What is this compound grind called?

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St33L

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Dec 18, 2013
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What is this compound grind called?

That is, is there a specific terminology for this grind, where the primary bevel is convex, the secondary bevel is concave, and the edge is convex?

I could call it a compound grind and specify the shapes of each bevel... but it would be simpler to describe it if there is an actual term for it.

Thanks in advance!

Compound%20Grind_zpsofpr2j7d.png
 
Would that be a convexed hollow grind? It definitely is some sort of hollow grind?
 
Three different grinds?!? Never see or heard of such a thing.

Closest would be a hollow scandi with a convex edge and with the shoulders at the unground/ground join rounded off.

Seems pointlessly complicated, IMHO.
 
marcinek said:
Three different grinds?!? Never see or heard of such a thing.

Closest would be a hollow scandi with a convex edge and with the shoulders at the unground/ground join rounded off.

Seems pointlessly complicated, IMHO.
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To make it relatively less complicated, how about if you start off with a full convex grind, then remove material on the secondary bevel area to make it concave?

The bottom of the blade flat to the shoulder can be convex, which transitions into a hollow grind, which in turn transitions into a convex edge.

Essentially, as you and another have mentioned, it's a hollow grind with a convex edge. The primary convex would transition as part of the blade flat.

I think it'll be neat - meat/weight on the edge, less contact friction on the secondary bevel, and the convex transition from the blade flat would be more for aesthetics.

Would this negate the benefits of a hollow grind without any added benefit? Wouldn't the meatier edge contribute to a little more energy transfer to the edge, sort of like the energy transfer of an axe, but not nearly as much?
 
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St33L said:
I think it'll be neat - meat on the edge, less contact friction on the secondary bevel, and the convex transition from the blade flat would be more for aesthetics.
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To each his own, I guess. And the old "convex edge has more steel behind the edge" thing.
 
Or, to put it another way in terms of this grind's application... what if the entire stock is a full convex grind, and a "fuller" is added across the entire length, creating the image in the original post?

So, it's like an I-beam where "unnecessary" metal is removed, which also behaves as a secondary bevel for less contact friction, while having more metal behind the edge compared to a hollow grind.

Again, this would pretty much be a hollow grind with a convex edge, but it'll be a little bit more... "refined".
 
In all honesty I can see no real world advantages other then speculation on a drawing " nothing new under the sun"
Its not promeniet for a reason.
There however might be so artistic value to the grind. Maybe it looks awesome?

In the end, id have to see it on a knife to be the judge as well as use.

Otherwise, endless speculation.
 
DeadboxHero said:
In all honesty I can see no real world advantages other then speculation on a drawing " nothing new under the sun"
Its not promeniet for a reason.
There however might be so artistic value to the grind. Maybe it looks awesome?

In the end, id have to see it on a knife to be the judge as well as use.

Otherwise, endless speculation.
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I believe some straight razors have this shape, where the blade flat up to the spine is convex (not that it really adds anything to the function).

A number of folks use that grind as their daily go-to razor for shaving... I wanted to see how it would perform on heavier use...

Though, the hollow grind with a convex edge should perform the same... so I agree it would be an artistic difference/value more than anything.
 
St33L said:
..., while having more metal behind the edge compared to a hollow grind.
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For edge grinds for the having the same angle, that is untrue.

It will have more metal behind the edge than a hollow edge grind with a more acute edge angle.

But, trying to demonstrate that using simple drawings and mathematics has proven repeatedly to be tilting at windmills. I'll pass this time! :)
 
axes_profiles.jpg

Isn't this pretty much a standard grind for a decent axe? An example being the far right axe head in this picture. Essentially the same grind as you show, just elongated.
 
It's a very common grind on military sabres as well, where high rigidity was desired with minimal weight. An increase in thickness increases rigidity in cubically but you won't want the whole geometry bloated or the blade weight would co up a lot. Hence fullering. It allows for optimization of weight vs. rigidity much like an I beam. Leaving the edge thicker and convexed is for durability in the given application so the region right at the edge can better resist side loading.
 
I would guess if this was a knife blade it would be due to doing the hollow grind with a wheel and then doing a lot of sanding or buffing to smooth out the grind marks and round the corners. IOW maybe a sign of cheap manufacturing? Or someone had to do a lot of buffing to clean off rust?
 
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