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mpukas
03-10-2012, 11:29 PM
I've recently noticed that I really f**king up the geometry of my most used knives (Yusuke 270 gyuto and 210 petty) through my sharpening technique, or lack thereof. When I got into sharpening a little over a year ago, I played with several different techniques, and settled on a full sweep from tip to heel along the entire length of the stone. Recently, however, I've done a couple of Jon's on-line seminars and I now using a traditional Japanese technique.

Somehow I'm putting pressure from the tip back about a few inches and the factory curve in the tip in being flattened out and it's starting to look like a bird's beak. I have an idea of how to go about making it look better by grinding off some of the area at the transition between the main belly and the tip.

What's happening can pretty easily been seen in the photos. The top photo is my 270 gyuto in itís current state. The middle photo is my 300 suji on top (which hasnít been sharpened much, hence it still has the original profile), middle is the gyuto, and bottom is my 210 suji which is starting to show signs of the same deformation. The bottom photo is my 270 gyuto when it was brand new.

I'd really love some feedback as to what I may be doing wrong and what to do to correct it. Cheers! mpp


http://i143.photobucket.com/albums/r141/mpukas/IMG_5154.jpg
http://i143.photobucket.com/albums/r141/mpukas/IMG_5150.jpg
http://i143.photobucket.com/albums/r141/mpukas/2011-04-26053.jpg

James
03-10-2012, 11:39 PM
I used to have the same problem until I switched to a technique Jon showed in one of his videos


http://www.youtube.com/watch?v=tmBTO0cA_qw

The hekler
03-11-2012, 12:35 AM
Dave told us something about fixing this in one of his classes, I don't wanna say something wrong so I'll wait until he comes here and can say it himself but apparently it's a fairly common problem.

zitangy
03-11-2012, 01:05 AM
Technique: whatever style method you prefer.. it is steel removal.

a) You need to be aware of your pressure. SInce it became a bird's beak ard the tip, I believe that as the metal around that area is thinner and thus too much metal has been removed. you need to reduce your pressure when teh tip area is on the stones. Alternatively the amount of strokes required required wld be ;less as it is a thinner areaaround that area

b) When you are sharpening part by part, intersperse it with your long strokes.

c) I have seen the middle of the knife overgrind as they just keep sharpeining on that particular part too much and wonder what happened.

Be more aware its not your technique BUT how it i applied..

have fun

zitangy
03-11-2012, 01:07 AM
"Be more aware its not your technique BUT how it i applied.."
how it IS applied..

Dave Martell
03-11-2012, 01:20 AM
This is a super common problem for a new sharpener to have to get past. The issue is bascially that you're grinding away under the pressure of your fingertips (which are behind the tip because you can't push down at the tip - right?) and this is happening because you're trying harder and harder to get the tip sharp but you're applying too much pressure which does just what you don't want - push the tip away from the stone. The answer to fixing this is to do it right.

What an ass, huh? Yeah that's for sure. LOL :D

So what's right? For starters, use less downward pressure on the (over the stone) hand and raise the handle more to reach the tip. That is what you should've done, what you now need to do is to fix the problem and that's pretty much the same thing except you need to grind away overhang (the beak) at the tip by working from the tip to the flat section behind it. Do this from both sides!

Again this is very common and you're not alone here, I was the king of bird's beak when I started.

JBroida
03-11-2012, 01:24 AM
This is a super common problem for a new sharpener to have to get past. The issue is bascially that you're grinding away under the pressure of your fingertips (which are behind the tip because you can't push down at the tip - right?) and this is happening because you're trying harder and harder to get the tip sharp but you're applying too much pressure which does just what you don't want - push the tip away from the stone. The answer to fixing this is to do it right.

What an ass, huh? Yeah that's for sure. LOL :D

So what's right? For starters, use less downward pressure on the (over the stone) hand and raise the handle more to reach the tip. That is what you should've done, what you now need to do is to fix the problem and that's pretty much the same thing except you need to grind away overhang (the beak) at the tip by working from the tip to the flat section behind it. Do this from both sides!

