Full Flat Grind Strength

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SpyderEdgeForever
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Full Flat Grind Strength

Postby SpyderEdgeForever » Thu Jan 30, 2014 11:05 pm

As far as blade grinds go, and energy expenditure goes, would you say the full flat grind is alot stronger than other grinds, except perhaps the saber grind?


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Holland
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Postby Holland » Thu Jan 30, 2014 11:13 pm

Are you referring to the edge? or the blade itself?
i think FFG would snap in half faster than a hollow grind. but i think the edge wouldnt chip as easy on the FFG
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Postby Freman » Thu Jan 30, 2014 11:15 pm

Strongest blade (if someone is sad enough to use a blade like a prybar) is probably a tanto, or something else where the spine of the blade goes almost to the tip.

The full flat grind is not as strong as a tanto but it is a good slicer. Since a knife is supposed to cut stuff the full flat grind gets a thumbs up from me.

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Postby Holland » Thu Jan 30, 2014 11:22 pm

Freman wrote:Strongest blade (if someone is sad enough to use a blade like a prybar) is probably a tanto, or something else where the spine of the blade goes almost to the tip.

The full flat grind is not as strong as a tanto but it is a good slicer. Since a knife is supposed to cut stuff the full flat grind gets a thumbs up from me.
Tanto refers to just the type of tip the knife has, don't think it refers to the grind ;)
Also i bet chisel grind would also be stronger
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Postby chuck_roxas45 » Fri Jan 31, 2014 12:16 am

Freman wrote:Strongest blade (if someone is sad enough to use a blade like a prybar) is probably a tanto, or something else where the spine of the blade goes almost to the tip.

The full flat grind is not as strong as a tanto but it is a good slicer. Since a knife is supposed to cut stuff the full flat grind gets a thumbs up from me.
How do you figure that? Any data you care to share?

How about a 10mm thick FFG knife vs. a 2mm thick tanto? Which would be stronger in a prying contest?

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Postby Freman » Fri Jan 31, 2014 1:59 am

A 10mm thick tanto blade, where much of the blade is 10mm wide up close to the tip would be stronger than a 10mm FFG which has a definite taper to the point.

A 2mm thick tanto blade, where much of the blade is 2mm wide up close to the tip would be stronger than a 2mm FFG which has a definite taper to the point.

And I shouldn't have to say, "all else being equal."

The OP suggested that the FFG is stronger than other blade grinds, and assuming that all other factors are the same (length, width, depth, blade material) is an implicit part of shape comparisons.

Holland is correct that "tanto" is a tip shape, but as an example the Cold Steel Voyager tanto is hollow ground up to about half the depth of the blade, leaving a solid strip of steel at the top of the blade. I would say that any grind that maintains that kind of upper strength, sabre, hollow, scandi off the top of my head, would be stronger than an FFG, "all else being equal." A full convex might maintain the greatest cross sectional area through the blade.

Yes, I had the hollow ground Voyager Tanto in mind when I mentioned the tanto, rather than accurately identifying the grind type.

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Postby Evil D » Fri Jan 31, 2014 3:10 am

This is really going to go nowhere fast. There are far too many variables to consider in order to make a clear comparison. As Chuck pointed out the actual grind itself makes all the difference. Spyderco is big on adding distal tapers to their grinds which is what makes the tip thinner than the tang, so you can't even blame stronger tips on one grind vs another. The Rock Lobster doesn't have any taper but it full flat and the blade is the same thickness all the way until it drops down for the tip. What about thickness behind the edge? There's nothing stopping a full flat from being 2mm thick behind the edge and just have a really wide edge bevel, and then have a 4mm spine. Compared to an equally thick hollow grind with a 4mm spine, I would put my money on the thick flat grind as it has more metal overall and is more evenly distributed than the hollow.
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Postby chuck_roxas45 » Fri Jan 31, 2014 3:41 am

Freman wrote:
A 2mm thick tanto blade, where much of the blade is 2mm wide up close to the tip would be stronger than a 2mm FFG which has a definite taper to the point.
Why does an FFG have to have a taper? Where are you getting that? Just because Spyderco uses a distal taper on most of it's FFG's? Aren't most axes ground full flat? I wouldn't say an axe blade is weak.
Freman wrote:A 10mm thick tanto blade, where much of the blade is 10mm wide up close to the tip would be stronger than a 10mm FFG which has a definite taper to the point.
Assumning that there is a distal taper, how much of a distal taper is there(in degrees)? At which point of the two knives would you measure strength? Just beside the tang? Midpoint?

