Wire edge that won't go away

[Bufford]

When I sharpen, the simplest method to get rid of that wire edge is usually only a few gentle strokes on a good chef's knife steel. Wire edges can be reduced by using good stones that are sharp, not worn. Keep your stones clean to keep them sharp. When using the belt grinder use only fresh belts. For the most part a 120 grit will set up the primary edges. Then I use a 320 grit to finish up the primary edge. I use the stone to work up the secondary edge and by then its pretty sharp and most of that wire edge is gone. To finish up I use a good steel and give the knife a few passes to 'set the edge' and remove any wire edge. The knives are razor sharp and ready for use.

 

[yuzuha]

I'll second Cliff's comment about M2... great steel for sharpening. Using a slurry on waterstones, I don't even get a burr.... just the action of the slurry is enough to keep it ground off. Unlike my BG-42 SOG mini autoclip that seems to want to sprout sheets of foil from the edge (that is the only knife I've had to resort to extreme deburring with, and that was when I was seeing just how thin an edge it could take and still hold up).

 

[HoB]

I agree, having a slurry on the waterstones, seems to break up most of the burr. Whenever I transition from what I consider a medium stone (up to roughly 1500 grit) to a fine stone, I make sure I carry as small a burr with me as I can. I use Jeff Clarks technique of raising the angle on the medium stone. Once I am done with a 700-1500 grit I want the edge to shave (it may still be rough but it must shave). I find that trying to remove a large and floppy burr on a stone that is too fine is fairly difficult....possible, but if you don't pay attention and use the right amount of pressure you are just going to push it around. As a general guideline I find it best to remove the burr on the same grit or maybe on step finer as the grit that created the burr.

A totally agree with STR here. I hate burrs. I rather take a steel with high abrasion resistance on which I have to work longer, that burrs little, that one with low abrasion resistance that burrs badly. I never had problems with S30V though. As a matter of fact I prefere S30V to 420HC. With the latter it is easy to rip in an edge but burr removal I find very difficult. S30V is a b!+c$ to reprofile, but I never had problems with excessive burr.

If all fails I use Yuzuha's method. I may even use a medium stone and simply pull the entire edge off with one or two very light strokes. Sometimes it is easy to start with a clean slate (a flat but clean edge) than dealing with a bad burr. The light strokes will ensure that you don't have to start completely from scratch...you don't have to reprofile, you just reestablish the edge.

 

[Dog of War]

Using a fine (but not ultra-fine) stone, hone very lightly single strokes at 45 degrees. Do a single stroke on the right side then a single stroke on the left side. Use virtually no pressure. Alternate left-side/right-side single strokes. Do this for a total of 3 to 5 strokes on each side total.

This makes a lot of sense. I've always suspected that some of the traditional ways of removing a burr actually tear or break loose good steel, or otherwise leave you with a good deal more work than's really necessary to get back to sharp. But this way you're cleaning off the burr and leaving an even edge that's just a little more obtuse. If I understand correctly, you then simply remove the shoulders on the edge which shouldn't tend to produce another burr, and you're ready for finish sharpening.

Of course I try to avoid knives that tend to form bad wire edges ..... but when I can't, I sharpen them on a rubber sanding block with emery paper, which for some reason doesn't tend to produce a wire edge.

BTW too, despite my general disappointment with S30V, wire edges have never been a problem. Brittle, more often.

 

[Jeff Clark]

Responding to Cliff's questions:
"Have you tried finer belts and/or a buffer?"
--I have up to a 600 grit belt, but a worn 400 grit belt seems to do as well. I was in a hurry.

"Are all the knives large slicers?"
--No, only a few were large slicers. I have a lot of poorly trained amateurs using these knives and at least one of them went to the hospital when I routinely brought 10-inch knives. I brought two of the CK-90's and a 10" Dexter chef's knife for use by selected parties. Often there are 6 or 8 people working on a single table at a time and longer knives are a hazard. On the other hand many people will incorrectly use a paring knife if I give them a chance. I tend to provide 6- or 7-inch cutting-board-compatible knives to the people who are preparing fruits and vegetables. This tends to force them to use the cutting board since the knives are too long for paring. People who are boning and dicing chicken also need smaller boning or paring knives. I give them knives for the cutting board and short-narrow knives for boning. The CK-90's are nominally slicing knives, but they work extremely well as chef's knives. The only issue is that the cutting edge is a little straight for my taste. They have enough length so that they can be used for chopping as well as press cutting and slicing. I brought those out since I assumed that was what a chef would prefer. He immediately went for the knife that I expected.

