"Dragging" the Burr Off - Is This a Popular Technique?

A toothy edge is made up of small serrations, that because of their geometry, don't have a lot of longevity. This is especially true if the edge is used to cut more resistant materials. Great for cutting cloth, not so good at slicing leather. A more refined edge last longer because of it's geometry. A smoother surface without protrusions.

"Who told you that"? It came about after making a thousand knives and sharpening many more. Experience is the best teacher.


Who told you they do last a long time? Not me :) :eek:



Fred
 
Actually, CATRA testing is what really opened my eyes. It can tell you more in one run than years of experience could ever.

The teeth on the edge create more surface area at the apex taking longer to wear down than edges of higher refinement. Controlled testing proves this over and over.
 
I've seen that but I don't put much stock in it. The supporting structure of a toothy edge is more fragile than a refined edge and doesn't hold up. I think this is even more noticeable when the blade is thin and the edge is acute.
There are far to many variables in testing something like a toothy edge and there lies the rub. One man's toothy is another mans refined.

I will be investing in a high resolution USB microscope later this year. I believe I have something worth photographing these days and nothing like a picture to make a point.
I would like to have an electron microscope, but alas they are out of my budget.

Regards, Fred
 
My own testing showed exactly what I'd come to believe informally.

A toothy edge lasts a lot longer when the primary cutting mechanism is a draw, a fine edge lasts longer when the primary mechanism is pressure on a static edge.

For a variety of chores, something in between is best. There is no blanket "best edge" strategy, only compromises based on what the tool is expected to do.

http://www.bladeforums.com/forums/showthread.php/1368637-BCMWn690?highlight=BCMWn690
 
Fred,

In my own informal testing, I found that a 4 micron finish (Norax belt) compared to a 100 micron finish (Norax belt) had dramatically different edge holding. What was my testing? Opening cardboard boxes, sealed with tape at my job. I found a 2x to 3x increase in the ability to keep a "box cutting edge" when I switched to the more coarse edge.

I know you are a smart guy, a knife enthusiast, and a skilled knife maker. But I wonder if you've done any real world type testing, that resembles mine in any way. Meaning, cutting something that's somewhat the same, using the exact same blade, and different finishes. Rope cutting, slicing cardboard, etc, to me are interesting, but they seem flawed. Because no one does that with a knife blade. No one cuts rope into 1/2 sections hundreds of times.

I did my test just as part of doing my job. I wanted my edge to last longer between sharpening sessions. Moving to a more coarse edge finish did this and it was rather obvious. But that's just my VERY INFORMAL results. Very un-scientific. But still valid I think.

Thanks for reading.

Brian.
 
bgentry said:
Fred,

In my own informal testing, I found that a 4 micron finish (Norax belt) compared to a 100 micron finish (Norax belt) had dramatically different edge holding. What was my testing? Opening cardboard boxes, sealed with tape at my job. I found a 2x to 3x increase in the ability to keep a "box cutting edge" when I switched to the more coarse edge.

I know you are a smart guy, a knife enthusiast, and a skilled knife maker. But I wonder if you've done any real world type testing, that resembles mine in any way. Meaning, cutting something that's somewhat the same, using the exact same blade, and different finishes. Rope cutting, slicing cardboard, etc, to me are interesting, but they seem flawed. Because no one does that with a knife blade. No one cuts rope into 1/2 sections hundreds of times.

I did my test just as part of doing my job. I wanted my edge to last longer between sharpening sessions. Moving to a more coarse edge finish did this and it was rather obvious. But that's just my VERY INFORMAL results. Very un-scientific. But still valid I think.

Thanks for reading.
Brian.
Click to expand...

What is a toothy edge? There's no standard I don't think. To me a toothy edge is one that is not refined after the burr is removed by breaking or snapping it off. When I work that edge to refine it then its no longer toothy. I have not found that edge to stand up; the apex is what remains after the burr is removed and that edge is extremely chippy.
Is there some standard for toothy? That would give this some clarity. Like many knife blade terms, there is not much standardization.

Fred
 
I know in my profession that a less refined edge works better cutting certain proteins and vegetables, and as a hobbyist that some steels perform better at a lower grit than others. We can start getting wrapped up in the semantics of what defines toothy and go round and round but a more refined edge is not always better.

Russ
 
Fred.Rowe said:
What is a toothy edge? There's no standard I don't think.
Click to expand...

As I said in my post, I tested with a 100 micron belt to finish my edge. That was my coarse (or toothy) edge finish. My finer finished edge was doine with a 4 micron belt.

To me a toothy edge is one that is not refined after the burr is removed by breaking or snapping it off. When I work that edge to refine it then its no longer toothy. I have not found that edge to stand up; the apex is what remains after the burr is removed and that edge is extremely chippy.
Click to expand...

I would not have used that definition myself. From what I understand, a "toothy edge" is one that is finished with a more coarse abrasive. How coarse is the end of toothy and the beginning of "fine" ? Who knows. I'd say the transition zone for me personally is around 600 to 800 grit. That's where toothy becomes refined. Like you said, the term itself isn't very specific. But I put numbers to my test so we can talk about specifics.

I can understand, with your definition, that this type of "burr ripped off" edge would have all kinds of weak pieces and parts stuck to the apex that wouldn't hold up to much use at all. Again, I don't think most people here are using that definition when they use the term "toothy edge".

