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Full Height Flat Grinds have weaker V-edge stability

Posted by Gaston444 
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Full Height Flat Grinds have weaker V-edge stability
August 02, 2020 12:14AM
This is a “discovery” I just made concerning thin/bending or otherwise non-stabilized small diameter branches, when subjected to extensive chopping with fairly thin edges of moderately low angles: Say a 0.020” to 0.025” edge base with a V-edge of 15 dps, and a micro bevel of around 20 dps.

I will specify that Full Height Flat Grind I define as a single flat surface to the spine with a separate V-edge angle about 1-2 mm from the apex: I will refer to this as “FFG”, as the notion of a full height Scandi edge I consider of no interest here. I will not discuss steels either, as the effect of twisting is similar across a wide range of steels.

For simplicity I will refer only to V-edges, as I did not test similar thickness convex grinds.

The issue I “discovered” is the action of twisting thin branches, which to my surprise always caused heavy twisting apex damage to knives that otherwise held their edges very well on thicker, more “stable” wood targets. The common thread between all these failing “good” knives only later became apparent to me: All were FFG profiles as I defined above. By contrast, Sabre Hollow Grinds appeared comparatively exempt from this severe apex stability issue, this also across many different knives and steels: Al Mar “Special Warfare”, Randal Model 12 Sportsman/14 grind, Colin Cox 10.5” Survivor, and others.

Here is what I think is the major issue for thin-edged knives used to clear hard, dried-out, but still flexible branches: Sabre Hollow Grinds approach the edge base with nearly or perfectly parallel opposite sides: This means any V-edge angle will cause a transition angle equal to the dps angle. This is NOT the case on a FFG as defined above: Thus inevitably, the edge shoulder is less “prominent”, EVEN with an absolutely identical V-edge...

The mechanism is this: As the branch twists on a Sabre Hollow Grind, the more prominent V-edge shoulder acts as a pivot point on the side opposite the direction of twist, thus protecting (at least partially) the apex from taking on this sideway pivot role. On a Full Flat Grind, the lesser prominence of the V-edge shoulders means that, for a given amount of twist, the opposite twist direction edge shoulder will “unstick” earlier, as it’s lesser “jutting” prominence means the edge apex will “take over” the role of pivot earlier in the lateral rotation. This means an earlier pivot role for the very weak apex.

This is aggravated by the thicker FFG cross-section near the edge base, as it means the wood is being compressed harder by a given twist. This increases the strain on the weaker more apex-oriented pivot point, while the thinner sides of the Sabre Hollow Grind puts less stress on its stronger more edge shoulder-oriented pivot point. It is two effects compounding one another.

The effect of this on 0.020” thick edges is so noticeable it should absolutely exclude Full Heigh Flat Grinds on broad use large choppers/Survival Knives: Clearing a path of flexible thin branches, as a machete substitute, is a perfectly reasonable task to expect of such knives, even with such thin edges. This “new” effect is separate from the greater edge protection of Sabre Hollow Grinds noted in thicker, more stable wood: The edge protection in that case was that the faster thickening of the Hollow Grind “spreads” the wood apart, away from the edge below, or prevents lateral twisting if no spreading occurs. So the Sabre Hollow Grind has multiple interacting layers of edge protection when chopping into wood, even with thin, meat-slicing capable edges. Yes the Sabre Grind shoulders might bind in deep wood cuts, but overall the profile seems far more versatile than currently assumed...

I will try posting images explaining this.

Gaston
Re: Full Height Flat Grinds have weaker V-edge stability
August 02, 2020 02:12AM
Just to clarify, is the claim :

-a flat grind with a given edge thickness is more prone to damage in the primary grind than
-a partial high grind with the same edge thickness, but which is thinner above the edge
Re: Full Height Flat Grinds have weaker V-edge stability
August 02, 2020 07:44PM
If “thinner above the edge” for same thickness edges implies by necessity that it is a hollow grind, then yes that is what I meant.
The more prominent edge shoulders act as a greater protection to lateral twisting (of the knife or of the target material), despite identical V-edge dimensions.

I’ll throw in other beneficial effects of Sabre Hollow Grinds for chopping applications, when compared to FFGs:

-(Already mentioned) Greater wood-spreading effect in thicker wood, protecting the edge through faster blade cross-section thickening (but this evident only on fairly low-set Sabre Hollow Grinds: By contrast, on a fairly high set Sabre Hollow Grind like on Randall’s Model 12-9 (well over 1 inch in height) Randall resorted to the interesting compromise of “stopping” this deep hollow grind to a thicker edge base (0.030-0.035”?) about 1/8” or less above the edge, the concave then transitioning to a very short convex area tapering to Randall’s typical 0.020” V-edge base. This appears to be very consistently done across all recent 12-9s, a quite skillful display which is surprising given the “looseness” of Randall on other models...

