sharp vs ultra-sharp

[manassas dragon]

not having done an actual test-but it seems to me that a knife sharpened
with a very fine polished edge will not stay sharp as long as the same knife sharpened to a toothier edge. the toothier edge might cut longer than the finer edge.

that is to say that the toothier edge will not be as sharp initially, but will still cut acceptably for a longer time than the finer edge.

am i full of it,or is there anything to this? like i said, i haven't seen or done any actual testing.

 

[Carl_First_Timer]

Would imagine the "toothier" aspect works as tiny serrations.

 

[Stacy E. Apelt - Bladesmith]

Apples and Oranges.
The polished fine edge is great for fine slicing, but won't take abuse. The "toothier" edge will not slice as well, but will last longer.
They would have to be tested by different standards.
Fine edge - slicing tomatoes and shaving hair.
Toothy edge - cutting rope or butchering a deer.

 

[me2]

The toothy edge, though not as sharp as the polished edge, will stay at about the same level of sharpness for a long time. The polished edge will degrade fairly rapidly, but not nearly as quick as most people think. After an initial loss of sharpness, the polished edge will level off and dull much slower than at the beginning. This probably leads to a perception that a very sharp edge dull quickly, when all it has actually done is degrade to the point the toothy edge started with. At this point, they both will stay at this level for a long time. With the polished edge, you get the initial period of extra cutting.

 

[Jeremy Horton]

Well I must be doing something wrong

 

[Rick Marchand]

In a soft medium like food prep and game dressing(aside from bone breaking) I could see how the toothy edge would allow you to cut longer even when dull. I call that "Ginsu Sharp" because it is nothing more than a fine saw... it serves a purpose.

The highly polished edge with proper geometry will stay sharp longer than a toothy edge. There is no getting around that. Some folks imagine a polished edge to be as thin as a razor. Well the razor guys (Butch) will tell you that there is a big difference between razors and field knives when it comes to geometry.

Every one of those ridges that comprise a toothy edge are prone to dammage. they are unsupported "hangnails" that are only good for draw cuts. Any contact with hard material will begin rounding them off. With a polished edge, there is nothing to "catch" on... no singled out weaknesses... the edge works as one unit.

Like Stacy says... apples and oranges. You tune you edge to suit the use. They both have their advantages and limitations.

... but super sharp is still better... HA!



Rick

 

[Jeremy Horton]

I thought with proper geometry. You could have both

 

[Tippet]

IMHO a 'toothy" edge is improperly sharpened. It may cut very well, for a little while; so might a wire edge. But very quickly you're dealing with a dull blade. Meanwhile one that's sharp from the beginning cuts better and lasts longer. How much longer depends on the steel.

 

[unky_gumbi]

I polish the edges on all my knives, ones I make, and ones I buy. I find that the polished edge is easier to maintain, a couple of swipes on a strop and its good to go. I think the last time I sharpened my D2 BM 710 was well over 2 months ago and it has been living in my pocket all that time.
Yes that initial tree topping sharpness is gone fairly quickly, but the usable sharpness stays much longer, simply because it was sharper to start.

Besides anyone that has looked at the knives I have made have all commented on how nice the polished, sharp edge looks. And those that have gotten one of my knives has commented on how nice it was to have a really sharp knife.

 

[Stacy E. Apelt - Bladesmith]

Rick is the authority on sharpening.
If a chef has a very expensive knife he just bought...and it is super sharp....he sends it to Rick to be properly sharpened before he uses it.

For most of us, a quick trip across a 220 grit belt and a pass each way on a paper wheel or felt buff will make a very sharp knife edge. However, the pros would consider that toothy edge a saw.

More important than the smoothness of the edge is the geometry of the blade and edge. Sharpen and polish an axe, and it will be sharp...but will still be an axe. The first part of sharpening is to match the edge thickness and angles to the job the blade will be doing.

 

[butcher_block]

Rick is the authority on sharpening.
If a chef has a very expensive knife he just bought...and it is super sharp....he sends it to Rick to be properly sharpened before he uses it.

For most of us, a quick trip across a 220 grit belt and a pass each way on a paper wheel or felt buff will make a very sharp knife edge. However, the pros would consider that toothy edge a saw.

More important than the smoothness of the edge is the geometry of the blade and edge. Sharpen and polish an axe, and it will be sharp...but will still be an axe. The first part of sharpening is to match the edge thickness and angles to the job the blade will be doing.

a razor is a fine edge but it is fragile. Nothing kills me more then a knife maker seeing one of my razors and asking if its sharp(then before i can tell them not to drag a finger across the edge sidways ) After they do that i have to put the razor under the table as they jsut destroyed the edge and its no longer shave ready (thats right jsut a light side load can take the edge right off)

i have also cut myself in the shop on a bar of steel that i was squaring up and wanted a nice crisp edge on (even 90 degree edge polished or toothy can cut you )

So just like the steel you use and the HT you pick for the tool you also neeed to make the edge geometry right and also pick the proper type of sharpening

 

[Rick Marchand]

Rick is the authority on sharpening.
If a chef has a very expensive knife he just bought...and it is super sharp....he sends it to Rick to be properly sharpened before he uses it.

Ha!.... Who would trust me to be an authority? Silly bean Funny you mention chef knives, though. I spent all day yesterday sharpening knives for a weekend event that a local culinary school is holding. (12 sets of 7 knives, total). Perhaps I came off too harsh? That wasn't my intention. I just spend A LOT of time sharpening because I love that aspect of blademaking. Some may embellish their finishes... others, engraving or filework. For me, it's the cutting edge and geometry. It's all just opinions in the end. There are sooo many variables in performance tests. I may be confident in my own experience but by no means, claim to be an expert.

