but the success proves him right:
 
I'll catch the video tomorrow when I have a bit more time, thanks for the link!

My personal experience is that burr removal on high RC, high carbide steels is very easy compared to regular budget stuff. Aus8, 420HC, the Sandvik series all can be a lot more stubborn than anything with a RC greater than 60. Of most of the high carbide steels only D2 and 154cm can really give the run around, and then only if it isn't very high Rockwell.
 
HeavyHanded said:
I'll catch the video tomorrow when I have a bit more time, thanks for the link!

My personal experience is that burr removal on high RC, high carbide steels is very easy compared to regular budget stuff. Aus8, 420HC, the Sandvik series all can be a lot more stubborn than anything with a RC greater than 60. Of most of the high carbide steels only D2 and 154cm can really give the run around, and then only if it isn't very high Rockwell.
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This.^

I've also noticed VG-10 and ATS-34 (similar to 154CM) can be tedious as well. With VG-10, most issues come with hardness at mediocre levels for this steel (think Spyderco), but it's less of an issue at HRC 60 or better.

The few knives I have in ATS-34 have all been the champions of tenacious burrs, even at relatively high hardness of HRC 60 or slightly higher. I have to work harder at cleaning those up, than with any other. The burrs are amazingly tough on this steel, both very strong and very ductile. They have to be gradually abraded away, as they just don't break off by bending back & forth, as with most other steels.
 
HeavyHanded said:
For quick removal I just double the angle (or higher) and make a few light leading passes, follow with a few passes at the original angle. Microbeveling w/ light touch also does a good job of final burr removal.
Click to expand...

razor-edge-knives said:
Same for me, esp. The microbevel cleanup, whisper light edge leading passes and works amazing.
Click to expand...

Do these burr removal methods apply to toothy edges as well as smooth edges?
And, do you remove burrs with the same grit size you made them with or remove them with a higher grit?

Thank you....
 
MtnHawk1 said:
Do these burr removal methods apply to toothy edges as well as smooth edges?
And, do you remove burrs with the same grit size you made them with or remove them with a higher grit?

Thank you....
Click to expand...

On high RC, high carbide steels - not just high VC steel, stuff like ZDP as well I try to reset the bevel with nothing more aggressive than a coarse DMT/Ultrasharp/DMD, whatever diamond plate.

Then I double the angle to remove the burr - this can often be done with a single pass or no more than a few partial passes. The steel being so hard, the burr small, the attachment point brittle, they tend to brush right off. One of the nicest things about these steels is they are extremely unlikely to form wire edges.

Increase the angle about 2° and make about 5-10 very light microbevel passes on an EF or equivalent. This should thin the apex width while making the actual cutting edge a bit less acute, and still leave some of the tooth from the rougher stone. This being my default edge finish for a lot of these steels. I might make a single pass on a hard strop just to help QC for burrs, but it is pretty rare any will survive the microbevel.

With a lower RC steel is much the same, I deburr on the same stone, microbevel on a much finer one. if the blade is convex or scandi, or a woodworking tool I run a full progression deburring as I go, and only microbevel the woodworking tools, and then on an 8 or 10k
 
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