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Scandi, just how good are they?
- Thread starter Temper
- Start date
Yes, looking at them again the full convex is very fine at the edge, probably half of that of the hollow ground.
So, I am thinking of about 4mm 3V what height would you guys suggest for the grind? I am thinking of about 30mm for the depth of the blade and at least 10mm for the grind with a final angle of about 30 deg (inclusive)
Formula- half thickness / grind height = tan (edge angle)
2 mm thick per side divided by tan of 15 degrees per side = 7.46 mm bevel.
10 mm bevel will give you an angle of 11.3 per side.
To get a 10 degrees per side, you need a bevel of 11.3 mm. (It's a coincidence the numbers are reversed)
By the way, the one you describe sounds like a Ka-bar too me, if you flatten the secondary grind to the primary grind.
2 mm thick per side divided by tan of 15 degrees per side = 7.46 mm bevel.
10 mm bevel will give you an angle of 11.3 per side.
To get a 10 degrees per side, you need a bevel of 11.3 mm. (It's a coincidence the numbers are reversed)
By the way, the one you describe sounds like a Ka-bar too me, if you flatten the secondary grind to the primary grind.
Cliff Stamp
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Temper said:
Many production hollow ground knives are like that hence the perception in general that they cut poorly, not the fault of the grind, just the way it is used. Krein does really thin hollow grounds that show the true nature of the grind s does Johnston but he doesn't sell anything and does no public promotion.
kel_aa said:
It doesn't frustrate me, it is natural behavior, I understand it and expect it. I watched Alvin go through it heavily on usenet and generally to a more harsher responce because usenet it not moderated. The internet isn't a private conversation, it is essentially a public debate with a very wide audience, that is who I am speaking to in threads like these, simply providing facts for those that want to see them.
-Cliff
Okay, you are well tempered then. 550 F for 4 hours? So you can say it in simple terms. You can say it in engineering terms. You can name people who support similar views. And then what? What more can you do against those who think their experience is uniquely justified?
Cliff Stamp said:
I think the humorless and breathtaking lack of humility in statements such as this is one of the reasons people sometimes get their back up. People prefer to engage in conversation and not be lectured at by some kind of self proclaimed knife messiah.
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North61 said:
Is the implication that the other is wholly responsible for how YOU react to what the other communicates and how he communicates it? Is this not a shared responsibility if the objective is communication?
Further, there are substantive disagreements that emerge in these threads. But not everyone wishes to marshall facts (diplomatically or otherwise). A classic, common tactic in dealing with a position with which you disagree is to attack the opponent, finally degenerating to name-calling. (I recalll the Saturday Night Live point-counterpoint bit with Dan Akroid and Jane Curtain (sp?). Akroid would often begin his responses with, "Jane, you miserable slut . . . ." )
I surrender.
But if you look at transactional analysis it is a truism that when someone comes off as the parent figure (the authority) it brings out the child in others.
There is an attitude in some of Cliffs posts that does make me want to tweak his nose. My Bad.
But if you look at transactional analysis it is a truism that when someone comes off as the parent figure (the authority) it brings out the child in others.
There is an attitude in some of Cliffs posts that does make me want to tweak his nose. My Bad.
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North61 said:
I had this algebra teacher once . . . . . .
Temper said:Coolio! Thanks!
Does anyone know what the specs are for the Woodlore knife? I'm interested to see how it would compare to the one I am thinking about.
Blade length is 4 1/4"
Handle 4 1/2" Birds Eye maple
Maximum width of blade is 1"
Blade thickness 5/32
01 tool steel (can't remember what RC but around 59 I think)
Single flat bevel at 16 degrees. This was very slightly hollow when new due to being ground on a large diameter wheel: much less hollow than found on EKAs though. After a few good sharpenings on Edgepro, it is now flat and works very well.
Cliff Stamp
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kel_aa said:
The experience is justifed, I had the same experience and reached the same conclusions. When I first used that style of knife the cutting ability was among the best I had seen for wood working and rope cutting and for a time my perspective on that geometry was very positive as I attributed the performance to the nature of the grind. It didn't however take very long to realize that was flawed and what I was seeing had nothing to do with the nature but the implementation, specifically the acute angle of the edge.
This came out of work mainly done by Swaim and commentary by Johnston as well as discussions with makers like Wilson and Sorg. Lee covers the same issues in some detail as well in his book, as does Cook and J.J. of Razor's Edge. You see the same basic underlying fundamentals in all of them. J.J. relief grind on meat knives follows the same general principle behind Cook's prefered grind on hardwood axe heads. Sorg was a convex grinder mainly, Johnston hollow and Wilson flat, but the same *general* performance principles are found in all of their knives, just ignore the type of grind and consider the specifics of implementaion.
Spuddate said:
That's the goal. You might want to scan rec.knives for Swaim's work, much of what I do was based on work he did. He has moved on past knife work as a hobby but he produced a huge body of comparative work covering the influence of geometry on cutting ability and edge retention as well as profile and balance for chopping. As well of course ergonomics and grip security, sharpening, corrosion resistance, etc. . I have been collecting it lately and plan to recap it in a webpage.