Just as interesting is that on their much heavier and larger Model 12-11 “Smithsonian”, 3/8” spine vs 0.22” on my 12-9(!), this short convex “precaution “ is clearly absent, despite V-edges that are similar in thickness. Two reasons would explain this in my view: The Sabre Grind is much lower on the Smithsonian, even in absolute terms, being around an inch, and second, the 32 ounce weight means the knife will always bite deep enough for the Hollow Grind to spread the wood and protect the edge. On thin branches the more prominent edge shoulders seem to have been enough to divert twisting from the apex. It does seem to show Randall cross-sections are refined based on user feedback over the decades...

Other Sabre Hollow Grind advantages:

-Edge thickness remains the same as sharpening wears upwards on the blade. (A major consideration I would think)

-Softer impact on the hand when chopping (from less initial deceleration).

-Less “sticking” compared to FFGs due to concentration of pinching pressure on a narrower height (similar to convex but with an opposite shape).

The only major disadvantage I see to Sabre Hollow Grinds is when narrowly focusing on straight-through cuts on larger diameter limbs. This appears to be the primary concern of many chopping designs like Busse, as shown by their interesting use of corrugations on some blade sides: Almost no chopper design out there mimics the Randall Smithsonian in having a relatively low-set Sabre Hollow Grind, yet this design does allow for a thinner more versatile edge at only a moderate cost in deep straight through cuts (through what seems to me as unrealistically large limbs)... I would be curious to see the Smithsonian compared to similar size Busse and see which knife proves more versatile. The Smithsonian is not much pricier (or heavier) yet is largely treated as a wall hanger these days.

Gaston
Re: Full Height Flat Grinds have weaker V-edge stability
August 02, 2020 07:55PM
I’ll just add something about “damage into the primary grind”: Yes that may seem odd, but if the strain is more biased towards the apex, then the height of the V-edge provides now a small “lever”, however short, that indeed allows more damage to spread “into” the primary grind, even if that primary grind thickens faster...: This is exactly what the damage looks like: The strain on the apex gains a “lever” from the edge height and this pulls on the primary grind. On a hollow grind the strain is immediately on the edge base, so without the leverage needed to distort even that weaker edge base. Also, much of the damage I worry about is confined to the V-edge, with no migration into the primary grind, and yet that is still major edge damage... G.
Re: Full Height Flat Grinds have weaker V-edge stability
August 03, 2020 01:42PM
Ok, second question what is the damage :

-in the apex
-in the edge
-in the primary grind
cKc
Re: Full Height Flat Grinds have weaker V-edge stability
August 04, 2020 03:01AM
Quote
Gaston444
Here is what I think is the major issue for thin-edged knives used to clear hard, dried-out, but still flexible branches: Sabre Hollow Grinds approach the edge base with nearly or perfectly parallel opposite sides: This means any V-edge angle will cause a transition angle equal to the dps angle. This is NOT the case on a FFG as defined above: Thus inevitably, the edge shoulder is less “prominent”, EVEN with an absolutely identical V-edge...

please draw a picture with specific detail, I can't follow you.

or edit and repost this.. add some actual angles, cross section thicknesses etc etc


----------------------------------------------------------------------
It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Full Height Flat Grinds have weaker V-edge stability
August 04, 2020 06:54PM
I cannot post images from my phone, but your drawing illustrates well the more prominent edge shoulders, although it might be a slight exaggeration to some actual blade shapes.

I will try to post photos of the damage later. The important issue is where the lateral load gets distributed: Say the FFG gets 50% directly on the edge shoulder, and 50% near the apex, then the more prominent hollow grind edge shoulder might be 60% on the shoulder and 40% on the apex, just by calculated prominence difference (if this could be calculated). The actual load difference could, however, be much larger than even the theoretical “prominence” load figure: This is because the wood pinching action (from being cut) contributes to the stability of the edge shoulders inside the wood. A more prominent hollow grind edge shoulder would concentrate the available pinching action on the shoulders themselves: This would have a major effect on the amount of “rotation slippage” that a thin twisting branch would have on the outside rotation side of the edge. Wood “rotation” around the edge shoulders (mostly from the outside rotation side slipping down) would be impeded by the more prominent edge shoulder “ridges”, and this would reduce the proportion of lateral load on the apex beyond what the shoulder prominence alone would indicate.

