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 Post subject: Re: Starting a new edge?
PostPosted: Sat Feb 15, 2014 4:58 pm 
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Yeah, I usually only reset the edge if I need to tweak the edge profile (like if I started to get a recurve or birds beak at the tip, or I want to remove some belly) or if I went to a zero edge when doing blade thinning. Some people, especially if they are new to sharpening, over sharpen a knife in spots like the heel and tip and need to fix the profile or like you said, use the flattened edge as a reference when sharpening. I usually go with a burr to know I am at or fairly close to the edge on the coarsest stone I am using and then remove it and then consciously let up on the pressure and try to not generate a burr. I know it will happen, so I try to not let it happen! I know I am at the edge or close to it and its more of a mental thing I guess trying to get the edge w/o forming a big honking burr that will undo a good bit of the work I just did if I rip it off! I try to do a non forceful burr removal (I shudder running a blade through cork blocks!) and the Japanese natural stones I often use at the higher grits form very tiny burrs and the mud/slurry helps remove the burrs as well. I prefer to abrade the burr off rather than pull it through a cork block for most steels. Usually a few light passes on a strop attached to a block of wood and it's good to go! Some steels really like to hold on to the burr/wire edge and need more aggressive means to fully remove the burr, but this is the exception for the steels I normally use rather than the rule. I hate VG-10 for this reason and prefer to work with carbon steels or G3/AEB-L. M390 is a PITA to sharpen/deburr, too. I find that if I am really paying attention and using the J nats, I can often progress through a few finer grit stones before having to remove the burr because it's not that noticeable. Sometimes the burr is barely detectable, but I notice a difference before and after removing the burr. I strive to get no burr, but I'm not quite there yet! So I got for the smallest burr possible and then make sure to remove it fully, then retweak the edge a hair more to refine that edge or bring some more tooth to the edge.

Different stones react to different knives. I sharpened up a Takeda gyuto in AS core steel and went with one of my harder than normal Aoto stones as the last stone for the edge since the customer loves the toothiness to the edge. I could feel teeny bit of a burr when I came off the stone, so I stropped on leather 3 passes per side and then like 2 light stropping passes on the stone per side. Wickedly sharp edge! Next, I took a Blue #2 Kono Fujiyama and used the same San Aoto stone and method on that, and the edge wasn't as clean and precise, even though it was as thin or thinner behind the edge; the burr was a bit different, too. Same with a Tanaka Sekiso that I sharpened; I had to go to a level 3 Hakka stone and then a Hideriyami and similar progression to get the same type of edge on the blue #2 that I got on the AS steel.


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 Post subject: Re: Starting a new edge?
PostPosted: Sat Feb 15, 2014 8:48 pm 

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Yeah Taz...My Shun VG10...I mean I can chase the burr all night and even after a few bottles of strong ale I still see the burr.

To paraphrase Ken Scwhartz "The best way to remove burr is not get one in the first place." I think he is trying to suggest that removing it entirely while working on sharpening is the best method, and it seems to be happening more and more when I practice. Corks are a great way to slip and get cut...If the knife is sharp and a small burr is present it could grab the cork right out of the hands of the clumbsy user and cause serious bodily injury :)


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 Post subject: Re: Starting a new edge?
PostPosted: Sat Feb 15, 2014 10:29 pm 
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Ken's idea is to grind just enough so you don't generate a burr. A burr is formed when you grind the edge until you reach the other side and keep going. Basically you are overginding one side and then overgrinding it again when you flip the burr to the other side. His idea is grind it half way with no real burr and then flip the knife and grind the other side to meet the first.

It's tricky to do and I don't really have the patience to do it freehand, but the idea is if you grind a little on each side and observe the edge under magnification you can manage to make both the edges meet without "overgrinding" and generating a burr. Using something like the wicked edge where you grind each side with alternating strokes is a way you can get a burr-less edge and this is the easiest way to do what Ken suggests.

I'm quite sure he could explain it better than I. :lol:



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 Post subject: Re: Starting a new edge?
PostPosted: Sat Feb 15, 2014 10:36 pm 
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chefknivestogo wrote:Using something like the wicked edge where you grind each side with alternating strokes is a way you can get a burr-less edge and this is the easiest way to do what Ken suggests.


...or, you can just sharpen using edge leading strokes...to avoid the burr.



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 Post subject: Re: Starting a new edge?
PostPosted: Sat Feb 15, 2014 11:31 pm 

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It's impossible to not generate a burr it's just part of sharpening. For a edge to become sharp the slopes must intersect at the apex and when this happens a burr will form. Burrs will even form before the apex is reached so if your not forming a burr then you are either not sharpening correctly or simply don't notice them.


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 Post subject: Re: Starting a new edge?
PostPosted: Sun Feb 16, 2014 12:33 am 
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With edge leading strokes, on an 8k stone, there is little to no metal pushed over the opposite side of the apex of the edge, especially if done gently.

