toothy or no toothy?

[NjMS]

I struggle with the range of "grits" the across the stones. Especially edge pro. I've heard that the 400 edge pro is equivalent to a Japanese 2000-3000, and that was from a reply with Ben. But that is contradictory to all the charts online. I'm after a good 25-40micron stone to trial more course edge finishes now and it's damn confusing looking around.

Sent from my D6503 using Tapatalk

 

[dantzk8]

The term grit seems to have no standard, it's all over the place.
For instance, 400 can range from 22 to 45 micron according to this Grand Unified Grit Chart, a 100% size range difference. Looking in the 22 to 45 micron range of the chart, you can find designations from 240 to 800.

I know this chart, very well made and useful when you want to mix different kinds of stone, diamond plates with hard ceramic or soft ceramic for instance.

What i meant is that there is a direct influence of the sharpening angle on the toothyness you get. If you sharpen a staight razor at 7 degrees, a wood carving knife at 20, a kitchen knife at 30, a camp knife at 40, all made of the same steel, with the same stone whatever the grit, the toothyness of those different edges will vary drastically.

You would notice as well that different stones behave very differently. A diamond plate provides deeper scratches than a hard ceramic stone which itself is more agressive than a soft ceramic.

The toothynes you want to get has not for only factor the stone grit. Edge angle and stone technology have to be taken in consideration.

dantzk.

 

[BellaBlades]

I have decided with refined steels like s35v or CPM 154 I use the dark rods on my sm and the dark blackm rouge on my strop. I feel if I go to the fine stones and the chromium oxide it just dulls quicker. The slightly coarser edge keeps stropping back up far easier.

 

[HeavyHanded]

My personal belief is that in the range of 600-800 ANSI is the sweet spot for most steels and geometries if used for a variety of tasks. I usually go a bit higher than that as I find it much easier to touch up a finer edge and do so with less steel loss per - the somewhat reduced longevity made up for by other factors and still have strong performance initially and for long enough to be plenty functional - YMMV based on the abrasives at hand and the type of work being performed.


My working theory is and has been for some time, that pressure is the number one killer of edge sharpness, all other things being equal (abrasive content of the target material). So whatever means will reliably part a given material with the least force or friction will also last longer than other strategies. Since not all materials are put together the same, one edge finish will not perform the best across the range, either initially or as the edge dulls.


A chisel sharpened up to 280 grit might work well enough for rough work, but it will require more effort to use and this will increase rapidly as it dulls. The same chisel sharpened up to +2000 ANSI will require less force and last a lot longer in use, as well as making much cleaner cuts. I have found this to carry through with many tool types. My hatchets, machetes, axes, Chef knives, chisels, plane irons etc are all taken to a bright polish and stay sharp longer for it, in some cases dramatically so.


For EDU the rougher finish outlasts the finer one in most cases by a comfortable margin in my experience - the presence of high carbide content or larger carbides will amplify this effect.


In some of my testing I found that edge finish was also related not just to longevity, but also to failure mode for a given material - a rougher edge might draw cut longer than a finer edge but also require a lot more force on a pressure cut, the amount of force increasing rapidly as the edge dulls. A finer edge might fail a draw cut test with many fewer cycles at a given load, but still perform very well on a pressure cut - in some instances outperforming the rougher edge freshly sharpened.

If possible to tailor the edge to the task, is a good idea to do so.


http://www.bladeforums.com/forums/showthread.php/1368637-BCMWn690

 

[Spey]

Any indication of a grit in regard of the polished or toothy result should to be mentionned with the sharpening angle.

More acute the edge angle deeper the serrations.

dantzk.

Absolutely ! [emoji106] (minimally ...)

I would also go a step further in that ...
1) Grit
2) Angle at cutting edge (lower = deeper)
3) Steel Type (relative carbine structure)
4) Stone or Plate (diamond vs ..., diamonds can cut deeper = more aggressive serrations in cutting edge).

should all be minimally mentioned when discussing cutting performance comparatively as relates to final grit selection.

Regards,

 

[Spey]

I saw lots of folks recommend a toothy yet sharp edge and I understand it is a better choice for cutting things like cardboard boxes. For tasks like peeling apples which require push cutting, is it true that a highly polished (i.e., less toothy) edge should be preferred?

You should really try both for yourself. It would go a long way in helping you to understand different peoples opinions on the subject. The differences are significant when experienced first-hand, once you feel how they vary on different cutting mediums.

Regards,

 

[kane22]

In general do you guys think high carbon steel would do better with a toothy edge, and the high end cpm type stainless with more of a polished edge? I think the carbides in high carbon steel would bigger, and may be better suited for a toothy edge??? Or maybe it doesn't make any difference.

 

[linuxology]

Typically 600-1000 grit is enough, but I like to go with polish edges from time to time.