There is a third effect that further stabilizes the hollow grind edge compared to a FFG: Being thinner behind the edge shoulders means less thin branch “pushing”, and this means deeper penetration into a moving branch: Deeper penetration means more intense wood pinching, so even less “rotation slippage” and even better edge stability inside the branch. This alone could be the bigger effect in reducing the lateral load on the apex.

Lateral loads at or near the apex (heavily related to in-wood edge stability) are the critical factor because the height of the apex above the edge shoulders is a 2:1 leverage ratio on a 15 dps/30 degree inclusive edge. Say it takes 60 pounds per mm to deform laterally a 0.020” edge by direct force, then only 30 pounds near the apex might be enough, and any lateral slippage would migrate much of the lateral load towards the apex. Will try to post photos of drawings soon.

Gaston
Re: Full Height Flat Grinds have weaker V-edge stability
August 04, 2020 07:05PM
It still isn't clear to me what is the damage being reduced :

-edge
-apex
-primary grind

Is it all of this?

To clarify what exactly is the evidence for this, I assume it is comparisons on a bunch of blades, can you list them and the specifications :

-blade, mass, balance, edge thickness/angle, nature of primary grind, handle, etc. .

If blades are not overly similar, it is easy to get confounding variables (something else is changing which is causing the effect seen).
Re: Full Height Flat Grinds have weaker V-edge stability
August 04, 2020 10:19PM
The blades I compared were: Flat Grinds:

-Lile Mission in D-2 : 0.24” X 10” X 1.8” (0.030” base per 15 dps 20 dps micro)
-Reground United Rambo II in 420J : 0.22” X 10” X 1.8” (0.025” base per 15 dps 20 dps micro)
-Voorhis Rambo in 5160 : 0.24” X 11.25” X 2.1” (0.020” base per 15 dps 20 dps micro)
-Lile Sly II in 440C : 0.24” X 9” X 1.5” (0.020” base per 15 dps 20 dps micro)

Weights range from 15-17 ounces to 22 ounces on the Voorhis, balance from Neutral on Sly II, 1/2” on United, 3/4” on Mission and 1.25” on Voorhis.

Of all full flat grinds, only the Master Cutlery Rambo held up satisfactorily in flexing thin branches: Similar to the United, but it had a much thicker edge base of 0.040” and 20 dps, with little or no micro.

Sabre Hollow Grinds:
-Colin Cox Survivor in 440C: 0.24” X 10.3” X 1.8” (0.020” base per 15 dps 20 dps micro) one inch Sabre. 25 ounces
-Randall Model 12 in 440B: 0.22” X 8.9” X 1.7” (0.020” base per 15 dps 20 dps micro) 1.25” inch Sabre. 20 ounces.
-Al Mar Special Warfare Aus-6: 0.24” X 7.8” X 1.5” (0.020” base per 15 dps little/no micro) 1.1” inch Sabre. 15 ounces.

Balance ranged from neutral, Al Mar and Cox, to 1/2” on Randall.

The net tally, after much use, is all the flat grinds displayed warped apexes within minutes of use (50 hits or less) , occasionally migrating the warping into the primary grind surface (but never on the D-2 Lile at 0.030” edge base, and only with unstable 2” -3” diameter logs for the others, no migration into the primary with 1/4” branches, although, surprisingly, more flexible 1/4” branches warped the V-edges as badly as the taller warpage, but without migrating into the primary grind).

The 0.040” edge base of the Master Cutlery Rambo held well (the only flat grind exception) while the 0.030” D-2 edge of the Lile Mission displayed little warping but chipped 0.5 mm half circles in rotting 3” logs: The softer outer layer of the rotten logs made the blade less stable and brought out its brittleness... The Voorhis chipped in similar logs but less often, showing more warping instead of chipping, but not migrating into the primary as the United did. United’s 420J has noticeably better fine paper-cutting edge holding than most of the others except D-2, which seemed equal for fine edge paper cutting durability.

