Scandi edge?

[canid]

yes. i'm saying that the actual convergence angles being equal, the edges themselves will wear at the same rate.

the 'meat' behind them influences the bevel integrity, not the edge.

the only thing reducing the bevel angle does is to reduce drag, as the width to length ratio of the wedge decreases with distance from the edge.

[JCavSD]

Here's a decent drawing of the various grinds for comparison.

Guests can not see images in the messages. Please register in the forum.

[JCavSD]

yes. i'm saying that the actual convergence angles being equal, the edges themselves will wear at the same rate.

If I'm understanding you correctly...if the grinds are at the same angle, then it's a wash? I think that's the point though...different grinds favor different angles. The "convergence" angles are typically not equal.

[Rick]

@ JGCoasty - That was true at one time. Today, Mora is the name of the company after the merger or Erikkson and Frosts, both of whom made knives and both of whom were from Mora. If you say Mora today, you are talking about the company, Mora of Sweden.

http://www.moraofsweden.se/index.php?id=7

[jgcoastie]

@ JGCoasty - That was true at one time. Today, Mora is the name of the company after the merger or Erikkson and Frosts, both of whom made knives and both of whom were from Mora. If you say Mora today, you are talking about the company, Mora of Sweden.

http://www.moraofsweden.se/index.php?id=7

Ahh... Now I get what you were saying. How could I have missed that??? Sorry big guy.

[Rick]

Well, you took a left at Finland and got stuck with those danged Puukkos. If you had stayed on the main road then........

[canid]

would you believe i know what a knife grind is.

more specifically, i also know what an edge is, what a bevel is, and how they work.

an edge is nothing more than an abstract line segment. for a given intersection of n-faces, the edge is the point at which they converge. any discontinuity in this segment results in the creation of futher faces, and the formation of additional edges.

cutting ability is created by action of shear stress of one or more edges [tangential?] to a solid face.

very roughly speaking, the resistance to cutting should be a product of the shear strength of the solid, the length of all edge segments in contact and the coeficient of kinetic friction of the faces in contact [ increasing with the surface area of faces in contact with the face to be sheared].

now; since the shortest distance between two points is a line segment, the fewer discontinuities in an ideal edge segment, the lesser the length of the total edge segments, and the lesser the surface area of faces in contact with the solid to be sheared.

because solids to be cut are elastic, and deform to one degree or other with the application of force, the rate at which the surface area and lengths of edge segments increases for a given degree of deformation can be minimized by changing the angle of bevel as you move back from the edge [which we've established is actualy a number of edge segments connecting many faces]. this is what i mean by reducing drag.

singe the edge itself is only an abstract segment, the angle of convergence is broken by any discontinuity, ragardless of whether the edge angle is 90°, 45°, etc. the mass behind it determines the forge required to deform it by a given amount, but the force required to deform it at all is pretty much the same.

it should be noted that i am essentially not college educated, and am largely self taught. i am only giving you an explanation of an aspect of mechanics to the best understanding and ability. how you choose to take it is entirely up to you. you've already got your own education and understanding, and i acknowledge that.

[canid]

the overriding point here was that the blade geometry effects the structural integrity of the faces, and the mass they define directly, and the edge properties and friction of cutting action only indirectly, with friction being the greater factor.

[JCavSD]

would you believe i know what a knife grind is.

more specifically, i also know what an edge is, what a bevel is, and how they work.

an edge is nothing more than an abstract line segment. for a given intersection of n-faces, the edge is the point at which they converge. any discontinuity in this segment results in the creation of futher faces, and the formation of additional edges.

cutting ability is created by action of shear stress of one or more edges [tangential?] to a solid face.

very roughly speaking, the resistance to cutting should be a product of the shear strength of the solid, the length of all edge segments in contact and the coeficient of kinetic friction of the faces in contact [ increasing with the surface area of faces in contact with the face to be sheared].

now; since the shortest distance between two points is a line segment, the fewer discontinuities in an ideal edge segment, the lesser the length of the total edge segments, and the lesser the surface area of faces in contact with the solid to be sheared.