-Cliff
But the experience is not justified in the right context. I think all it takes is to look in your kitchen. Most of us here have cooking experience. Weight handling/flexing issues aside, thinner (at any distance away from the edge) knives cut better in so far as you are cutting a semi-binding material that deep. Should that be a theorem in the knife world? (We have a 9 in (2 inches wide) or so kitchen knife that is about 1 mm think. It gets a little hairy if you use that to cut large root products like rutabegas.) Then you look at the bevel and shoulders of a Scandi grind. That is definately not thin. Then you have to accept that every possible advantage of having any part thicker comes at the price of decreased cutting ability as far as cutting (deep cutting, to be consistant with the above) is concerned. No experience can tell you that having more metal makes it cut better. (Again, not considering weight balance/flexing/splitting action...)
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I always love to hear the experiences of folks who actually use their blades a lot for stuff ( like Cliff)
Cliff Stamp
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kel_aa said:
It is justifed often by the experience of the users who are often not looking to challenge it which is the major problem.
With the addition of "as long as the reduction in cross section does not induce more binding by passing the critical limit of the materials resilence which reduces wedging by fracture." The easiest example of this is a splitting axe, but the same basic principle can be seen in other materials. If you cut carrots for example with a very thin knife and a very thick one and then use the same to cut a pile of rhubarb the force ratios will be much closer on the carrots. Even though the carrots wedge much heavier the resilence is much lower. In some cases I have seen this actually make the cutting worse for the thinner blade, but generally you can avoid this with use of hollow reliefs and other aspects like distal tapers and multi-bevels.
[kitchen knives]
Yes, and that is how the really cheap stamped kitchen knives are ground and everyone knows they are generally inferior. As I noted earlier, if you take the same general principles being discussed and remove the scandinavian label from the discussion there would be little debate. Consider for example the common fact repeated endlessly that as edges thicken and become wider it is necessary to rework the primary grind to compensate for the loss in cutting ability and ease of sharpening. Now apply this presupposition to a comparison of full flat vs scandinavian style blades. How long would you have to hone a Deerhunter at 10 degrees before the edge would thicken to the point it would look like a scandinavian blade. Now who would argue that as the edge thickens and widens the cutting ability is improving?
If you look at it critically yes, which is why makers like Wilson will never use them.
-Cliff
Resilence is the abiltiy to elastically compress? Are we saying that it is easier/at least helps to fracture the carrots than to cut it? I can agree with that:
About the kitchen knife, I wasn't making a comment on its quality or price. Just that it is so thin that it it may be counterproductive or unsafe (in terms of how much it flexes) on some materials. Chinese style cleavers, on the other hand, are about that thin but due to the wide blade edge to spine (4 inches?), it doesn't flex much at all. But then the width of the blade is restrictive in other uses...
Cliff Stamp
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kel_aa said:
To rebound from strain. Once you pass it the material won't induce a binding force because it "wants" to stay in the deformed position anyway. A rigid material with a high resilence is hard to cut because it takes a lot of force to push it apart and it snaps back very hard around the blade as the knife passes through it. On deep cuts into hardwood for example you can see some woods actually fold back across the spine of some blades and grab the knife hard. On them you can't go too thin or you will never get the knife out after a cut. This then leads to the hollow grinds on axes which is the same principle behind the hollow grinds on japanese utility knives. Even though the materials and methods used to cut are really different, the same basic types of forces are at work and they guide similar designs.
Yes exactly, this cracking can reduce the binding and offset the general reduction in cutting ability due to cross section. I noticed it when comparing the Mora 2000 to a bunch of full ground knives on various binding materials like vegetables, cardboard, styrofoam and splitting woods. The flat ground blades of thicker stock but with thinner edges could go into the material much easier initially and then have less binding on the primary due to wedging as the Mora will bind heavily on the flats as machetes do, which are the same grind, and again it is commonly known this is a problem with them on deep cuts into such materials.
Yes, as with all designs, if you focus on one element you will give up performance elsewhere. Rigidity as with any element is always needed to some degree, if a blade had noneit would bend when you picked it up under its own weight. Some machetes are actually close to this level and will flop around readily with light wrist action. Some blades need to flex and others you want infinite rigidity.
Yes, torque comes into play strongly which is why blade width has a negative aspect however a wider blade on a given stock also allows a thinner profile which is a positive and these two countering forces mean there will be some "sweet spot" where the performance maximizes, a common behavior whenever an attribute has opposing influences. Paring knives out of 1/16" stock for example can be a half an inch wide and still cut very well because the primary angle is still low. To get the same primay angle on 1/4" stock you need four times the width, hence the common 2" width for the "magic" 3/5 primary bevel angle common on so many generally regarded high performance knives. If you make the thicker blade more narrow it can turn better in cuts due to less counter torque and you will notice this stability when carving but you have also made the profile more obtuse and thus the wedging resistance is higher and it takes more force to drive it into the cuts. Cook also talks about another aspect of wide blades in the axe book in regards to accuracy of cuts which has relevance to some knife use.
-Cliff