All the hollow grinds showed no damage at all with infinitely more loose branch work, only a microscopic wire edge appearing after hundreds of hits. Interestingly, the Full Flat Grinds were equal to Sabre Hollow Grinds in thick stable wood, the poor FFG behaviour only showing up in loose/thin/unsteady branches, in a rather dramatic fashion when edge bases went under 0.030” and especially when nearing 0.020”, only the larger, heavier Voorhis in 5160 being acceptable with such a thin edge base, once a 20 dps microbevel was added to 15 dps/0.020”, but still borderline. Note all the Sabre Hollow Grinds were as thin and showed no sensitivity to unsteady or bending branches.

The difference is quite large and the damage to the apex severe. The striking thing is extensive testing on thick, steady targets completely concealed the vulnerability of Full Flat Grinds when the V-edge was reduced to below 0.030”. 0.040” appearing as a safer minimum to equal the indifference of Sabre Hollow Grinds at 0.020”. With edges far under 0.040” FFGs appear to me as unsuitable for rough use, yet 0.020” edges are far more versatile. I would consider Sabre Hollow Grinds a must for a multi-purpose knife.
Gaston
Re: Full Height Flat Grinds have weaker V-edge stability
August 04, 2020 11:38PM
When you say "warped apexes" do you mean the apex (the very tip of the edge) or the edge bevel itself?
Re: Full Height Flat Grinds have weaker V-edge stability
August 04, 2020 11:39PM
Are those knives reground? Are those measurements the result of a caliper or are they just eyeballed?
Re: Full Height Flat Grinds have weaker V-edge stability
August 05, 2020 09:46PM
The values are based on REK regrind values for the United R2, the Voorhis, the Colin Cox Survivor, the Lile Sly II.

The edge base width values are caliper-based for the Randall Model 12, the Al Mar "Special Warfare", the Lile "Mission", the Master Cutlery R2, On these last four the V-edge angle is eye-estimated compared to the previous 4.

All edge base values were caliper measured and seemed consistent to one another. The Lile Mission was actually 0.028" mostly, but varied a little to around 0.030" at the belly, as the non-two-tone finishes have an inferior grade of surface consistency (which would have been erased had it been fully re-ground by REK: Only the edge itself was done by REK).

I will post here the damage most significant to me: That on the re-ground Taiwanese made United Cutlery Rambo II. It is most relevant to me because this knife, in 420J, had the highest fine-paper cutting edge holding of any knife I ever tested , when chopping into thick stable wood (quite unlike the Chinese made Master Cutlery, also in 420J, which lost its fine paper cutting edge fast, even though it did not get worse afterwards, so otherwise did well): The United held on to a high edge finesse, yet would not create a micro-wire edge in hundreds of hits on thick, stable wood. Only the 440B Randall Model 12 and Lile "Mission" would compare, but the Lile "Mission" eventually chipped badly in unstable rotten wood. The Randall was comparable in fine edge durability, but had this short convex "swell" just above the V-edge, so was not inherently as thin in edge base as the United.

Note the two photos below are after fairly heavy resharpening, which was actually trying to erase cosmetically the damage, but some re-testing was done before any kind of micro-bevel was reapplied. This accounts for the smaller apex damage (which I was trying to avoid carefully during the re-test): What is significant is the edge base misalignment, which is still visible after heavy re-sharpening...: This edge base damage was done on hand-held 3" limbs while being unaware it could happen, but by no means trying to abuse or damage the knife:

[i.imgur.com]

[i.imgur.com]


This knife is significant to me because it performed so well on stable wood. This wide disparity in performance between thick/stable wood and unstable/thin flexing wood seems typical of Full Flat Grind configurations: The stability of the cutting medium seems to be a major issue for these grinds, and it took many years of surprises for me to finally notice and accept the trend: This is in part because Sabre Hollow Grinds are nowhere near so sensitive, even at equally thin edges and angles, so I assumed incidents were flukes: Here are photos of the Lile and Voorhis pulling a similar surprise, years ago, on 3" or more stable or unstable wood, the rotten outer layer of the wood creating the equivalent of unstability for the blade, even when the wood was secured: Noteworthy is that vastly different D-2 and 5160 behaved roughly the same...:

[i.imgur.com]

Note there is considerable warping as well as chipping (but not into primary). The chips tended to appear in close pairs, indicating accidental yawing of the blade: The harder "core" grabbed the edge in one narrow area, the longitudinal yaw inevitably using this "hard grab" as an "axis", putting strain on both extremities of that harder in-core "grab area", but in opposite directions...

