Sabre grind

[Larus]

I just converted a couple of knives to sabre grind. Both knives were used for chopping, thus the strength of this profile was desirable.

Shortly after first use of the meat cleaver, I got the perception that overall performance was better. This was not supposed to be. Everyone knows that a hollow grind is better for slicing. So, I asked my wife to cut up some potatoes. I handed her the meat cleaver. It was sharp, shiny, and clean, so it met her requirements. After a few minutes, she was slicing potatos paper thin. I reminded her we were not making potato chips. She laughed and admitted she was playing with the knife. After some dialog, we concluded that this knife was performing better that our very sharp set of hollow ground kitchen knives.

I understand the concept of dulling a hollow ground knife. The interface of the 2 sides of the knife is smaller than other grinds. Therefore, for a percentage of dulling, the edge is still smaller that a sabre grind for example. But, what about that widely expanding shoulder at the top of the grind? That has to be pushed through whatever you are slicing. Would a gradual linear slope such as a sabre grind not push through the material easier?

I know this contradicts what we have all been told. But, I have this experience, and, I know that a hollow grind is the cheapest/fastest way to put an edge on a knife (round wheel grinders).

Have any of you experimented with sabre grinds for slicing or general purpose?

 

[Esav Benyamin]

I use a flat grind puukko for kitchen work generally. It's from Finland and comes with no secondary bevel. When you converted to saber grind, did you put a secondary bevel on it? If not, you automatically got a sharper edge than if you had. What is the included angle, 10 degrees? If so, this would make up for the broad shoulders. Another thing, how deep is the saber grind? What looks like a short saber grind on a cleaver may be the same angle as the flat grind on my puukko.

Remember, even on an extreme hollow grind like a Sebenza, there is a difference among the actual cutting edges, from the original convex secondary bevel, or a thirty or a forty degree edge you might put on it yourself.

 

[Larus]

Esav,
I did not measure it. I used the same area the hollow grind used. I just worked it on a green stone by hand using the original grind edges as a guide. Knife thickness is probably 3/32 or 1/8. The length of the primary is about 7/16 or 1/2 inch. I put a very small secondary on for edge retention.

I am amazed with the results. I expected it to hold up better for chopping but thought it would feel a little dull when slicing. The slicing performance was surprising.

 

[Crayola]

Your post is confusing for me, because I think you are using the terminology wrong still.

A Saber grind just means that the grind, whatever it is, goes halfway up the blade and the top half of the blade is left at full thickness. SO, you can have a saber-flat, saber-hollow, or saber-convex.

Hollow ground blades are great slicers for shallow stuff, but material can bind on the blades if you cut thick stuff. The reason is that the material goes into the hollow and kinda bangs on top of the inside curve of the hollow.

A saber-flat grind, which I am assuming you are using, can be sharp too if your blade is thin and your sharpening job is good. And, I find that the full thickness top, and especually where this meets the grind and there is that grind line, mades for an interesting functional part of the blade. It will pop off stuff that you are cutting. Slicing tomatoes with a full flat grind blade will make the slices stick on the blade. But with a saber ground blade, I find that the slices will pop off somewhat more.

Good luck.

 

[Larus]

Crayola,
It is a Sabre-flat. Well, maybe not. It is not ground half way up. The knife is about 3 inches wide. It had a hollow grind. Since we use it for chopping, I converted the hollow to flat. The grind is about 1/2 inch.

I thought any double grind flat was sabre. You are saying that sabre means the grind extends half way through the width of the knife?

What would you correctly call the grind I have now? Whatever it is, I like it so much that I will have to do this with other knives. I fully agree with what you are saying about the top of the hollow grind. I cannot think of another reason that this flat grind is so much easier to slice with that the hollow grinds. I am still convinced that the only advantage of a hollow grind is the reduced cost and speed of manufacture. The shape of hollow grind edges does not make any sense to me. It is too weak for chopping and hits sudden resistance when slicing.

 

[Crayola]

Yep! You have a saber-flat. I meant to say that the saber ground blade goes no more than half way up. I think that is the technical answer anyways.

In your conversion, you may have thinned out the edge a bit too, which would improve your cutting performance. I'm glad you found somethign that works so well for you!

 

[Larus]

Crayola,
Thanks for that clarification. I think the edge is thicker. All the way from the cutting edge to the top of the grind, the grind area of the blade is thicker now. This was the objection to flat grinds that the manufacturers claimed was the reason for the hollow grinds. The blade is thinner above the cutting edge, and therefore, sharper after some dulling cuts are made.

As I see it, the hollow grind is perfect for whittling matches. But, any material to be sliced thicker than the grind has to benefit from the flat grind.

Thanks to all for the education. I will report more on this progress in a few weeks after I have some more experience with the sabre grinds.

 

[Cliff Stamp]

If you put a flat grind right over a previously existing hollow grind then you are going to make a thinner profile as you are removing metal. This will produce a higher performing cutting blade assuming that you leave the edge similar or thinner. The same of course would be true of the reverse. If you used hollowed out the flat grind that you have now, the cutting ability would go up again. The would have the net effect of using a deeper hollow grind in general.

Note that while in general you can make statements like a sabre hollow grind will outperform a sabre flat grind for shallow cutting, that is only true if everything else is equal. If you put a thinner edge on the flat ground blade, or the hollow ground blade is of thicker stock, then it doesn't hold. Thus when you are comparing the performance of different grinds, you have to be very careful that the change in performance you are seeing isn't actually being caused by some other difference in the blade(s).


[hollow vs flat]

But, what about that widely expanding shoulder at the top of the [hollow] grind? That has to be pushed through whatever you are slicing. Would a gradual linear slope such as a sabre grind not push through the material easier?

This is true for one type of hollow grind which has the bottom of the grind running parallel to each other on both sides of the blade. They suffer performance on deep cuts just like you describe. However you don't need to hollow grind in that manner. Hollow grinds can act as relief on the faces of blade to prevent wedging on deep cuts. This is how the faces of axes are ground. The hollow grinds are basically scoops out of the primary convex profile. In these cases the start and end of the hollow grind are of similar curvature, where as with the case of grinds you are describing they are perpendicular.

Here is an image of four common grinds. From left to right they are, flat, traditional hollow, convex, and hollow relief on flat. You can also get hollow relief on convex. I have a large bowie that is ground in this manner.

http://www.physics.mun.ca/~sstamp/images/grinds.xfig.gif

-Cliff