Again this is very common and you're not alone here, I was the king of bird's beak when I started.

yeah... light pressure and make sure you're lifting up and rotating enough to reach the tip (but not too far)... use sharpie if necessary (no shame in that at all). Its a combination of heavy pressure and not adjusting properly for the tip that causes this. What does your bevel look like near the tip? I cant see in the pictures, but i'd be willing to wager it gets larger right before the tip and then smaller as it nears the tip of the tip.

slowtyper
03-11-2012, 01:29 AM
What SHOULD the bevel at the tip look like? Mine seems to get get larger and larger from the start of the curve to the tip, whereas its pretty even before that. Is that normal or should it be even with the rest of the blade?

Actually I notice that there is an area where the bevel is smaller than anywhere else on the blade right at the section where the tip begins to curve away from the rest of the blade. I sharpen in sections.

Dave Martell
03-11-2012, 01:32 AM
What SHOULD the bevel at the tip look like? Mine seems to get get larger and larger from the start of the curve to the tip, whereas its pretty even before that. Is that normal or should it be even with the rest of the blade?


It's normal to see a wider/taller? bevel at the heel (if the heel is thicker) and a progressively narrower bevel towards the tip as the blade thins. Unless you're using a jig (like an EdgePro) the bevel should be the narrowest at the tip because the blade is thinnest there.





Actually I notice that there is an area where the bevel is smaller than anywhere else on the blade right at the section where the tip begins to curve away from the rest of the blade. I sharpen in sections.

Sounds to me like you're skipping over a section.

bieniek
03-11-2012, 02:11 AM
Also on the chefs knife, around 5cm from the tip it doesnt look too smooth.

Just obcerve carefully where you grind off. If you see its not happening where you want it to be, adjust after every stroke until you find good hand position[and you grind exactly where you should]. Dont stop until you get there. It may take a while, so be patient :)
Then remember it and i think the system is similar for every knife, just angles are different

Eamon Burke
03-11-2012, 02:41 AM
As you learn to do this, prepare to see the most amazing scuffs you've seen yet! I felt all proud about my lack of scuffing until I learned to properly adjust for a tip and blend it into the bevels before it.

I give a big :plus1: to the sharpie trick. I use the same principle on every knife I sharpen, every time, but I just look at the scratches.

memorael
03-11-2012, 03:09 AM
I used to have this problem too! happens to be to much pressure as stated by other pro sharpeners. What happens is the knife flexes, putting most of the pressure on just one spot that starts to grow until it kinda flattens out over a certain area resulting in the birds beak. Basically the tip isn't getting sharpened at all too. Try either Jon's rocking tip or just lift the handle a lot to make sure you hit the tip. The sharpie trick is the easiest trick to do this too btw but IMO has some limitations.

Ontravelling
03-11-2012, 06:53 AM
The sharpie trick is the easiest trick to do this too btw but IMO has some limitations.

What would the limitations be? I thought you applied sharpie to see where you were removing metal? If it wears off I reapply to make sure I'm still hitting the right spots.

Cadillac J
03-11-2012, 10:20 AM
I've never had this problem with tips, but I can understand why it happens. What I've always found to work well is to really try to visualize what part of the edge is hitting the stone as you go along especially when near the tip...once you get it down through visual/feel/sound, you will know how to lift and adjust the handle just right in order to keep the bevel on the stone at the tip properly. As said above, too much pressure and too much time spent in that area are the culprits, its just learning to change those things.

tk59
03-11-2012, 10:37 AM
As others have mentioned, go slow, use less pressure and use marker to show yourself where you are grinding and adjust until you can see you are grinding the length of the blade. (This is for prevention.) For fixing, I'd suggest taking your edge to a stone or a sidewalk and grinding a new profile into it and then resharpening from there. The last thing is I'm all for figuring out what you like best and sticking to it BUT it is pretty clear to me that the larger the motion used when sharpening, the more difficult it is to stay consistent across the entire blade. I would recommend shortening your strokes and sharpening your blade in two or more sections. As you get more consistent, make your sections larger until they span the entire length of the blade.

Seth
03-11-2012, 10:43 AM
One other observation might be that your left hand (if you are a righty) should move across a greater distance than your right hand. If you maintain say a 45* of knife to stone as you move back and forth your grinding will be flat and start to look like a bird's beak. If your left hand moves the distance while your right moves just a little it will help you create the sweeping motion that will follow around the curve of the tip. Also, Salty has a video (I think it's fowler and chosera's or something) which demonstrates a light touch with two fingers right on the tip of the knife - shows the gentle touch required to work on the tip of the knife.

memorael
03-12-2012, 12:35 AM
What would the limitations be? I thought you applied sharpie to see where you were removing metal? If it wears off I reapply to make sure I'm still hitting the right spots.