As I said, it took me a long while to recognize this as FFG specific. but Sabre Hollow Grinds are definitely nowhere near as sensitive to unstability. What made this behaviour so little known is that it tends to disappear at more "normal" edge thicknesses of 0.040" and 20 dps, OR in thick stable wood, which is probably why few people ever noticed. I do tend to like unusually thin edges for rough work(...), but even the larger Randalls have been delivered this way for decades, and the only complaint I ever heard was for the model 12-9, which may be why this one model has the short convex "swell" just above the V-edge...

Note as well that once I micro-bevelled the larger Voorhis to a 20 dps micro, its behaviour became more reliable (unlike the Lile Mission), even while being flat ground and only 0.020" thick at the edge (the only FFG to be acceptable at 0.020): This I think is simply because being larger and wider, it penetrated deeper, and the apex was thus better protected and less strained laterally. This could explain why the huge Randall "Smithsonian" does not have the "swell" that the Model 12-9 has: For the same reasons, deeper penetration does not require as strong an edge. Or maybe those models are simply never used as hard...

Gaston
Re: Full Height Flat Grinds have weaker V-edge stability
August 06, 2020 03:28AM
How wide are these knives (measurement from apex to spine) :

[imgur.com]

Actual measurement, not a guess.
cKc
Re: Full Height Flat Grinds have weaker V-edge stability
August 06, 2020 04:58AM
Here is an accurate model of a 15dps grind





this knife, maybe I got the wrong knife. is 1.8" height, making the edge 0.11 height claimed 0.03" wide


if this was true and it was 0.03" and 15dps the edge would be 0.058 long, not 0.11 long

by my calculations using the numbers given.. 0.03, and determined 0.11, this lays your edge as almost exactly 15 degrees total, not 15DPS 7.5DPS is the number..

if we assume that the 15dps is accurate and the height is 0.11 approx then the BTE must be 0.056, not 0.030"


no matter what, even with some variance...
the numbers do not match up, and I'm not convinced (same as the last thread) that any of your numbers are accurate.

if it is 7.5dps, not 15.. the damage makes complete sense..

----------------------------------------------------------------------
It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Full Height Flat Grinds have weaker V-edge stability
August 06, 2020 03:12PM
Note that strength, and stiffness are quadratic and cubic with respect to thickness so it is critical that there are exact measurements. As a point of comparison :

-a 12 dps edge has a failure rate which is 50% of a 15 dps one

That angle would be very hard to tell by eye

-a 7.5 dps edge has a failure rate which is 10% of a 15 dps one

That would make the 7.5 dps edge hyper fragile compared to the 15 dps one which be invulnerable on the same work in comparison.

So the first thing I would recommend :

-get actual measurements of the edges otherwise it is very likely there are just geometric differences
-try to get knives which are more similar in other aspects as there are so many confounding variables

ideally, get one of the flat ground knives regound to sabre hollow as that would be a direct test of the hypothesis.

Until then I don't see any evidence for the conjecture which is compelling and I have not noticed it myself in use. I also find the failure pattern odd because :

-15 dps is a very high edge angle
-0.020" is a very low edge thickness

I would not grind a knife like that because everything I have used which would fail there would blow out above the edge bevel because that is a very high angle and low thickness so it would put the failure point beyond the apex and even edge.

Based on what I have seen, it would seem likely to be that those edges are < 15 dps as they have large dents, however some of those steels may also be an issue, I doubt the HT is optimal on 420J2 replicas, not sure with a lot of the others how many of those are actual knives or production copies, etc. .
Re: Full Height Flat Grinds have weaker V-edge stability
August 09, 2020 01:25AM
My knives are not actual knives? Are you being serious?

Let me remind you the United Cutlery in 420J had the best fine edge holding to chopping I’ve ever seen (outside one Randall in 440). I’ve heard low carbide steels have their carbides “melt” into the matrix upon heat treating: Any truth to this? It would explain its superior apex stability on stable thick targets.

I notice you focused on the Lile in D-2, despite this not being listed as being precisely REK reground: It was indeed 0.028” thick on the calipers, but you cannot estimate the edge angle on a hand re-grind, especially with this diabolically hard to sharpen steel, despite my fresh coarse diamond hone (combined with the irregular edge thickness typical of the Lile shop’s workmanship)...

Even in the picture, you can plainly see the Lile edge is not one flat surface, but has two surfaces in it, plus a rounded transition. Measure halfway of 0.11” and you are barely there...: 0.055” is pretty close to the correct figure you quoted. Not a great edge cosmetically, but a damned hard steel to work with...

