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Recent Sharpening Woes

post #1 of 21
Thread Starter 

     I have been the proud owner of a 240mm Kikuichi TKC gyuto for almost 2 years now. It has seen heavy use in professional kitchens, but has never been mistreated or used inappropriately. When I first received it, I would touch up on stones weekly and give a good sharpen on a monthly basis (50/50 edge), 600/1000/4000/6000 stones, honing on fine ceramic frequently. Now I don't consider myself god's gift to knife sharpening, but I know what I'm doing. This knife has been an excellent workhorse and given me no reason to complain until recently. I'm starting to notice the edge retention decrease to the point where I'm sharpening every 2-3 days. I'm also having trouble getting it hair-popping sharp. 

     My theory is that the knife is getting worn down to the point where it needs to be thinned. It doesn't really appear that way; the profile hasn't changed noticeably since I have received it, this is just my educated guess. Any other theories would be appreciated. In the case that it does need to be thinned, I am hoping for someone familiar with the process to walk me through it. Is this something that will need to be done with all knives eventually? It seems I saw a video tutorial a year or two ago but I can't seem to find any now...Thanks in advance.

post #2 of 21

What you're describing doesn't sound like an issue of a thick shoulder to me. A thick shoulder should still take and hold a good edge, but wedge and crack and chip the food being cut. And this knife is thin enough you're not likely to have a significant shoulder.

 

I'd like to say it's the result of differential hardening and you've worn it past the harder edge, but this knife isn't differentially hardened, nor would the hamon have been that close to the edge.

 

Can you post a photo of the knife and its edge bevel?

post #3 of 21
Thread Starter 

700

 

700

 

700

 

700

 

 

Hope this helps.

post #4 of 21

Although his reasoning makes sense, I'm afraid I have to disagree with my friend Phatch.

 

It's almost inevitable for edge angles to become increasingly obtuse as they're sharpened.  One common consequence of obtuseness is the tendency to lose an edge more quickly than a more acute edge.  In addition, they have less perceived sharpness and slight wear can be more easily felt. 

 

Your description applies to a knife which needs thinning.  If you don't thoroughly deburr after sharpening, and/or you do use a rod hone (aka "steel") for maintenance between trips to the stone, it's almost certain.  So:  Neither, either or both?

 

BDL

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post #5 of 21
Thread Starter 

I deburr on a wine cork before moving to the 4k stone, and use a fine ceramic Idahone as needed.

post #6 of 21

Considering everything you've said, I believe your next step should be thinning.  You should probably thin anyway after every four or five times you sharpen more than a "touch up." For a typical home cook, that's about once a year. 

 

What seems to be happening is that you're leaving a slight wire on your edges, and that when it steels or breaks off, the resulting edge is too wide.

 

If you're comfortable with 15* go for that; and err on the side of being more slightly more acute.  FWIW, I don't believe hand sharpeners can hold any given angle with great accuracy and that people who say they hand sharpen at (for instance) 12* are selling you a bunch of fertilizer. Even if you can hold a good angle (and I bet you are), use the Magic Marker trick when you profile to make sure you get a straight bevel without any high or low spots.  Allow the bevel to get wider and more acute as it runs up the belly to the point.

 

In terms of regular sharpening, de-burring should be the last thing you do after a 4K.  It might be a good idea to use your rod to chase the edge a few times before deburring with a cork.  If you feel you lose too much polish, return to the 4K and polish with a few, very light, stropping strokes.  

 

ALWAYS, very very light with the steel; and as few strokes as possible (two per side is usually enough) for ordinary maintenance.  You may want to go more strokes (but just as gentle) to really weaken the burr when chasing it. 

 

FWIW, my current thinning stone for Japanese knives is a Beston 500.  It's not cheap, but is long wearing, doesn't dish way too easily and is almost as good as it gets.  It's something of a PITA because it takes a couple of hours of soaking before using.  The next major step in quality is a Gesshin 400, but they're very expensive -- especially for a stone that won't see much use.

 

Keep asking questions,

BDL

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post #7 of 21

@BDL honestly, i see more use with coarse stones than anything else in my lineup... makes my sharpening quicker, but doesnt mean i have to remove more steel.  I can just get he bulk of work done in seconds instead of minutes.

post #8 of 21
Quote:
Originally Posted by JBroida View Post

@BDL honestly, i see more use with coarse stones than anything else in my lineup... makes my sharpening quicker, but doesnt mean i have to remove more steel.  I can just get he bulk of work done in seconds instead of minutes.


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post #9 of 21
Thread Starter 

From what I understand about thinning, I will be grinding a larger, more acute bevel that runs up the side of the knife. And then I would go back and run through my usual sharpening progression. Is this correct? If so, I have a few questions:

Is there any way I should be measuring this angle?

How far up the side of the knife should the bevel run?

What do you (BDL) mean when you say "Allow the bevel to get wider and more acute as it runs up the belly to the point"?

After thinning on a coarse stone, am I correct to assume that I would continue to thin with my usual stone progression?

Does anybody have a video demonstrating how to properly thin a knife? Or even a picture of a successfully thinned knife would be helpful.

Thanks for all the info.

post #10 of 21

 

post #11 of 21

I meant what Jon demonstrated. 

 

Also, for the little it's worth, I disagree with Jon that a very coarse stone is the right stone for just about anything other than profile or repair.  Coarse stones used for ordinary sharpening with even moderate pressure make for too much tooth, and tooth is inherently weak.

