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Salty dog
08-05-2011, 12:46 PM
http://www.youtube.com/watch?v=E7XTGYY4yE0

Vertigo
08-05-2011, 12:56 PM
PUPPY!!!!!!!!


Edit - Oh yeah, simple and to the point video, thanks Salty!

Adagimp
08-05-2011, 01:05 PM
Another great video Salty. No frills, no non-sense, and respectfully informative.

chazmtb
08-05-2011, 01:07 PM
Great vid. How is the flex on the convex grind?

WildBoar
08-05-2011, 01:11 PM
Great video, Scott! One of my few issues with the reground pass-around was the sticking (especially when cutting horiz slices in onions)

This really shows the helpfullness of a convex grind + how well Del has been able to tweak his blades.

Delbert Ealy
08-05-2011, 01:24 PM
Awesome, Thanks Salty.
Del

Salty dog
08-05-2011, 01:52 PM
Great vid. How is the flex on the convex grind?

very little near the tip.

David Broadwell
08-05-2011, 02:38 PM
Thanks for the vid, Salty. Haven't figured out why this is called a "convex" grind. It's a flat grind that's only taken part way up the blade instead of all the way up. Spoke with Del yesterday and he described how he ground the blade on the newer one.

Salty dog
08-05-2011, 02:41 PM
I guess I see convex as being like a hill. Up one side and down the other.

WillC
08-05-2011, 02:57 PM
Salty, thanks for the vid. do you find single bevel knives part food in the same sort of way? I've been flat grinding my knives so far and only convex the final bevel. I improved this a little by adding a 7 degree secondary bevel with a micro bevel primary. Do you think it needs to be convex to achieve this or could it have a partial flat grind, with a high secondary, then weeny little primary. Does the blending really change anything? I'm thinking if you have a high secondary it would be easier to maintain a tiny primary bevel as well, because you can rework the secondary at one angle.

Marko Tsourkan
08-05-2011, 04:25 PM
Scott,
how does Del's convex compare to Carter convex in terms of performance? Carter convexes his blades high. I think the last time I measured, it was 1.5" above the edge on 2.125" tall knife.


M

tk59
08-05-2011, 06:04 PM
1. do you find single bevel knives part food in the same sort of way?
2. I've been flat grinding my knives so far and only convex the final bevel. I improved this a little by adding a 7 degree secondary bevel with a micro bevel primary. Do you think it needs to be convex to achieve this or could it have a partial flat grind, with a high secondary, then weeny little primary.
3. Does the blending really change anything? I'm thinking if you have a high secondary it would be easier to maintain a tiny primary bevel as well, because you can rework the secondary at one angle.
1. Yes.
2. No.
3. It looks more "finished" and yes, to be able to "thin" the knife using the secondary bevel as a guide and then going to the primary bevel prevent a decrease in performance due to thickening of the blade behind the edge.

@Marko: Carter's bevels range anywhere from 1.4 cm to 2.5 cm in width. Del's heel area has excellent performance. He has been optimizing the balance of taper, secondary bevel angle/height toward the tip. I'm assuming that is why Salty is in the process of thinning down his bevels.

markk
08-05-2011, 06:21 PM
thanks for the video. well done and informative

monty
08-05-2011, 06:32 PM
I agree - no BS, just business. This has been helpful!!

apicius9
08-05-2011, 06:42 PM
I like the video, but the scientist in me does protest: Any thoughts about what part of the difference can be explained by the different grind and what by the different surface?

Stefan

JohnnyChance
08-05-2011, 06:48 PM
I like the video, but the scientist in me does protest: Any thoughts about what part of the difference can be explained by the different grind and what by the different surface?

Stefan

You mean does any of it have to do with one being straight steel and the other being damascus?

apicius9
08-05-2011, 06:51 PM
Yep, the knives are different in two variables, the grind and the surface. So if the taters stick differently, it can be because of either one or both. I have no idea, just curious.

Stefan

JohnnyChance
08-05-2011, 07:11 PM
The surface certainly can affect how food sticks, even on straight steel or clad knives, how it is finished (what grit finish, polished, scratch pattern, etc) has some effect. How much it affects it, and how much it varies from straight steel to damascus is probably negligible. I would say the grind is responsible for at least 95% of a blades food release performance, and finish 5% at the most. More so if we are talking a fully polished blade, but that makes it worse not better, so it isn't a good thing that it affects performance as equally (or whatever) as the grind does.

wenus2
08-05-2011, 07:12 PM
Yep, the knives are different in two variables, the grind and the surface. So if the taters stick differently, it can be because of either one or both. I have no idea, just curious.

Stefan

Wouldn't the scientist also expect the straight steel knife to stick more than the damascus one, given the uniformity of it's surface?
:scratchhead:
Perhaps this test actually shows how truly effective the grind is, despite being handicapped by a more "stiction" prone surface.


Good vid Scott, as always. Thank you for the insight. :thumbsup2:

tk59
08-05-2011, 07:18 PM
Yep, the knives are different in two variables, the grind and the surface. So if the taters stick differently, it can be because of either one or both. I have no idea, just curious.

Stefan

Del's deeply etched damascus actually releases food more readily than a more finely finished flat ground blade. If the damascus knife had been polished to the same level as the monosteel blade, Salty would have had a much more difficult time, getting those slices off.