I mostly provide knives in the same class as a MAC UK-60:

Although a finer finish on the edge might make some sense for use dicing vegetables the Spyderco "medium" ceramic finish is plenty fine enough. One of the ways that I have cut down on injuries in the kitchen is by giving a lecture on knife use to volunteers. I warn them that knives aren't dangerous, but high presure and round objects with tough skin are dangerous. If you push hard on an apple to penetrate the skin it can roll on you or the blade can suddenly pop through the skin and out the other side of the apple. I have them put food on the cutting board and let the sharpness of the knife do the work. If they meet any significant resistance while push-cutting they are supposed to resort to a gentle slicing technique rather than extra pressure on the blade. If I leave the blade finish just slightly rough their slicing technique is quickly rewarded. I have managed to get through several sessions without any cut volunteers with this approach.

 

[Cliff Stamp]

I have up to a 600 grit belt, but a worn 400 grit belt seems to do as well. I was in a hurry.

I was wondering why you don't just finish on power equipment completely?

Although a finer finish on the edge might make some sense for use dicing vegetables the Spyderco "medium" ceramic finish is plenty fine enough.

That was what I was thinking of for many knives. I find that really rough for peeling potatos and such, but for most people the knives you give them are going to be vastly sharper than anything they have seen anyway. Hell of a time sharpening the knives by the way, way faster than I would take.

I agree, having a slurry on the waterstones, seems to break up most of the burr.

I think it may be static related. I have checked under magnifiation on dry diamonds and the edge is full of debris, if you try to just wipe it on something dry it just piles up most debris, lint from cloth for example. On the other hand the same edge from a waterstone is clean after a quick wipe on a paper towel. Water on the diamond stones seems an obvious point of comparison on reflection and or maybe using a fine slurry with them.

-Cliff

 

[yuzuha]

No, I don't mean swarf, I mean waterstone slurry/mud on 3000 grit - 10,000 grit stones...it is a paste formed from the waterstone that sort of acts like valve grinding compound and has a mild abrasive action (controlled by viscosity) on the burr as it crawls over the edge to the top of the blade.

 

[Jeff Clark]

Cliff,
I finish with manual hones to help remove burrs and weak edge material and to get a finer edge. My manual finish step takes less than 30 seconds per knife when I am doing them in big batches. I spend about 4 or 5 times as long on the belt sander. If I ran out of time I could just leave my belt sander edge, but I have a reputation to maintain. The regular members of my crew are used to my manually finished edges (I've been bringing my knives along for over 5 years) and will set aside less sharp knives as defective. Sometimes they reject sharp knives if they don't have the extra-thin edge profile that I normally use.

Regarding static and diamond hones: When I am doing my quick sharpening I keep a terrycloth rag handy to wipe off my deburring diamond plate. When I am trying to improve the edge on an extra hard steel I sometimes use the same hone under flowing tap water. That flushes the surface and prevents any static build up. I think that it helps, but I haven't noticed a striking improvement. Sometimes I lean the hone along a rod in my Sharpmaker fixture to get a more precise bevel. This seems to work as well as running under tap water. It is possible that some of the honing debris falls off in this orientation.

 

[orthogonal1]

That's interesting - a bit of confirmation that my change from water/oil stones to dry ceramic/diamond may have affected how sharp (and how easily I get that sharpness) my knives get.

Variables, so many affects.

 

[Cliff Stamp]

If I ran out of time I could just leave my belt sander edge ...

Yes, I wasn't thinking of this but more of using belts of similar grit to the stones, or a buffer with suitable abrasive. However 30 s or so on the stones is really fast, it would be hard to beat that significantly with a finer belt and/or buffer.

[upright]

It is possible that some of the honing debris falls off in this orientation.

On a related note, I have heard from many who sharpen chisels that you are supposed to slap them off your hands periodically. This may minimize the burr by knocking off debris.

... a paste formed from the waterstone that sort of acts like valve grinding compound and has a mild abrasive action (controlled by viscosity) on the burr as it crawls over the edge to the top of the blade.

I would wonder how much abrasion this can induce on top of the blade because in order for the grit to cut through the metal it has to be able to resist the contact force necessary to allow it to cut. It would be interesting to compare the finish when used traditionally as well as under flowing water and see how they differed.