because solids to be cut are elastic, and deform to one degree or other with the application of force, the rate at which the surface area and lengths of edge segments increases for a given degree of deformation can be minimized by changing the angle of bevel as you move back from the edge [which we've established is actualy a number of edge segments connecting many faces]. this is what i mean by reducing drag.

singe the edge itself is only an abstract segment, the angle of convergence is broken by any discontinuity, ragardless of whether the edge angle is 90°, 45°, etc. the mass behind it determines the forge required to deform it by a given amount, but the force required to deform it at all is pretty much the same.

it should be noted that i am essentially not college educated, and am largely self taught. i am only giving you an explanation of an aspect of mechanics to the best understanding and ability. how you choose to take it is entirely up to you. you've already got your own education and understanding, and i acknowledge that.

I believe I understand your point now, and it's quite possible that we're debating semantics. Thanks for putting in the effort to explain your thoughts.

[Sourdough]

Mora knives:

Cheap!
made with good steel
very durable
Cheap!
come very sharp
easy to resharpen
and they are very cheap!

best $10 blade on the market, hands down, and probably better than most knives in the $50 range.

Yes, the only thing I would add is that they are in-expensive. If I ruin a $16.00 Mora on a construction job, I just shrug it off. If I ruin a $400.00 custom knife, me not happy. I look at the Mora as a very good, but disposable tool. And CHEAP.

[klickitat]

Here's a decent drawing of the various grinds for comparison.

Guests can not see images in the messages. Please register in the forum.

Here is where I respectfully disagree with you. The only picture that has a different edge is your picture of the scandi edge. All the other pictures are pictures of convex edge grinds and/or short scandi edge or variations of such.

A true concave or hollow ground edge, such as on a straight razor have the hollow grind converge on the edge itself and is the sharpest but most fragile of the edges, because it has absolutely no shoulder to support the edge.

The scandi grind is a single angle with minimal shoulder to support the edge and is second for edge holding ability.

The convex edge gives the best support shoulders for the edge and will hold an edge longer than the others in a heads up test.

The Tri-edge grind with 3 successive steeper angles is the easiest way of producing a sudo-convex edge and is as durable, but produces more drag than a true convex edge.

The ABS has done extensive testing on this and is backed up year after year in the sharpest knife competition.

[RichJ]

Yes, the only thing I would add is that they are in-expensive. If I ruin a $16.00 Mora on a construction job, I just shrug it off. If I ruin a $400.00 custom knife, me not happy. I look at the Mora as a very good, but disposable tool. And CHEAP.

I paid $12 (shipped) for a 780 a couple of years ago and it came scary-sharp. I've used it a bunch as an all purpose camp knife and the edge is still incredibly sharp. I'd say I've lost only about 15% of the original sharpness because I can still shave my arm clean with one pass. I haven't babied it at all other than putting a little 3-in-1 oil on it when I put it up to keep the rust off.

[Rick]

Try some food grade mineral oil and you won't have to worry about getting 3-in-1 oil on meat or food.

[Pocomoonskyeyes3]

Here's a decent drawing of the various grinds for comparison.

Guests can not see images in the messages. Please register in the forum.

This is what I also use to illustrate the different grinds. A "Grind" Is how the cross section(As seen above) looks when the actual Grinding of the blade is finished. The different "Grinds are more for the "Toughness/Durability" of the actual edge. I wouldn't put a Convex on a straight razor, nor would I put a "Scandi"/Flat grind on a chopper. True both can be made scary sharp, but what is the intended purpose? Hard heavy work, or fine delicate cuts?

would you believe i know what a knife grind is.

more specifically, i also know what an edge is, what a bevel is, and how they work.

an edge is nothing more than an abstract line segment. for a given intersection of n-faces, the edge is the point at which they converge. any discontinuity in this segment results in the creation of futher faces, and the formation of additional edges.

cutting ability is created by action of shear stress of one or more edges [tangential?] to a solid face.

very roughly speaking, the resistance to cutting should be a product of the shear strength of the solid, the length of all edge segments in contact and the coeficient of kinetic friction of the faces in contact [ increasing with the surface area of faces in contact with the face to be sheared].

now; since the shortest distance between two points is a line segment, the fewer discontinuities in an ideal edge segment, the lesser the length of the total edge segments, and the lesser the surface area of faces in contact with the solid to be sheared.