Wow. I was slow on this one. +1 to both JC and wenus.

jason
08-05-2011, 07:55 PM
Scott,
how does Del's convex compare to Carter convex in terms of performance? Carter convexes his blades high.
M


The primary edge may be considered convex because of the natural rocking of the body while sharpening freehand, but Murray grinds his secondary bevels on a revolving waterwheel so his knives are hollow, not convex.

tk59
08-05-2011, 08:00 PM
That's interesting. I suspected as much until I put a straight edge to the bevel. It looks more or less flat although it is admittedly hard to tell. The "convex" Salty is referring to is the shoulder at the transition between the secondary bevel and the rest of the knife up to the spine.

jason
08-05-2011, 08:07 PM
That's interesting. I suspected as much until I put a straight edge to the bevel. It looks more or less flat although it is admittedly hard to tell. The "convex" Salty is referring to is the shoulder at the transition between the secondary bevel and the rest of the knife up to the spine.

I see. Any convex from the shinogi up is happening naturally from the forging process, I would say.

JMJones
08-05-2011, 08:09 PM
I am confused. Is the grind a partial flat grind that does not go to the spine or is the grind convex? Or something different?

Thanks

John

tk59
08-05-2011, 08:09 PM
Actually, I think he literally means the hump right on the shinogi.

JohnnyChance
08-05-2011, 08:11 PM
I see. Any convex from the shinogi up is happening naturally from the forging process, I would say.

Yes, forged knives often have "natural" convexing just from being hammered more in the middle of the blade. Sometimes they actually get thicker down towards the edge again from this, and their thinnest point ends up being in the middle of the blade (minus the actual cutting edge of course).

tk59
08-05-2011, 08:12 PM
I am confused. Is the grind a partial flat grind that does not go to the spine or is the grind convex? Or something different?

Thanks

John

Murray uses a large round stone to cut the partial "flat" ground bevel. Because the stone has a curved surface, it is actually a little concave according to Jason. To me and my straight edge, it appears to be roughly flat.

jason
08-05-2011, 08:28 PM
Murray uses a large round stone to cut the partial "flat" ground bevel. Because the stone has a curved surface, it is actually a little concave according to Jason. To me and my straight edge, it appears to be roughly flat.

I've ground all of mine to be full-flat, but if you were to lay the secondary flat on a rough stone and scratch it up a bit you'll see the hollow in the center - it may be minute on some knives.

@Johnny: The way Murray cold forges he'll hammer the outsides and then go up the middle to eliminate this as much as possible, but no one is perfect. ;)

Marko Tsourkan
08-05-2011, 09:39 PM
Jason,
do you have some kind of software running that notifies you every time Carter's name is mentioned? :)
Salty is a big fan of Carter's knives, so no worries here.

M

@ Scott,
so how does it perform compared to Carter?

jason
08-05-2011, 09:44 PM
No. :)
I just read more, and post a lot less.

Marko Tsourkan
08-05-2011, 10:07 PM
:) Just pulling your leg.

M

jmforge
08-05-2011, 10:19 PM
It only becomes a hollow grind if you leave it in one spot on the wheel. Bill Moran ground his knives freehand on wheels both horizontally and vertically and they were NOT hollow ground. They were convex, but more subtle than ones done on a slack belt. From what I can tell, he basically did the blade in sections like a Japanese sword polisher does and then blended.
Murray uses a large round stone to cut the partial "flat" ground bevel. Because the stone has a curved surface, it is actually a little concave according to Jason. To me and my straight edge, it appears to be roughly flat.

jmforge
08-05-2011, 10:21 PM
Actually, my blades tend to bulge in the middle when forged by hand. I have to go back and fix that.
Yes, forged knives often have "natural" convexing just from being hammered more in the middle of the blade. Sometimes they actually get thicker down towards the edge again from this, and their thinnest point ends up being in the middle of the blade (minus the actual cutting edge of course).

tk59
08-05-2011, 10:32 PM
It only becomes a hollow grind if you leave it in one spot on the wheel. Bill Moran ground his knives freehand on wheels both horizontally and vertically and they were NOT hollow ground. They were convex, but more subtle than ones done on a slack belt. From what I can tell, he basically did the blade in sections like a Japanese sword polisher does and then blended.As far as I know, all Japanese knife makers grind with wheels, as well and they are all convex on one side at least.

jmforge
08-05-2011, 10:49 PM
and the single bevel knives that are hollow ground on the other side are done that way intentionally but pulling the blade along the wheel straight and letting the wheel dig into the center, for lack of a better explanation. Yet the same wheeel is used to produce a every subtle convex grind on the other side of the blade.I convex my blades by grinding on a KMG rotary platen and then flattening/thinning it out during hand sanding or on the flat platen if it is too convexed.
As far as I know, all Japanese knife makers grind with wheels, as well and they are all convex on one side at least.

WillC
08-06-2011, 04:39 AM
1. Yes.
2. No.
3. It looks more "finished" and yes, to be able to "thin" the knife using the secondary bevel as a guide and then going to the primary bevel prevent a decrease in performance due to thickening of the blade behind the edge.

@Marko: Carter's bevels range anywhere from 1.4 cm to 2.5 cm in width. Del's heel area has excellent performance. He has been optimizing the balance of taper, secondary bevel angle/height toward the tip. I'm assuming that is why Salty is in the process of thinning down his bevels.

Thanks very much for wading through that! very helpful, in fact this whole thread has been most thought provoking. Oddly its making me want to give some traditional grinds a go. As I've not even tried them yet. I'm finding the idea of control with the beval parting food to one side appealing and would be interested in seeing how the slight hollow on the other affects things.