-Cliff

 

[yuzuha]

I would wonder how much abrasion this can induce on top of the blade because in order for the grit to cut through the metal it has to be able to resist the contact force necessary to allow it to cut. It would be interesting to compare the finish when used traditionally as well as under flowing water and see how they differed.

-Cliff

Well, it would be greatly exaggerated but it is sort of like hacking into a pile of sharp sand. It isn't a cure-all, it only helps. On steel that forms small burrs it is often enough to prevent its formation. On steel that burrs more, it often eats away at the burr so it fragments and is easier to get off (and often just falls off in little pieces). On things like BG-42, it only fragments the foil a little... helps a bit but not a cure.

Under running water, waterstones act like an Arkansas stone or your diamond plates and leave a rougher but brighter finish. Rougher because the abrasive doesn't have time to shatter into smaller and smaller pieces (with the slurry, you are not only sharpening the blade, but crushing the loose abrasive grains). Under a microscope, the sans-slurry steel is full of nice neat little furrows like a plowed field, the sides of these furrows are all lined up and reflect light well so the finish looks brighter. With the slurry, the surface is smoother but looks more sand/bead blasted so it scatters light more randomly so may not look as shiny (some stones will actually make some stainless type steels look dark because the mud will collect in the tiny pits and not want to come out, which is why some stones are not recommended for stainless).

 

[Cliff Stamp]

Well, it would be greatly exaggerated but it is sort of like hacking into a pile of sharp sand.

I understand the point, but am skeptical of the extent. Consider for example the slurry just poured onto a knife would it scratch it up heavily? If it doesn't then it would seem unlikely that it is getting any abrasive action on top of the edge. My blades tend to get scratched from the slurry on the primary, but I will wipe it off roughly and thus the paper towel acts like sandpaper which I assume was what caused the abrasion.

Under running water, waterstones act like an Arkansas stone or your diamond plates and leave a rougher but brighter finish. Rougher because the abrasive doesn't have time to shatter into smaller and smaller pieces (with the slurry, you are not only sharpening the blade, but crushing the loose abrasive grains).

Yes this seems logical but this I would argue is due to the slurry trapped between the blade and the stone, essentially changing the grade of the stone, not the slurry riding up over the edge and honing the side of the bevel opposite to the stone.

Under a microscope, the sans-slurry steel is full of nice neat little furrows like a plowed field, the sides of these furrows are all lined up and reflect light well so the finish looks brighter. With the slurry, the surface is smoother but looks more sand/bead blasted so it scatters light more randomly ...

That is a rather interesting point and has applications for slicing aggression, can you see pictures of this online? Note in his book Lee has high mag shots of edges honed on waterstones (recombined and natural) and a oil stones and arkansas and they all show the same very uniform scratch patterns on the sides of the edge. He doesn't go into detail about how he used the stones, but he does discuss use of secondary conditioning stones for waterstones and mentions use of a slurry so I assume he wasn't rinsing constantly.

...the mud will collect in the tiny pits and not want to come out, which is why some stones are not recommended for stainless).

Is this a bond or grit type or size issue? Have you seen this experimentally?

-Cliff

 

[Jeff Clark]

Cliff,
I know that we've seen micrographs of waterstone edges on the forums here before that illustrate the sort of finish that yuzuha describes. It reminds me of the surface of a blanket layed loosely on a bed. I can't remember the specific thread.

 

[Cliff Stamp]

I wonder about the type of sharpening action, you can see a very difference finish with circular motions vs back and forth pulling for example, and looking at Lee's pictures all of the edges look the same on the sides in terms of structure of the scratch pattern.

-Cliff

 

[yuzuha]

I understand the point, but am skeptical of the extent. Consider for example the slurry just poured onto a knife would it scratch it up heavily?

Not really, with waterstones you use a nagura and start working up a slurry at about 3000 grit to form sort of a thick mud or paste, so "scratch it up" is a relative thing.

If it doesn't then it would seem unlikely that it is getting any abrasive action on top of the blade

The action on top the blade is mild, but then you are using polishing on the slurry, that gets to about the consistancy of modeling clay when throwing a pot on a potter's wheel, and flipping the blade.... and, in so doing, slicing through the mud. It is just a gradual wearing away at the edge that helps prevent burr formation and helps reduce any that have already formed.... sort of like a stroke grinds on the bottom and gently strops on the top at the same time.