because solids to be cut are elastic, and deform to one degree or other with the application of force, the rate at which the surface area and lengths of edge segments increases for a given degree of deformation can be minimized by changing the angle of bevel as you move back from the edge [which we've established is actualy a number of edge segments connecting many faces]. this is what i mean by reducing drag.

singe the edge itself is only an abstract segment, the angle of convergence is broken by any discontinuity, ragardless of whether the edge angle is 90°, 45°, etc. the mass behind it determines the forge required to deform it by a given amount, but the force required to deform it at all is pretty much the same.

it should be noted that i am essentially not college educated, and am largely self taught. i am only giving you an explanation of an aspect of mechanics to the best understanding and ability. how you choose to take it is entirely up to you. you've already got your own education and understanding, and i acknowledge that.

Can you translate that into Layman's English?

Here is where I respectfully disagree with you. The only picture that has a different edge is your picture of the scandi edge. All the other pictures are pictures of convex edge grinds and/or short scandi edge or variations of such.

A true concave or hollow ground edge, such as on a straight razor have the hollow grind converge on the edge itself and is the sharpest but most fragile of the edges, because it has absolutely no shoulder to support the edge.

The scandi grind is a single angle with minimal shoulder to support the edge and is second for edge holding ability.

The convex edge gives the best support shoulders for the edge and will hold an edge longer than the others in a heads up test.

The Tri-edge grind with 3 successive steeper angles is the easiest way of producing a sudo-convex edge and is as durable, but produces more drag than a true convex edge.

The ABS has done extensive testing on this and is backed up year after year in the sharpest knife competition.

So which grind wins most often? For How long does the edge last? Do you have a link so I can see the results of these tests?

Try some food grade mineral oil and you won't have to worry about getting 3-in-1 oil on meat or food.

Vaseline/Petroleum jelly will also work as well, is much easier to find and has more uses I think, While being just as safe to use around food. I have yet to find any food grade mineral oil in any of the stores I frequent..... maybe I just don't know where to look.

[crashdive123]

Poco - look in either a drug store, or the pharmacy section of your grocery store.

[Rick]

Nothing wrong with PJ at all. Good suggestion. Either one will keep from fouling your food.

[Camp10]

Poco - look in either a drug store, or the pharmacy section of your grocery store.

or the cooking section at walmart, etc. Look around where they sell cutting boards and wooden spoons.

[klickitat]

I used to have a copy of the rules for the competition but since the move I have no idea where they are at.

However I can give you an idea of some of the contests.
#of cuts in 1" hemp rope after hacking so many times in a 2x4. How many soda cans can be cut. I think there was something about sticking apples in a tank of water too.

I do not remember it all. I got a copy of the rules years ago and was thinking about entering, but never did.

[Camp10]

I used to have a copy of the rules for the competition but since the move I have no idea where they are at.

However I can give you an idea of some of the contests.
#of cuts in 1" hemp rope after hacking so many times in a 2x4. How many soda cans can be cut. I think there was something about sticking apples in a tank of water too.

I do not remember it all. I got a copy of the rules years ago and was thinking about entering, but never did.

One cut through a hanging 1" hemp rope with one swing

2 cuts through a 2x4 and still being able to shave.

the blade is then placed in a vise with about 2/3 left out and bent at least 90° without breaking. It can crack up to 1/3 it's thickness but cant break. If any part of the edge chips or breaks at any point in the tests (other than the bend) it has failed and the test is over.

Edit: sorry, these are the skills for a master smith's test knife.

[canid]

Poco: in short; the edge and the grind are two completely different things.

in those photos, the edge is only the exact point at which the two bevels converge. it is made up of countless smaller edges and it is their scraping action which causes a cut. the only impact the rest of the bevel has on cutting is how much friction it imparts to the material being cut [basically how much of it's surface area is in contact while the edge is cutting].

other that that [which is important, but takes a back seat to edge efficiency], the benefits of one grind to another are only matters of structural integrity [resistance to impact].

there's nothing wrong with semantics. semantics is the study of meaning, and to express an idea well, what we say must describe what we mean, and what we mean must describe what is, to the best of our abilities.