Might have been better to say......"or, you can just touch the edge up using edge leading strokes...to avoid (having to look for and remove) the burr, and or waste time and metal."

Burr assessment is unnecessary for almost anything other than major edge setting at lower grits. ie: repair, etc.

I've looked many, many times at 300x magnification.

However, for the topic of this thread, starting a new edge, burr assessment might be applicable, but even then finding a burr on a new Japanese knife with a super fine edge
seems completely unnecessary.



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 Post subject: Re: Starting a new edge?
PostPosted: Sun Feb 16, 2014 3:56 am 

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Cool. Now I have a new goal. Sharpening without forming a burr. I am so glad I bought the usb microscope.


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 Post subject: Re: Starting a new edge?
PostPosted: Sun Feb 16, 2014 5:31 am 
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Jason B. wrote:It's impossible to not generate a burr it's just part of sharpening. For a edge to become sharp the slopes must intersect at the apex and when this happens a burr will form. Burrs will even form before the apex is reached so if your not forming a burr then you are either not sharpening correctly or simply don't notice them.

Totally agree Jason. I try to keep the burr as small as possible but even across the entire edge. I think that those that believe that they are not generating a burr are just abrading it before they notice it or check for it.



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 Post subject: Re: Starting a new edge?
PostPosted: Sun Feb 16, 2014 7:33 am 
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Well Mark's comments about my approach are pretty accurate - Thanks! Is is worth adding a few comments about not producing burr.

Edge leading vs trailing. You can produce burr going in BOTH directions. This is more obvious with power grinding on a belt grinder. My Burr King unit goes in an edge leading direction. I can certainly produce burr with this unit. My Coote grinder goes both directions and you can produce burr edge leading and trailing. WHY?

Burr is produced when one goes past the point of creating a union of the two sides - in either direction. It's not so much that you are pushing the metal over the edge but that you are pushing the metal to a point after the two sides meet where there is no support. If you want to see a similar phenomena in nature think of ocean waves. A swell has no foam. A large surf wave reaches a point where the water no longer has laminar flow and becomes turbulent flow. Think of this disorganized flow and burr formation (which is fatigued metal) as somewhat similar phenomena. On a belt grinder at full speed, you easily blow past this point of union. By hand you can sneak up to the point of burr formation. With higher pressure this occurs in fewer strokes and it is easy to blow past it. With lighter pressure you can hit the point where it is just about to 'burr'. On coarser grits you can approach this to within a fraction of a stroke - yes you can :)

HOW? The trick is to develop a sense of perceiving a SUDDEN INCREASE IN SHARPNESS. Right before the two sides meet the sharpness goes WAY UP. Perceiving this is a skill worth developing. It is worth testing along the blade to get all of the blade there close to simultaneously.

Using burr formation is a crutch. For a beginner sharpener it is a necessary one - at least you are in the ball park. But it is a skill once learned to unlearn.

If you want to understand this crutch and getting around it, try sharpening a ceramic blade where you don't have burr formation as a crutch to use in your technique. Also try honing a razor and dealing with removing burr and you will see why razor honers don't rely on burr formation.

To some extent 'no burr' is an ideal and not always practical. When removing chips, especially big ones, you do go past the point of union working your way down through the chip(s). Here you strive to abrade it in place as it is formed, switching sides as necessary.

Also note that if you simply grind on one side of the blade until you get burr, you are temporarily changing the blade's symmetry and creating a burr off center of where your final edge will reside anyway, which is rather pointless. Here light abrasion removing the burr in place rather than bending it over back and forth is preferred or trying to rip it off running through a cork, felt or the end of a piece of wood. When I resort to this, it is due to either very casual technique on very cheap knives or a personal failure of my technique not meeting my own standards.

---
Ken



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 Post subject: Re: Starting a new edge?
PostPosted: Sun Feb 16, 2014 10:00 am 
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It's really simple when you think about it. When you take the edge across the stone (@15 degrees) in an edge-trailing fashion, there is obviously going to be far more metal being pushed down to the edge and over it, then there will be if you do the same thing in an edge-leading fashion. That's just physics. The amount of slag, depends on pressure. Then, (if edge-leading) we turn the knife over and go the opposite way, the stone automatically debur's any slag off the opposing side that you just sharpened. As we keep sharpening (gently) in an edge leading fashion, each opposing stroke, removes any slag that we just created in the previous stroke. The lighter the stroke, the less we need to worry about it; we end up with essentially zero burr. A quick little run through a cork, to clean it up...and it's perfect.

Light, edge-leading strokes.

Once again, this became entirely obvious to me, from watching razor honers do their magic. They only use edge leading strokes. Where edge quality is more critical than any other discipline, because it's being used on the skin, on your face and neck. With a few edge-leading strokes (on my setup), I'm instantly back in business, and I don't use a strop either, because I find that my Coticule is just about right for the edge I like to use on food.

machine-sharpened-knife-is-sharper-than-my-others-t5267.html


Yawn, back to bed.



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