Rambling thoughts on gyuto profiles

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Nikabrik

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Interesting! It looks like you're using a lot more "weight" on P1, and less on P2 compared to what I've been doing. Yours definitely looks like a better fit than mine. My points were adding extra "tip belly" - drawing P2 closer to the tip reduces that, and P1 has a remarkably strong yet graceful impact way up there, filling out the rest of the belly.

FWIW, Matus has some additional specs on that Kato in this Gyuto design article.
Mucho Bocho's Kato 240 is 242 long x 52 at the heel.
 
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Kippington

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I tried a Misono Dragon. Your spreadsheet deals with real life examples really well!
It's also a good way of discovering little nuances I had never noticed before. For example, the belly of this knife flattens out towards the tip. You can spot it a mile away in the Edge Curvature graph.

I bought some 1mm spacing graph paper that helps accurately find the points.
 
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Kippington

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And the whole shape gets neatly summed up as the following:
Misono Dragon 240mm
P1 - 143.3
P2 - 202.2, 1.9
P3 - 246.5, 21.5
Heel Height - 50.5
Spine Angle - 3.6°​
 
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Kippington

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Tojiro DP 240mm
P1 - 171
P2 - 206.2, 6.9
P3 - 236.5, 18.9
Heel Height - 49.8
Spine Angle - 3.5°​

I wonder how many knives I'll end up doing...
 

Kippington

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A personal favorite of mine:
Sukenari 240mm
P1 - 141
P2 - 197.7, 1.5
P3 - 229.5, 18
Heel Height - 51.2
Spine Angle - 3.1°​

Can anyone that owns one of these knives test my measurements? I'd like to see how accurate this is against other knives from the same production run.
All you gotta do is punch in the numbers I've posted here into the spreadsheet, change the graph on your screen to the right millimeter scale then hold the knife up and take a picture.
 

merlijny2k

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Wow, bezier curves. Never heard of them but pretty cool stuff!. I was thinking of just taking a third or fourth order polynomial and solving the coefficients from the boundary conditions. This system is much more advantageous and easier to automate though. Wonder why they are in none of the mathbooks I know. Still got a couple of more advanced books on a harddrive somewhere. See if those get me anywhere.
 

Hanmak17

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I'll be really impressed when you guy's can map the grind of a knife...o_O
 

Nikabrik

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I'll be really impressed when you guy's can map the grind of a knife...o_O
We've seen a variety of reviews showing thickness at various points, but not typically a good representation of radius, depth of concavity - likely due to not having the right measuring instruments.

I've got some ideas, and I've been trying to analyze S-grinds from photos. There's an issue with pinhole effect, though, which needs to be sorted through.

Wow, bezier curves. Never heard of them but pretty cool stuff!. I was thinking of just taking a third or fourth order polynomial and solving the coefficients from the boundary conditions. This system is much more advantageous and easier to automate though. Wonder why they are in none of the mathbooks I know. Still got a couple of more advanced books on a harddrive somewhere. See if those get me anywhere.
Yeah, I think they're predominantly used in computer graphics, so there's probably some coursework somewhere that covers it. They're just a 3rd order parametric polynomial though, in this case - but yes, there are some real advantages.

I tried a Misono Dragon. Your spreadsheet deals with real life examples really well!
It's also a good way of discovering little nuances I had never noticed before. For example, the belly of this knife flattens out towards the tip. You can spot it a mile away in the Edge Curvature graph.

I bought some 1mm spacing graph paper that helps accurately find the points.
What a great idea with the graph paper! Interesting point about the tips. I'd be very curious to eventually see a comparison of the way the knives cut (subjective profile analysis) vs their curvature.
 
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Nemo

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What was that movie, House of Flying Daggers?
 

Kippington

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House of Flying Gyutos, haha! :p

I can think of a good method to classify cross sectional geometry. Maybe I should start another rambling thread on the grind... :rolleyes:
 

RDalman

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The differences on grind that matters most for the cut (near edge geometry/relative assymetry and straightness) are so minute (from makers view) I actually think more they come down to execution than design these days.
 

Nemo

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House of Flying Gyutos, haha! [emoji14]

I can think of a good method to classify cross sectional geometry. Maybe I should start another rambling thread on the grind... :rolleyes:
LOL.

The new thread could be interesting
 
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RDalman

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But that's kindof my stance on profile too haha. They're connected though because they're a result of the final grind work.
 