Brian.
 
mycough said:
I know in my profession that a less refined edge works better cutting certain proteins and vegetables, and as a hobbyist that some steels perform better at a lower grit than others. We can start getting wrapped up in the semantics of what defines toothy and go round and round but a more refined edge is not always better.

Russ
Click to expand...

I agree with you there, a more refined edge is not always ideal. Since I make knives I usually go for changing the geometry of the edge, thicker, thinner, more acute, less acute angle at the edge.
It's like discussing a "working edge" which can take up volumes with little clear outcome.

What do you consider a "toothy" edge Russ?

Brian, My 600 or 800 grit finished edge, I don't see as toothy at all if I've taken the edge to zero on the belt. I should have thought ahead and realized I was opening up a can of worms. I shouldn't have made exacting comments about something so subjective as this topic. My apology.


Regards, Fred
 
Last edited:
Knives can shave hair and cleanly cut paper at 300grit

Because the apex is "refined" clean and without a burr.

It's just not as sharp as an edge with a higher Finish like 10,000grit but that polished edge won't last.

It all about finding that balance with grit selection to find the right amount of tooth (longevity)and polish (precision). For the right task and steel.


Polished toothy FTW haha
 
bgentry said:
As I said in my post, I tested with a 100 micron belt to finish my edge. That was my coarse (or toothy) edge finish. My finer finished edge was doine with a 4 micron belt.



I would not have used that definition myself. From what I understand, a "toothy edge" is one that is finished with a more coarse abrasive. How coarse is the end of toothy and the beginning of "fine" ? Who knows. I'd say the transition zone for me personally is around 600 to 800 grit. That's where toothy becomes refined. Like you said, the term itself isn't very specific. But I put numbers to my test so we can talk about specifics.

I can understand, with your definition, that this type of "burr ripped off" edge would have all kinds of weak pieces and parts stuck to the apex that wouldn't hold up to much use at all. Again, I don't think most people here are using that definition when they use the term "toothy edge".

Brian.
Click to expand...

That's how I'm viewing it as well. I refer to such edges as 'tattered', as opposed to toothy. A 'tattered' edge, to me, would be what's left after the burr tears off, and more so with even heavier, thicker burrs being ripped away. But, with the right steels coarsely honed to the point where remnants of very, very thin burrs just break away pretty much on their own, the coarse 'teeth' left by the hone itself can be very durable, as separate and distinguished from the 'tattered' remnants of whatever burr might've been there.

There are some steels that won't hold coarse teeth very well, though. I've noticed it with some knives in low-alloy stainless, like 420HC, which tend to lose their teeth to abrasive wear very, very quickly. A few swipes on a green-compounded strop of leather have been able to strip them away from edges finished at ~320 or so, leaving the edge immediately feeling, to the fingertips, more like an 600/800-grit edge.


David
 
Chris "Anagarika";16523099 said:
DBH,

Polished toothy .... You mean like Jason's recommendation DMT C and strop on 1 micron diamond paste ?
Click to expand...

Chris, that was one instance I was alluding to. M390 many be my favorite folder steel and works like a charm sharpened this way.
The edge lasts too... one of my elmax folders from Alan Davis also gets this finish and cuts forever, part of that is his grind and HT.
Just got a bluntcut metalworks in cts xhp, if it ever dulls I am gonna try this strategy on it.

Russ
 
mycough said:
Chris, that was one instance I was alluding to. M390 many be my favorite folder steel and works like a charm sharpened this way.
The edge lasts too... one of my elmax folders from Alan Davis also gets this finish and cuts forever, part of that is his grind and HT.
Just got a bluntcut metalworks in cts xhp, if it ever dulls I am gonna try this strategy on it.

Russ
Click to expand...

Russ,

Thanks. Please do a review on that BCMW.
I think we're OT now. Perhaps the toothy vs polished discussion needs to continue in that old thread?
 
Chris "Anagarika";16523099 said:
DBH,

Polished toothy .... You mean like Jason's recommendation DMT C and strop on 1 micron diamond paste ?
Click to expand...

Yes, I like the 400 chosera and the 1 micron

You could also do a 1k king with stroping on a 6k king stone.

The possibilities are limitless

Especially when you factor in different steels
 
HeavyHanded said:
My own testing showed exactly what I'd come to believe informally.

A toothy edge lasts a lot longer when the primary cutting mechanism is a draw, a fine edge lasts longer when the primary mechanism is pressure on a static edge.

For a variety of chores, something in between is best. There is no blanket "best edge" strategy, only compromises based on what the tool is expected to do.

http://www.bladeforums.com/forums/showthread.php/1368637-BCMWn690?highlight=BCMWn690
Click to expand...

Can you explain why you believe this is the case?

Thanks, Fred
 
Fred.Rowe said:
Can you explain why you believe this is the case?

Thanks, Fred
Click to expand...

I think of a serrated edge as an edge with very large teeth, and by the same token, a "toothy edge" is just an edge with very fine serrations. I have seen how a serrated edge will still draw cut very effectively, after being hammered repeatedly, edge-first, into a brick, or at least rubbed across a brick. I saw a video of it. A plain edge will not do that. So I would tend to believe it, based on that. Not scientific, I know, but that has been my line of thinking.
 
Last edited:
You must log in or register to reply here.
Back
Top