Let me be clear: I KNOW what 15 dps is... It is childishly simple to estimate, visually, its exactly 2:1 ratio, and it has been my target angle for 30 years. You tried to put this in question on the Busse, and it backfired on you when REK showed it to be closer to what I was saying than to your estimations from photographs.

Questioning whether these are real knives or halving the angles to obviously crazy figures, having never handled the knives, is not serious. Furthermore, all these knives were changed to numerous angles and re-tested continuously over years on end (not to mention always sharpened cold...). I did not want to see a $2000 RJ Martin Blackbird in S30V continuously make a micro-burr in one hit over two years at 20 dps, but it did... I did not want to see a $2000 Lile Mission chip, over years, on unstable or rotting wood. Or a $1500 Sly II in 440, a $500 Voorhis in 5160, warp on thin flexible branches, but they did...

I thought I had finally found something more reliable in a United Cutlery in 420J (better than all the other flat grinds on stable targets, outside the Voorhis, yet much better than the Voorhis at not making micro-burrs). Unfortunately, even that proved vulnerable to careless handling on unstable targets...

I’ve seen Sabre Hollow Grind fail because of inferior steel, but even that was rare: The only prominent example I can think of was an oddball enlarged Buckmaster clone made in Japan, called the Parker K-633 or something similar... The edge dented easily. Other than that, I have never seen any Sabre Hollow Grind do anything worse than fast micro-burrs, like the $2000 RJ Martin in S30V. By contrast, ALL Full Flat Grinds choppers ended up with severe edge damage at one time or another, the only one to escape this rule having a 0.040” edge base at 20 dps: A Master Cutlery R2 destruction tested (pounded all the way through 8” logs) over two years, surviving intact where a brittle Lile I am sure would have ended up in several pieces... The MC was a bit thick edged, but the best most indestructible FFG I have seen so far...

This is from years of testing over many knives: The notion Sabre Hollow Grinds are somehow less optimal for hard chopping use is just the mind considering things theoretically, and then ignoring, perhaps not even testing, easily observable reality. Randall did not settle for no reason on Sabre Hollow Grinds for big choppers. The huge emphasis on other grinds is a step back from that, just like people measuring from photos thinking they know better than the person actually holding the knife.

Gaston
cKc
Re: Full Height Flat Grinds have weaker V-edge stability
August 09, 2020 06:29AM
Quote

Let me be clear: I KNOW what 15 dps is... It is childishly simple to estimate, visually, its exactly 2:1 ratio, and it has been my target angle for 30 years. You tried to put this in question on the Busse, and it backfired on you when REK showed it to be closer to what I was saying than to your estimations from photographs.

nothing backfired at all.. the evidence was absolutely in favor of you being wrong. REK clearly showed that it was nothing like what you said. you read things, but you are not taking them in. you are taking in whatever you think helps your statement.

you are doing the exact same thing here, with the same knives, which are all in question. not a single thing you have shown provides anything except annectodal information that cannot be backed up;

that's ok. its your life and your knives, but to try and convince others of what you are saying needs a lot more effort.

you are making a claim similar to "water floats on oil" and asking the world to just believe you based only you saying it happened to you.
go for gold. i spent enough time on the last thread. this one, I'm just going to follow and see where it goes.

It doesn't effect me in the slightest if you have some weird phenomena in knife use that only effects you.

Quote

My knives are not actual knives? Are you being serious?
who are you even talking to? quote something specifically that someone claimed your knives are not actual knives?

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It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Full Height Flat Grinds have weaker V-edge stability
August 09, 2020 06:49AM
Like Staley and the boys said:

“Into the flood again, same old trip it was back then.”

It might be interesting to consider a few questions that Same Harris once asked:

“All we can do is appeal to scientific values, and if he doesn’t share those values, the conversation is over. If someone doesn’t value evidence, what evidence are you gonna provide to prove that they should value it? If someone doesn’t value logic, what logical argument could you provide to show the importance of logic?”
cKc
Re: Full Height Flat Grinds have weaker V-edge stability
August 09, 2020 08:12AM
Exactly. but im too tired to go do it 2 times. someone else's turn. this topic doesn't have a lot of interest to me. it is an extension of the other one, not a new one

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It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Full Height Flat Grinds have weaker V-edge stability
August 09, 2020 09:09AM
I feel ya. We thought we were beating a live horse, but it turns out that it’s been dead for years.