Well unless you paint the whole knife tip black you could be sharpening at a huge angle and not notice. I guess it doesn't really have limitations, but rather you have limitations because of how much knowledge of knife geometry and its interactions on sharpening stones you have. The sharpie trick is just a tool to learn about this is what I meant.

EdipisReks
03-12-2012, 12:57 AM
fix the geometry on a XXC DMT, then sharpen from there. no point spending tons of time slowly regrinding. the suggestions given so far will do the job, once the profile is reworked. make sure you don't make the tip too thick behind the edge. once you get it you'll have it.

Ontravelling
03-12-2012, 01:06 AM
Well unless you paint the whole knife tip black you could be sharpening at a huge angle and not notice. I guess it doesn't really have limitations, but rather you have limitations because of how much knowledge of knife geometry and its interactions on sharpening stones you have. The sharpie trick is just a tool to learn about this is what I meant.


True that. I see what you mean now.

After a seminar with Jon I now do paint the whole tip. I bought one of those Sharpie Magnums so that in one swipe I can get a good inch of the knife black. I go crazy with the sharpie, it helps a lot. Especially helping me to gain that knowledge of knife geometry and how it interacts with the stones.

quantumcloud509
03-12-2012, 04:05 AM
Man, at least youre learning. Im too frickin scared to sharpen my own knives. Ill only go for it if someone trains me, and i dont know anyone personally who sharpens. :(

Dusty
03-12-2012, 09:12 AM
Your knives are only as good as the edges you put on them. Watch a few videos and get a beater to practice on. There are a lot of super helpful people on this forum as well - as this thread shows

mpukas
03-12-2012, 09:07 PM
Thanks for all the great responses, guys. FWIW, I don't consider myself a novice sharpener and I am by no means an expert. I've had J-knives and have been sharpening them for a little over a year now. I've devoured everything f/ Jon that he has posted, as well as Murray Carter's vids, Salty's, and anything else that I can find that has value. I put into practice what I learn as best I can, and observe what's happening. There's so many other stones and techniques that I really want to try and see for myself the results.

This is just part of the learning process for me. If this hadn't happened I wouldn't have know it was possible or how to adjust for it and fix it (both the knife and my technique). I got the Yusuke knives because (I still feel) they are a great value, and I've got a lot to learn in all aspects of J-knife skills and sharpening technique, so I'm not bothered by having a mis-step like this. Better on this than a custom DT!

Dave - and Jon - have nailed my problem. I have been trying to emulate Jon's technique for sharpening the tip, but I haven't been doing it properly. Instead of putting pressure at the tip I've been putting heavy pressure behind the tip. Hence, that area has been ground away faster. My bevels are getting better in that they are more even and consistent, but as they get to the tip they get narrower. The bevel behind the tip is slightly larger than the rest of the knife. It's been a couple weeks since I sharpened my knives so the bevels aren't very clear in the pics due to patina. I'll post some new pics when I get to fixing the problem - I'm so anxious to get after it, but I've got a lot going on and I'm sure when I'll be able to put some time into the stones. Cheers for now! mpp

Salty dog
03-12-2012, 09:48 PM
Glad you found your solution.

In adition to everything that's been said, consider the angle that part of the blade is hitting the stone. A lot of sharpeners who start at the tip tend to have a steep angle which contributes to the bow.

Sarge
03-13-2012, 02:23 PM
Glad you found your solution.

In adition to everything that's been said, consider the angle that part of the blade is hitting the stone. A lot of sharpeners who start at the tip tend to have a steep angle which contributes to the bow.

Excellent point when you raise the handle to accomodate the tip your angle can be affected this way. My angle actually gets lower near the tip, but the pressure part was a big lightbulb moment for me. I do like the area near the tip a touch flatter than it tends to come standard, so after seeing the problem early and adjusting for it and learning by fixing, I can have that flatter tip section but still avoid overgrindng that section as well.

zitangy
03-17-2012, 11:47 AM
Pressure of the left hand ( assuming you are a right hander)

a) IF the blade is wide enough, try holding the knife this way.. a) left thumb on spine adn 2-3 fingers on the blade.. I believe that you will have better control on the pressure and knife movt.

Whatever works for you and it is your style.. as long as you know where you are grinding and how much you want to grind

have fun