Kippington

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I'd be very curious to eventually see a comparison of the way the knives cut (subjective profile analysis) vs their curvature.
A quick thought:
The effect of any edge curvature within reasonable boundaries isn't so important if you lift the knife up off the board between cuts. However if you start using rocking cuts, the edge curvature begins to influence how the knife will move. The part of the edge in contact with the board becomes the fulcrum of a second class lever along the horizontal plane, the food is the load and the effort is supplied through the handle. A fulcrum on a rocking knife which changes its position in an intuitive fashion is easier to use.

Basically what I'm trying to say is: If you use a knife with two flat spots, it would be weird to rock chop. Similarly, walking the board is also affected.
None of this comes into play if you lift the knife off the board.
 
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refcast

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Do you guys like profiles that sweep up abruptly at the tip like toyama or masashi?
Or do you prefer profiles with a more continuous, constant curvature like Hinoura, masamoto KS?

I kinda like more continuous curved profiles.
 

bahamaroot

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A quick thought:
...
Basically what I'm trying to say is: If you use a knife with two flat spots, it would be weird to rock chop. Similarly, walking the board is also affected.
None of this comes into play if you lift the knife off the board.
Bryan Raquin did a pass around about 2 1/2 yrs ago with a knife he made that had a "two tiered" profile or two flat spots very much like this. It wasn't met
with much enthusiasm. The transition from the one flat to the next gave it a weird feel on the board and made rocking and walking the board more uncomfortable
as Kipp pointed out. The added longer flat at the tip didn't seem to be of any real benefit either.
 

HRC_64

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The KS has a nice forward cutting area and its not dead flat..
you don't want "flat spots" to be dead flat all the time...
 

Kippington

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I kinda like more continuous curved profiles.
Me too, although they tend to be a little worse for chopping.
In the past I've tried to get the curve as close to a straight line that I can... but here's the problem, I can't account for the flatness of any given cutting board - and lets be honest - pretty much none of them are dead flat. So if I want to prevent the dreaded "flat-spot thud" on a slightly dished cutting board, I end up with more curve at the flat then I would otherwise prefer. The resulting shape looks like a continuous (but increasing) curve, much like the KS.
The KS has a nice forward cutting area and its not dead flat..
you don't want "flat spots" to be dead flat all the time...
 

DitmasPork

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A personal favorite of mine:
Sukenari 240mm
P1 - 141
P2 - 197.7, 1.5
P3 - 229.5, 18
Heel Height - 51.2
Spine Angle - 3.1°​

Can anyone that owns one of these knives test my measurements? I'd like to see how accurate this is against other knives from the same production run.
All you gotta do is punch in the numbers I've posted here into the spreadsheet, change the graph on your screen to the right millimeter scale then hold the knife up and take a picture.
Curious on why Sukenari is a 'personal favorite' of your's? I've never used one, but have handled a few in stores. What made you favor Sukenari over some of the other classic profiles like Mas KS, Shig, Watanabe, etc.
 

HRC_64

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CTs we do at work give us 1mm and 3mm slices.
AFAIK... I think we are talking nominal vs actual numbers
and probably saying the same thing...see, eg

Automatic registration accuracy is greatest when 1.0 ≤ Δτ (mm) ≤ 3.0 is used. Contrast-to-noise ratio is optimal for the 2.5 ≤ Δτ (mm) ≤ 5.0 range. Therefore 2.5 ≤ Δτ (mm) ≤ 3.0 is recommended for kVCBCT patient registration where the planning CT is 3.0 mm.
 
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Matus

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I'm not sure what you're trying to tell me.
I actually think I follow, but let’s just get this thread back on the track and not continue a discussion on CT scanner parameters :)
 

Migraine

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Well I follow what he's quoted, but it doesn't change what the CTs I see actually are so I don't know what the intention behind the post was. But anyway.
 

Nikabrik

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CT scans notwithstanding, here are a few ideas I've had for digitizing grind:

  1. A pantograph which draws on a smartphone screen using a stylus.
  2. A pin contour gauge, which is photographed or scanned.
  3. Project a laser line, photograph from an angle, and correct for perspective - inspired by this: https://hackaday.com/2013/05/15/3d-scanner-with-remarkable-resolution/
  4. Draw a fine-tip sharpie line using a straightedge, and photograph similar to #3. I'm going to try that this Saturday, hopefully.
If #4 fails to produce useful results, I can get a line laser for about $10. I don't think #4 would work well with kurouchi, unless you applied tape first.
 
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