This does go to show, however, that although some of what I say and some of the judgement calls I make seem rather harsh or perhaps made too quickly, I’m often onto something. Sometimes it can be useful to have a mean dude around as long as the meanness is just a byproduct of what he’s actually driving at.
cKc
Re: Full Height Flat Grinds have weaker V-edge stability
August 09, 2020 09:59AM
i would replace mean with critical though, and try to not let it ever be personal. tear apart the data. that was my main point

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It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Full Height Flat Grinds have weaker V-edge stability
August 09, 2020 02:26PM
Quote
Gaston444
My knives are not actual knives? Are you being serious?

I don't know what it would mean to say they are not knives, however they are not measurements. The failure point is nonlinear with angle, just a TWO degree difference either way, one knife which is one degree higher, and the other one degree lower than what you think will make one knife fail at HALF the point of another.

This isn't the place to promote theories without evidence, there are lots of other forums for that.

As for

Quote

I’ve heard low carbide steels have their carbides “melt” into the matrix upon heat treating: Any truth to this?

All steels when austenized will have the primary carbides (those that form in the original melt) start to dissolve, the properties of the steel comes from the alloy content and thus it needs to be in the steel (not in the carbide) in order to have those properties. How much of the carbide remains depends on how it is austenized. In general yes, low carbide steels have less carbide in them after the heat treatment, but it isn't because the primary carbides dissolved, that always happens, it is because there was less there to begin with.


Quote

This is from years of testing over many knives

A lot of anecdotal evidence is still anecdotal evidence.

Kyley and Ryan, this isn't the place for personal commentary on Gaston.
Re: Full Height Flat Grinds have weaker V-edge stability
August 09, 2020 08:51PM
Is it possible to see a picture of all of those knives together?

I am not familiar with the models, and I would like to see what exactly is being grouped. It is possible to do multi-variate analysis and reach a conclusion (my MSc thesis did that) BUT they are insanely complicated and prone to confounding variables.

Just off the top of my head, you could see influences from :

-handle type
-steel
-size/weight

etc. .

Dan Keffler wrote about the influence of handle type significantly, he was one of the first makers I know to really treat it seriously. He has a background in that field and when he first started cutting he noticed how significant the handle was to control of the blade and how that in particular influenced cutting ability and durability.

A few simple experiments can really reduce that, one would be to simply get someone to hollow grind one of the flat ground blades and see if that dramatically increased the durability. Or do a simulation, something like :

-put both blades in wood
-subject them to a a side load until failure

See if the hypothesis holds. Because you can normalize the side loads and penetration, you can remove a lot of the confounding variables. You might have something interesting, but you need data otherwise you just have conjectures. Now to be clear science always starts with conjectures, nothing wrong with that.

As a side note, I have little use for hollow sabre ground chopping blades because :

-low durability to weight ratio
-shallow penetration
-very high binding

and this is the more controversial part, they are usually on blades which have strong fantasy designs, not practical using types. I have used some very high end ones (expensive is all I mean there) like Strider/Reeve, as well as cheap productions and they all behave the same.

As another point of consideration, it isn't like the guys doing Bladesports can't use them, but ask them why they don't run shallow sabre hollow grinds and they do a LOT of chopping in the competition.

Try this :

[www.youtube.com]
Re: Full Height Flat Grinds have weaker V-edge stability
August 10, 2020 05:44AM
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cKc
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Let me be clear: I KNOW what 15 dps is... It is childishly simple to estimate, visually, its exactly 2:1 ratio, and it has been my target angle for 30 years. You tried to put this in question on the Busse, and it backfired on you when REK showed it to be closer to what I was saying than to your estimations from photographs.

nothing backfired at all.. the evidence was absolutely in favor of you being wrong. REK clearly showed that it was nothing like what you said. you read things, but you are not taking them in. you are taking in whatever you think helps your statement.

This is how it went down:

You claimed, on the thread “A few Hollow Handle knives”, on the April 27 post at 09:18 PM, and this AFTER REK said he could not find any of my Busse convex figures (leaving you in the clear to cobble up calculations from photographs) that my Busse COULD have been as thin as 6-8 dps. Pretty much similar figures to what you did on this thread...

You then misinterpreted the micro bevel I put on the nearby Voorhis as being possibly the main original re-ground edge at 11 dps on 0.020”, claiming, based on this, that the Busse must be at a SUPREMELY THIN angle...

Unfortunately for you, REK later came back, on May 02 at 6:22 AM, with figures and photos of the repaired Busse, whose overall appearance (and Ricasso depth) looked NEARLY IDENTICAL to the pre-damage photos I posted, and the figure he quoted was 20 dps... I was honest enough to concede the original grind could have been as low as 15 dps but no lower.