For most of us, a quick trip across a 220 grit belt and a pass each way on a paper wheel or felt buff will make a very sharp knife edge. However, the pros would consider that toothy edge a saw.

I'm not too familiar with paper wheels.... but I would imagine a 220 with a paper wheel finish is pretty polished. I have used a 240 belt and 2 loaded leather belts to finish and the edge was pretty good. I bought one of those USB digital 400-1000x microscopes to run some tests. It really allows you to see the gradual degradation of an edge and how different geometries and finishes effect wear.... and that's not even getting into the metallurgy.

I used the toothy/saw analogy just for clarity, Stacy. It is not as literal as you may think I meant it. Sorry if I offended anyone. It is obvious that I prefer a polished edge... but I do not downplay the usefulnes of a toothy one. Like you said, apples and oranges.

More important than the smoothness of the edge is the geometry of the blade and edge. Sharpen and polish an axe, and it will be sharp...but will still be an axe. The first part of sharpening is to match the edge thickness and angles to the job the blade will be doing.

Totally agree.... the sharpness will get you in but everything after the edge will dictate how the blade performs.


Rick

 

[Kevin R. Cashen]

Initial edge condition is one thing but when that edge begins to wear this is actually quite a complex area of study. Some edges will go smooth and dull others will get more ragged as they wear, is this sharp? Not actually, but it does tear and saw more aggressively than a smooth edge.

Push cut versus draw cut- saws stink in a push cut but smooth chisels are a breeze, this is certainly Butches area of expertise and I am sure the point is not lost on him. The steel chosen and its proper heat treatment is critical to all of this, and not just the hardening and tempering. The hardness will determine how long the edge resists change but the prior thermal treatments and where you put the carbide will determine how that edge will wear.

Large unruly carbides will result in an edge that will either start out ragged, no matter how you try to sharpen it, or will quickly wear into a nasty micro saw that can still tear its way through things but fine cutting is lost. One can make these blade look like they stay sharp longer by carefully choosing targets that saw and tear more easily, paper, rope, some meats etc… The same is true of certain welded blade materials, cable, pure nickel and twists with instable weld zones, to name a few, or heavily segregated tool steels and blades cut from sheet perpendicular to the anisotropic rolling directing.

In fine kitchen cutlery, and certainly for Butch’s razors, all of the above quickly loose their luster because they cannot maintain an edge consistently within that golden 1 micron cutting zone. Edges like this need very fine and homogenous internal conditions, and are truly “sharp” with no degrees of raggedness until they finally fail to effectively perform their task.

 

[manassas dragon]

i wonder if the advantage(if any) of damascus is that the different steels give the blade
a toothiness that helps to keep the blade's ability to cut intact.

just a thought.

 

[Tiiiiiiiim]

i wonder if the advantage(if any) of damascus is that the different steels give the blade
a toothiness that helps to keep the blade's ability to cut intact.

just a thought.

The advantage of damascus is the look.

 

[me2]

blades cut from sheet perpendicular to the anisotropic rolling directing.

I've wondered about this before. Generally speaking, aren't the mechanical properies better in the rolling direction? If so, wouldn't that mean better properties if the blade is oriented so that the rolling direction is from spine to edge?

 

[jdm61]

My crazy English friend Ian, who a number of you probably met at Blade th last two years, sold me on the idea of a VERY sharp, highly polished edge, even on big knives. The lad came in 5th the first time he ever participated in the Blade Sports cutting comp finals using a knife made from O1. Nuff said.

 

[Stacy E. Apelt - Bladesmith]

Rick, I have to plead guilty for having a brain fart. I was remembering you as one who sharpens knives, but thinking of Dave Martel, who is the sharpening guru. The two of you fused into one in my mind.

 

[Rick Marchand]

Oh good, Stacy... I thought you may have been calling me out as an ass. I didn't want everybody finding out so soon.

I know of Dave Martel... I wish I could fuse minds with that guy when it comes to sharpening.

 

[hammerfall]

Initial edge condition is one thing but when that edge begins to wear this is actually quite a complex area of study. Some edges will go smooth and dull others will get more ragged as they wear, is this sharp? Not actually, but it does tear and saw more aggressively than a smooth edge.

Push cut versus draw cut- saws stink in a push cut but smooth chisels are a breeze, this is certainly Butches area of expertise and I am sure the point is not lost on him. The steel chosen and its proper heat treatment is critical to all of this, and not just the hardening and tempering. The hardness will determine how long the edge resists change but the prior thermal treatments and where you put the carbide will determine how that edge will wear.

Large unruly carbides will result in an edge that will either start out ragged, no matter how you try to sharpen it, or will quickly wear into a nasty micro saw that can still tear its way through things but fine cutting is lost. One can make these blade look like they stay sharp longer by carefully choosing targets that saw and tear more easily, paper, rope, some meats etc… The same is true of certain welded blade materials, cable, pure nickel and twists with instable weld zones, to name a few, or heavily segregated tool steels and blades cut from sheet perpendicular to the anisotropic rolling directing.

In fine kitchen cutlery, and certainly for Butch’s razors, all of the above quickly loose their luster because they cannot maintain an edge consistently within that golden 1 micron cutting zone. Edges like this need very fine and homogenous internal conditions, and are truly “sharp” with no degrees of raggedness until they finally fail to effectively perform their task.

:thumbup::thumbup::thumbup:

i believe that explain everything.