If you do measure near the tip, then you are not measuring the strength of the whole blade but rather just of the tip. If the FFG's tip breaks off, then at most you could say that the FFG is weaker than the tanto measuring ____ units from the point.
And I shouldn't have to say, "all else being equal."
The problem is, all else are never equal. You should really qualify your post as being your opinion and not present it as fact.

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Postby The Deacon » Fri Jan 31, 2014 5:27 am

I could be wrong, but I'm inclined to think that removing material rarely, if ever, adds strength. I would assume, for example, that a 4" long 1" wide, 1/8" thick bar of a given steel at a given hardness will be stronger than any blade you grind from it. If that's true, and assuming we're talking blade strength rather than just edge strength, then if someone were to start with a dozen bars like that, and grind a dozen blades that were identical except for the grind, then whichever blade's grind removed the least material from the bar would be the strongest. How well it would cut, comparatively, is a totally different matter.
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Postby Blerv » Fri Jan 31, 2014 7:41 am

Typically ffg has more material behind the edge than a hollow grind but less at the spine. Most of Spyderco's ffg's though are ground very aggressively and with the distal taper the tips are quite a bit thinner, so toughness is traded for slicing geometry.

Really, it's all the end grinding process and when the maker throws in the towel (or turns off the belt).

Also, a sharp blade slices better than a thick dull one. Given that even thick folding knives aren't using "tough" steel it's entirely possible to snap one even it has more lateral toughness on paper.
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Postby Jazz » Fri Jan 31, 2014 8:28 am

A high flat grind gets a thumbs up from me. Strong and good slicer. Tired of thin FFG.
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Postby Blerv » Fri Jan 31, 2014 8:41 am

Some FFG from Spyderco are almost regrind geometry. They dance the OEM line very well.
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Postby xceptnl » Fri Jan 31, 2014 9:28 am

I would say tip strength is greater in an FFG than in a HG of the same stock thickness. This is clearly obvious when comparing the Manix 2 models. The tip on the HG is clearly more acute and therefore less substantial. Inversley the strength of the HG would be greater at almost anywhere else along it's length when comparing cross-sectional area.
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Postby Fred Sanford » Fri Jan 31, 2014 10:56 am

Blerv wrote:Typically ffg has more material behind the edge than a hollow grind but less at the spine. Most of Spyderco's ffg's though are ground very aggressively and with the distal taper the tips are quite a bit thinner, so toughness is traded for slicing geometry.

Really, it's all the end grinding process and when the maker throws in the towel (or turns off the belt).

Also, a sharp blade slices better than a thick dull one. Given that even thick folding knives aren't using "tough" steel it's entirely possible to snap one even it has more lateral toughness on paper.
Blerv wrote:Some FFG from Spyderco are almost regrind geometry. They dance the OEM line very well.
Blerv has it right on. Well said.

The only thing I can add is that full flat grind blades have been used for a long time, even back in the traditional days of old. They are plenty strong behind the edge. In fact, all grinds are pretty strong behind the edge because knives are made for cutting. If you are talking about the strength laterally when prying then I would agree with Paul (The Deacon).
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Postby bearfacedkiller » Fri Jan 31, 2014 11:10 am

Isn't a convex grind the strongest. Like and axe.

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Postby xceptnl » Fri Jan 31, 2014 11:23 am

bearfacedkiller wrote:Isn't a convex grind the strongest. Like and axe.
The convex is considered amongst some to be the strongest grind and to have the strongest edge.
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Postby razorsharp » Fri Jan 31, 2014 1:59 pm

I didnt read this, but what about a full flat tanto vs a saber drop point :)

Too many things to consider

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Postby The Deacon » Fri Jan 31, 2014 2:22 pm

Somewhat off topic, but has anyone every offered what I'd describe as a "reverse sheepfoot" blade? That is to say, a straight edged blade with an edge that curves up to meet the spine the way a sheepfoot's spine curves down to meet the edge.
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Postby Freman » Fri Jan 31, 2014 2:30 pm

You mean like a Opinel?

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Postby xceptnl » Fri Jan 31, 2014 3:03 pm

I think I have seen some fixed blades in a modernesque tanto configuration where the change was a sharp curve and not a traditional tanto point.
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