 

BDL

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post #12 of 21

yeah... but the tooth comes out as you move through your progression.  Even if you're just using a coarse stone to get you 1/2 way to where you want to be, its still a time saver IMHO, but at the end of the day, everyone has their own preferences.

post #13 of 21

Jon, I guess I misunderstood what you were saying.  I gathered you recommended a coarse stone as a single stone solution and not as the first stone in a progression.  Glad to be wrong, and imagine my surprise.

 

Apparently we're on the same page, I go down to my coarsest stone (Bester 500) more often than mere thinning requires.  I use it for all sorts of purposes, including getting rid of bending burrs on my thin, hard knives.  On the other hand, I try to be conservative because it takes a lot of alloy. 

 

But my general recommendation to people still learning how to sharpen is stay away from fast, coarse stones until they've (a) mastered angle holding with medium and medium/fine grits; (b) and learned to use coarse stones for mild profiling (e.g., thinning), preferably with the Magic Marker Trick.   

 

It seems kokopuff may have something to contribute as well, but its nature is unclear.

 

BDL

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post #14 of 21
Thread Starter 

Thanks for the info guys. One last question: how do I gauge how much metal to take off? I want to avoid grinding to the point where it becomes detrimental.

post #15 of 21

little by little ;)

 

Just do a bit at a time and see how things work.  At some point, you will see problems occur (chipping, lack of edge retention, etc.) or the knife will show a decrease in performance.  Stop then and back the thinning for a bit (that may also be a good time for a microbevel).  You dont have to thin like crazy.  The idea is to maintain the geometry of your knife overtime... not to make every knife as thin as humanly possible.

post #16 of 21
Quote:
Originally Posted by boar_d_laze View Post

It seems kokopuff may have something to contribute as well, but its nature is unclear.

 

BDL

 

You refer to my use of the corner of the stone for metal removal?  Works great for thinning but may leave some scratch marks alongside both faces of the edge, higher up towards the backbone.!  My edge works for me and I not it.

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post #17 of 21

I feel that the ultimate in sharpening is a belt made of silicone carbide; it's way forgiving and feathers the edge quite nicely.  It's what's used for axes and knives at knife shows and provides the ultimate in sharpness that slices thru the shearest of cloths.  To blazes with stones.

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-T

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post #18 of 21

the edge from a belt (even well done) versus the edge from stones does not compare.  Testing side by side can easily show that.  Also, single bevel knives can not be sharpened on belts.

post #19 of 21

In order to take off the minimal amount of metal, use the Magic Marker trick.  If you're both holding the angle you want and taking the ink off the edge... STOP.  Personally, I keep going if there are any high or low spots.  But that's it. 

 

In terms of finding the new angle -- it's very natural to "click-in" to the old angle.  That is let your wrist find the current bevel and relax into it.  You have to consciously sharpen more acute and hold the angle.  If you use the Magic Marker trick your first strokes won't take any ink off the edge, but only higher up the bevel face.  

 

If you get high or low spots, stop using long "swiping" strokes which sharpen the entire length of the blade.  Section your knife as necessary to remove high spots.  By the time you're taking ink off the edge, the bevel should be flat. 

 

Re-ink as necessary (often!) to make sure you can see what you're doing.  Ink is cheap.

 

Like Jon, I suggest a light touch and taking your time with coarse stones.  Screw up, and you can only fix it on the same or a coarser stone so that mean moving a lot of metal around; which is something you don't want to do.  You've already had enough experience that this shouldn't be a problem. 

 

Hope this helps,

BDL

 

PS.  On another topic:

 

Originally Posted by kokopuffs View Post

You refer to my use of the corner of the stone for metal removal?  Works great for thinning but may leave some scratch marks alongside both faces of the edge, higher up towards the backbone.!  My edge works for me and I not it.

No.  I referred to your bouncing smilie of delight when you thought Jon had put me in my place.  At the time, it was your only post in this thread.  You have not yet described how you use the corner of the stone.  That leaves us with the question.  How do you use the corner of the stone?

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post #20 of 21
Quote:
Originally Posted by kokopuffs View Post

I feel that the ultimate in sharpening is a belt made of silicone carbide; it's way forgiving and feathers the edge quite nicely.  It's what's used for axes and knives at knife shows and provides the ultimate in sharpness that slices thru the shearest of cloths.  To blazes with stones.


Gotta agree with Jon that there is something special about a stone edge. I have a sander and run 40-2000 grit belts of various material on most things but the edge isn't as the same as off stones.

 

Far far faster but not as good. Also every moment of contact with the belt equals many strokes on a stone so any mistakes are magnified.

 

Jim

post #21 of 21
Quote:
Originally Posted by boar_d_laze View Post...No.  I referred to your bouncing smilie of delight when you thought Jon had put me in my place.  At the time, it was your only post in this thread.  You have not yet described how you use the corner of the stone.  That leaves us with the question.  How do you use the corner of the stone?

 

the knife is held at a 45 degree angle to the stone's edge with the knifeedge tilted into the corner.  Keeping the same angle and "tilt", the edge is then drawn downward.

 

EDIT EDIT:

 

With the spine of the knife facing you, it's held at about a 60-75 degree angle to the top surface of the stone with the edge tilted into the corner of the stone.  The the edge is drawn downward and toward you against the corner of the stone.


Edited by kokopuffs - 8/6/12 at 4:50am

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