This did conclusively prove your absurd April 27 tentative claims of something near 6-8 dps or of “SUPREMELY LOW ANGLE” were not even in the ballpark, and since I was the one handling the knife, the least you could have done is 1- Recognize that your own estimates were vastly off, and 2- Display the courtesy of taking my own estimates at face value.

Gaston
Re: Full Height Flat Grinds have weaker V-edge stability
August 10, 2020 01:43PM
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Gaston444


nothing backfired at all.. the evidence was absolutely in favor of you being wrong. REK clearly showed that it was nothing like what you said.


Gaston,

Please do not paraphrase what other people said, post a link and use direct quotes :

[www.cliffstamp.com]

Quote
="REK"

These are the pics of the battlesaw I took for ebay after I fixed the damage - sorry I didn't get any before pics or take measurements unfortunately, so there is a lot of uncertainty about angles. I think for the small secondary bevel I took it to 20 dps though.

He notes he "thinks" the small secondary bevel is 20 dps, again no measuring.

Kyley didn't "cobble" edge measurements, as he did in this thread, he went from known blade measurements and scaled a picture, this is just math. The only way to dispute it is by disputing the figures he used for the blade height.

You are the one making claims without measurements, and coming to conclusions which are fairly radical, and refusing to provide simple data on knives, again this isn't the place for that - there are lots of places that will indulge that, please go there.

If you want to throw out radical ideas, sure, but if you are not willing to engage in criticism of said ideas and provide supporting data - well there are likely better forums for that than this one.



Edited 1 time(s). Last edit at 08/10/2020 05:59PM by CliffStamp.
Re: Full Height Flat Grinds have weaker V-edge stability
March 13, 2021 08:20PM
He did not even know the most basic fact of all, the edge thickness at any given height: Everything else was per force speculation, and you say he started from known elements because he had the height, alone, from a photo!

I sure hope you see the problem here... I held the knife in my hand and examined it over hours: It would have easily swallowed up the Voorhis cross-section of 0.020" edge thickness and 12 dps from the very apex all the way up. The Battlesaw had a thicker edge and a more open angle than the 12-dps of the Voorhis, which later survived quite well with only a bit of micro-bevel. I had most of the facts and he was speculating from photos, with not the slightest thickness data point. Surely measuring from another knife doesn't count, I hope...

Furthermore, it is obvious convex edges can generate more lateral pinching forces, nearer to the apex, from the point of view of the wood's ability to generate a "wood pressure grip" (compared to a hollow grind at least), so it is not solely an issue of the steel, and I did say so.

Full Flat Grinds also generate a higher "wood pressure grip" near the edge (compared to a hollow grind), and this can also damage the apex from slight lateral movements: I have experienced this. But this happens from the broadness of the wood's friction, the hold being due to the broader surface, not its intensity of pressure, so the effect is different and less severely focussed than on a thin convex edge. Although higher pressure on a narrower height focus does allow easier edge twist-retrieval for the convex (good for competitions), the convex cannot prevent multiple warping unless significantly thicker overall, which was the case on the Battlesaw, and yet even that was still not enough to avoid severe multiple two-directional warpings. The Battlesaw was so thick it was barely flesh slicing capable, so its failure was the immediate end of the story for me.

I certainly do regret not calipering it throughout the height, with photos somehow, as this would have ended the debate. Though I wonder now, as next in line would have been measurements of the exact amount of lateral force I put in that would have created the photos I posted. What if I applied little to no lateral forces on the Voorhis? Without calibrated lateral forces, how do we even know this is a valid observation? And so on and so on...

I did note since a significant difference in chopping through hand-held or knee-stabilized wood, with one very slight warp happening on a Full Flat Grind United Cutlery, at 0.025" on 12 dps with no micro, due to the long heavy overhanging wood twisting down as the chopped area thinned, this causing a powerful twisting compression into the edge of the wood-trapped blade, as the heavy unsupported overhanging piece twisted down, with the blade still trapped at the junction... This was the first damage on this 420J knife I had seen in YEARS of use, and it was barely visible... I believe in the value of keeping things simple: The Battlesaw failed multiple times in MINUTES, and I provided the photos. Somehow the same things keep happening in the same way, but we are not allowed to draw conclusions: Not scientific enough. Jonathan Swift was making fun of this three hundred years ago.