Media Mario's Knife

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tk59 said:
No, he meant concave. He's saying Shigs aren't convex all the way to the top of the knife. The top half is slightly concave.
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I don't think anybody (including Mario) is replicating Shigefusa grind. You need to make 7' radius platen to grind the concave, and it really doesn't make much sense if you are starting with a thinner stock (under 4/16"). The concave grind was meant to reduce weight of a knife as much as to improve cutting performance.

Convex grind performs very well and is very suitable for knives made from thinner stock - 4.5mm and down, so why bother and make more work for oneself? The downside of concave grind is that you get wedging if you cut stuff that is taller than your blade, like cabbage.

M
 
tk59 said:
No, he meant concave. He's saying Shigs aren't convex all the way to the top of the knife. The top half is slightly concave.
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That's a silly question.I have owned five different Shigi's and they all did not have a slight concave.
 
RRLOVER said:
That's a silly question.I have owned five different Shigi's and they all did not have a slight concave.
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I didn't think so either but I've checked two of them in the last month and both have a slightly concave section by the spine, according to my straight edge. Next time you see one, do me a favor and take a straight edge to the face and let me know what you see.
 
Actually, all Shigefusa gyuto I looked at (with a straightedge) were hollow-ground. It's invisible to a naked eye, but put a straightedge to the side and you will see the hollow. It runs from the spine to about 3/8 from the edge. For those of you who wondered how Shigefusa can have a beefy spine and thin midsection, this is your answer.

I approximated a radius of the hollow to be about 80". It's done with a sen (a metal scraper), not a wheel. One can do it with a custom radius platen on 2x72 grinder.

M
 
The vintage Dexter-Russel I'm refurbing has that grind. (and many others) I see two reasons. Lighter weight and it brings the center of gravity down.
 
004-43.jpg


This is the Shigi that I loved and there is not a concave grind near the spine.
 
Salty, you still have that Shig gyuto? This would be a spot where your clay test would be very useful!
 
RRLOVER said:
That's a silly question.I have owned five different Shigi's and they all did not have a slight concave.
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Still have any? Maybe the westerns are different, but put a flat edge on the blade face and hold it up to a light. There is a hollow on the upper half of the blade. Slight, but it's there.
 
JohnnyChance said:
Still have any? Maybe the westerns are different, but put a flat edge on the blade face and hold it up to a light. There is a hollow on the upper half of the blade. Slight, but it's there.
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I know the wa's have it, it was silly to think I have the ability to do it.I should have phrased my answer better.I was attempting to get the geometry style of my three favorites.....mizuno,watanabe,and shigi.
 
I'll get some clay soon enough.

Mine is concave at the top half--I didn't know until I started taking a fingerstone to it, and it's a fairly large one--it covered enough area of the blade that I wasn't hitting part of the face.

It's because Iizuka san does not use a belt-sander, so it's going to have a slight natural concavity on large flat portions.

And yes, it does stick when it is in very large things.
 
homer_drool_702026_146.gif


Mario: Congrats!
Im very impressed. I knew you had the interest of making knives, I just didn't know you where that good. You really took me by surprise.
It was completely a breath of fresh air :) Thanks! :)
 
johndoughy said:
...It's because Iizuka san does not use a belt-sander, so it's going to have a slight natural concavity on large flat portions...
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According to Marko (and I think he'd know), they use a scraping tool to shape the faces of the blade.
 
Can someone elaborate on the use of a "scraping tool" vs. a belt grinder please? What is a scraping tool in this situation?
 
It is like a file with no teeth. The edge at the end of the bar is sharpened at a 90º angle and pushed against the item to be scraped. Thin shavings can be produced this was. It is a common method of flattening cast iron surfaces. You put some engineers blue on a true surface, rub the item on it to reveal high spots, then scrape them off with the scraper. This would not work well on a piece of hardened steel, I don't think!
 
SpikeC said:
It is like a file with no teeth. The edge at the end of the bar is sharpened at a 90º angle and pushed against the item to be scraped. Thin shavings can be produced this was. It is a common method of flattening cast iron surfaces. You put some engineers blue on a true surface, rub the item on it to reveal high spots, then scrape them off with the scraper. This would not work well on a piece of hardened steel, I don't think!
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Yeah, it's called a "Sen" and it's a woodworking tool, but at the Shigefusa workshop, they said they use it to flatten the Ura...This sounds mighty strange to me. Maybe they do it before HT? I dunno. I was under the impression this was not done on gyutos, but perhaps it is.
 
I think we are getting off topic here. We don't need to dwell on how Shigefusa make their knives.
This post is about Mario's knife, not Shigefusa. :)

M
 
Good lookin' knife Mario. Sorry to hijack your thread. My apologies.
 
Is it just the picture/me, or are the facets on this thing's wa-handle slightly concave?
 
johndoughy said:
Is it just the picture/me, or are the facets on this thing's wa-handle slightly concave?
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001-60.jpg


It has to be the pic.I use an engineer plate and hand sand.I would have to say this does have some flaws.
 
Well don't tell us what they are, for heaven's sake! It's a fine performing knife, and you aren't taking half a year's salary from someone for it. Just keep it mum.
 
Beautiful knife Mario - very impressive indeed! Really impressed w/ the grind.

Salty - can you share you sharpening/stropping sequence on how you got that thing that sharp? Correct me I'm wrong, but that looks like the sharpest knife-weight tomato test you've posted so far.

Also, what's the edge retention of the steel like? How long does that sharp edge last, and do you find it takes longer or not to get dull? Cheers! mpp
 
Mario sharpened it up to 4000. I did a 6 surface strop on it.

Haven't used it enough to make a call on edge retention.
 
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