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View Full Version : Is it me, or is it the usuba?



echerub
11-28-2011, 02:51 AM
I'm getting really frustrated with my econo-usuba. Yeah, I know the usual advice about not buying lower-priced usubas, but I got this thing really early on before I knew any better.

About 2 weeks ago, I figured I'd give the thing a proper sharpening - something I hadn't done on it before. Sometime towards the end of my routine, I decided to check on the edge itself and lo and behold it was like the McDonald's Golden Arches. I had an M-shaped edge profile going on with three points of contact and two slightly arched indents. No freakin' wonder I kept getting accordions with this knife when I used it before! I kept thinking it was just because I was using an older board that might not have been totally flat.

I spent a fair bit of time on some coarse stones thinking I could just work it out. No such luck. Even with a fair bit of metal and stone abraded away, it was still Golden Arches City.

That was 2 weeks ago. Tonight, I figured I'd try fixing the darned edge if I could. This time, I touched up the uraoshi a bit (because I'd worn enough metal away before that there was practically just a hair's breadth left) and then stood the knife on its edge. With the edge right on the Beston 500, I just flattened out the edge that way. Then I proceeded to put on a new, sharp edge on the knife.

At first, I kept checking the edge straightness, and it was a-ok all through my time on the Beston. Then I just continued as usual through the rest of my progression. Finally, after the finishing stone, I checked the edge again... and freakin' hell, I got the M-shape again.

Was it me? Was it the knife?

To try to put my mind at ease, I put a mioroshi deba through the whole sharpening routine. It was a second-hand knife and it had a few nicks in the edge that I wanted to take out. I went through from coarse up to finishing and everything was a-ok. Edge profile maintained, and it's nice and sharp.

What gives with the usuba then? Why is that the only knife that I can't sharpen properly? Is it me or is it the econo-usuba?

ecchef
11-28-2011, 06:35 AM
Gotta be the blade. Something wacky there.

dmccurtis
11-28-2011, 08:20 AM
Your blade road isn't even. You probably have two major overgrinds in the bevel that will need flattening out. Such is the hazard of the cheap usuba.

EdipisReks
11-28-2011, 11:53 AM
the blade road not being even is my guess, too.

JBroida
11-28-2011, 12:25 PM
actually under and overgrinds arent the most likely problem... having a not straight blade is... i would say about 75% of the time people think the problem with their usuba is a grind issue, its actually a blade straightness issue

dmccurtis
11-28-2011, 12:58 PM
Would blade straightness produce the three points of contact as described? I suppose I'm assuming the ura is flat in this case, which made me assume a grind issue.

echerub
11-28-2011, 01:29 PM
Hmm... I didn't notice any lateral waviness when looking down the edge from tip to heel. I also didn't see Abu obvious high-low zones in the blade road based on color and tone.

I'll take a deliberate look for lateral unevenness when I get home later.

JBroida
11-28-2011, 01:56 PM
Would blade straightness produce the three points of contact as described? I suppose I'm assuming the ura is flat in this case, which made me assume a grind issue.

it very well could

Eamon Burke
11-28-2011, 02:44 PM
I was gonna say your stones aren't flat, but if the deba does ok, sounds like a poorly made knife.

memorael
11-28-2011, 05:18 PM
Hopefully I am wrong but it could be your sharpening style too, I messed up an usuba and a muki learning how to sharpen the straight edge knives and a change of pressure or lack of even attention to on spot on the knife leaves those damn M shaped grinds. I used to get one about an inch from the tip and another one about an inch down from the middle, after a while I noticed I would spend significantly more attention on those two spots and very little at the heel producing the M shape. This problem was WAY more noticeable on straight edges. After checking my gyutos they to had an M shape that was very slight and didn't really produce a negative effect, but definitely a problem with what used to be my sharpening style.

JBroida
11-28-2011, 05:29 PM
that is also very true... on really wide bevels, you notice pressure changes more. The place where your fingers are above is where the bulk of sharpening takes place, so you may end up with things that look like high and low spots based on not moving your fingers around enough. Light pressure minimizes this, but its still true.

echerub
11-28-2011, 06:04 PM
Yeah, and that's something I'm a little concerned about. If that is the case, then it's a good thing it's showing up for me with the econo-usuba and not a nicer one :D

Well, I'll take a close look at the knife later on...

slowtyper
11-28-2011, 07:15 PM
Yeah, and that's something I'm a little concerned about. If that is the case, then it's a good thing it's showing up for me with the econo-usuba and not a nicer one :D

Well, I'll take a close look at the knife later on...

You should take it with you to Tosho or knifetoronto (or both even better) and let them take a try with it. Easy second and third opinions and cheaper than buying another if it isn't necessary

echerub
11-28-2011, 09:11 PM
I don't know if my eyes are playing tricks on me - it's such a fine edge - but I think there is a bit of lateral waviness going on. Looking from heel to tip, the middle of the knife curves a little to the right compared to the portions immediately before and after it. The heel and tip are out of focus and doing funky things on me. Astigmatism sure doesn't help when I'm trying to eyeball a thin thin edge like this :)

But if I trust my eyes and it's not just my brain doing some wishful thinking, that slight waviness would make sense. It would put the "arched" areas further "down" compared to the middle of the M. Hence, when sharpening on a flat stone those "down" areas will necessarily wear more.

Yeesh. Man, now I'm *really* starting to get a sense of how freakin' difficult it must be to make these things right!

slowtyper
11-28-2011, 09:38 PM
I totally know what you are going through. I have a usuba that when I first started sharpening I was using way too much force and my blade was very wavy. I ground it flat and resharpened and still wavy. eventually I learned to reflatten the blade, and sharpen it very very slowly and with light pressure and it worked. Occasionally after sharpening now I will hold it up to the light and see some slight wave but I just let it slide now.

But I remember those first few times I kept holding the knife edge up to windows, lights, rulers, the wall, any flat edges I could find in the apartment (I couldn't find anything perfectly straight!) and my eyes were dry as chalk.

Mike Davis
11-29-2011, 12:45 AM
I will also add that it might be a heat treat issue. If you have hardness zones, even if it only varies by 1-2 rc points, it could cause issues. You could theoretically bend the edge by applying pressure when sharpening....If the HT is shot, it might flex and stay flexed. Just another thought to drive your current insanity.

echerub
11-29-2011, 07:45 PM
After a brief chat with the Wizard Out West (that'd be Jon ;) ), I've got a bit of a task ahead now: trying to straighten out edge warpage :D

Thank goodness this is a for-fun knife and not one that I'm relying on...

Seth
11-30-2011, 10:53 AM
I have a 240 nenohi kama usuba; a big beautiful knife for sure. I had some waviness and started checking the geometry against the quartz counter. With back side down there is a slight rise at the curved part of the spine - distal. Flipping over, the blade road is dead flat. I figured then that this was technique. On flat stones I did the blade road longitude direction with light pressure only in areas where the edge humped. I use a microbevel on this knife as well and worked that gently as well. I was able to get the edge fairly straight and over a couple more sessions it should improve. For those lusting after good usubas this is an argument for sticking with 180s or 195s as I expect these would be easier to deal with.
Seth

phan1
12-01-2011, 10:45 PM
I've gotten this before, and I have to say I've never successfully straightened an edge with an "n" or "m". Last time I tried, I destroyed my knife, LOL. It was like the knife was cursed! This is something I always check when buying new knives now cause dealing with such a problem is a huge pain. The only thing I would recommend is keep on grinding away properly, and don't get frustrated and screw up your knife chasing your "m" shape.