Yes this seems logical but this I would argue is due to the slurry trapped between the blade and the stone, essentially changing the grade of the stone, not the slurry riding up over the edge and honing the side of the bevel opposite to the stone.

Yes, this happens too... the aoto blue stone is about 1,000 grit JIS but you can get a 3,000 grit polish from the mud if you let it collect, and the Kitayama 8,000 grit will produce a polish approaching that of a 12,000 grit stone.

That is a rather interesting point and has applications for slicing aggression, can you see pictures of this online? Note in his book Lee has high mag shots of edges honed on waterstones (recombined and natural) and a oil stones and arkansas and they all show the same very uniform scratch patterns on the sides of the edge. He doesn't go into detail about how he used the stones, but he does discuss use of secondary conditioning stones for waterstones and mentions use of a slurry so I assume he wasn't rinsing constantly.

I don't have a camera for my microscope ( one of these http://www.microscopesusa.com/Vision.html a 10x30 on a dual lamp stand with all the extra eyepieces and supplemental lenses so I can get various powers between 5x and 150x) or I would have posted a ton of pictures.... I have about 18 waterstones and when I was bored I'd polish up a knife or even a small block of steel just so I could see how different stones affected different steels. I really haven't searched for such pictures online, but I have seen a few here and there... not sure where though.

Well, I just found a comparison of a Norton 8k waterstone finish to 1 micron diamond on S30v http://cablespeed.com/~sgelliott/blade_testing/html/abrasive_choice.html
though the Norton 8,000 is a 3 micron abrasive and the pic doesn't show the matte surface I was talking about, but it does give the general idea.

 

[HoB]

Actually, if you look closely, you can even see how the slurry wraps around the edge if you have thick enough of a mud. It looks similar to a blade under pressure on a strop. Its like walking in sand. The sand wraps around your foot and while most of the pressure is underneath, there is a non-vanishing pressure at the "walls" of the foot print. As Yuzuha describes, its not a magic bullet but it helps.

 

[Cliff Stamp]

Yes, this happens too... the aoto blue stone is about 1,000 grit JIS but you can get a 3,000 grit polish from the mud if you let it collect, and the Kitayama 8,000 grit will produce a polish approaching that of a 12,000 grit stone.

I have some natural stones which form a much readily, it would be interesting to compare sharpness both clean and muddy.

Actually, if you look closely, you can even see how the slurry wraps around the edge if you have thick enough of a mud.

I don't debate that it is there or that it is contacting the blade, just the effect of the contact.

The sand wraps around your foot and while most of the pressure is underneath, there is a non-vanishing pressure at the "walls" of the foot print.

It has to be more than non-zero though, it has to be enough to resist the counter force of the cutting abrasive. Consider if this was the case and the slurry which rode over the bevel does act to cut off the burr, or at least minimize it. Would it also not be the case that it would induce a similar grinding action directly against the edge itself and be blunting the blade and prevent sharpening?

-Cliff

 

[t1mpani]

The best method I have found is to take the knife and cut into hard wood--I have a piece of scrap oak by my sharpening table that is relegated to this purpose. I do (as others have said) heel-to-toe draws with light pressure, as if I was trying to slice into a bread loaf. This seems to tear off the wire edge, and doesn't blunt or square the edge like doing it on a stone would. Generally, some additional sharpening will be required afterwards to finish off the steel that the wire edge was covering, but it goes pretty quick.

 

[HoB]

Would it also not be the case that it would induce a similar grinding action directly against the edge itself and be blunting the blade and prevent sharpening?

-Cliff

Well, that is exactly what I am thinking and one of the reasons why I am using a trailing stroke on very soft stones.

 

[HoB]

The best method I have found is to take the knife and cut into hard wood--I have a piece of scrap oak by my sharpening table that is relegated to this purpose. I do (as others have said) heel-to-toe draws with light pressure, as if I was trying to slice into a bread loaf. This seems to tear off the wire edge, and doesn't blunt or square the edge like doing it on a stone would. Generally, some additional sharpening will be required afterwards to finish off the steel that the wire edge was covering, but it goes pretty quick.

That is precisely the technique that Murray Carter suggests in his video. Personally, this is one of the things were I deviate from Mr. Carter's technique. I had some burrs that I simply couldn't get rid off this way but that yielded with Jeff Clarks technique (raising the angle).