 

[MichaelMyers]

Diamond stones does produce a toothy yet sharp edge at least when new. 600 lansky diamond is almost as toothy as 280 lansky AO. Hardness of the steel matters too. A harder steel will finish up less toothy on the same stone due to the shallower depth of scratch pattern.

 

[Chris "Anagarika"]

In general do you guys think high carbon steel would do better with a toothy edge, and the high end cpm type stainless with more of a polished edge? I think the carbides in high carbon steel would bigger, and may be better suited for a toothy edge??? Or maybe it doesn't make any difference.

Generally, high carbon steel will work better with polished edge, where high end stainless (i.e. more carbides, such as S30V) should work better with toothier edge. It still depends on the heat treat as some heat treat doesn't result in fine structure.
For example, the recent Military 52100 discussion, people found that 52100 likes polished edge better. I consider 52100 as high carbon steel (some might have different opinion). High carbide stainless (S30V) has repeatedly reported to last longer with toothier edge. I have observed the same for 52100 (custom, not Spyderco), but haven't tried S30V. Personally, I like polished edge because of my use case (light general cutting and more often shaving).

Spey is right, one should try varying the finish to suit the most use case one has. It's going to give better result that way.

 

[Sticky]

My knives: Toothy My straight razors: no toothy

 

[jpm2]

I know this chart, very well made and useful when you want to mix different kinds of stone, diamond plates with hard ceramic or soft ceramic for instance.

What i meant is that there is a direct influence of the sharpening angle on the toothyness you get. If you sharpen a staight razor at 7 degrees, a wood carving knife at 20, a kitchen knife at 30, a camp knife at 40, all made of the same steel, with the same stone whatever the grit, the toothyness of those different edges will vary drastically.

You would notice as well that different stones behave very differently. A diamond plate provides deeper scratches than a hard ceramic stone which itself is more agressive than a soft ceramic.

The toothynes you want to get has not for only factor the stone grit. Edge angle and stone technology have to be taken in consideration.

Yes, I agree completely with what you said, just pointing out that grit means almost nothing, except as a reference between stones from the same manufacturer.

One other point... the steel being sharpened makes a difference. Given consistent pressure, even a diamond stone will cut to different depths with different alloyed (or not alloyed) steels. EDIT: I see member Spey already mentioned this.

3) Steel Type (relative carbine structure)

There's a lot of variables.

 

[dantzk8]

... the steel being sharpened makes a difference. Given consistent pressure, even a diamond stone will cut to different depths with different alloyed (or not alloyed) steels. EDIT: I see member Spey already mentioned this.

The problem, for me, with highly alloyed steels is that they behave coherently when sharpened with a coarse stone and randomly with fine stones particularly with diamonds plates. With a coarse stone you get as expected a toothy edge with an agressive slicing ability, with a fine stone you can get a very keen edge or a dulled one and sometimes both results on different parts of the edge. It certainly has something to see with the distribution and sizes of the different carbides. I'm not a metallurgist, i can't go further, i'm just talking from my limited experience. I would bet that people who prefer toothy edges are the ones who use highly alloyed steels. Those who prefer carbon steels and low alloyed steels don't generally pay so much attention to the final completion if they don't plan a specific task.

dantzk.

 

[Ben Dover]

It depends on your personal preference.

I prefer at lest 10K and then stropping down to .25 micron. No toothiness at all.

Many prefer a coarser edge.

 

[mendel314]

It's entirely dependent on two factors: angle and steel type. High carbide volume steels and steels with large carbides (like d2) see no benefit from polished edges. Carbides will pull out of matrix at acute angles and the edge will become toothy quickly. A simple steel, like 1095, will polish nicely, since there aren't large carbides. Any edge will perform best (for slicing/cutting) at the most acute angle at which it is stable, and the optimal level of polish is determined by the mode of failure.

Yes, I agree completely with what you said, just pointing out that grit means almost nothing, except as a reference between stones from the same manufacturer.

One other point... the steel being sharpened makes a difference. Given consistent pressure, even a diamond stone will cut to different depths with different alloyed (or not alloyed) steels. EDIT: I see member Spey already mentioned this.

There's a lot of variables.

 

[Jason B.]

It's entirely dependent on two factors: angle and steel type. High carbide volume steels and steels with large carbides (like d2) see no benefit from polished edges. Carbides will pull out of matrix at acute angles and the edge will become toothy quickly. A simple steel, like 1095, will polish nicely, since there aren't large carbides. Any edge will perform best (for slicing/cutting) at the most acute angle at which it is stable, and the optimal level of polish is determined by the mode of failure.

Almost,

D2 is a bad example because D2 works very well with a high polish, that's actually one of its main features. I've used D2 with a belt sharpened edge at 120 grit all the way up to a hand sharpened edge at 16,000 grit, both performed very well and dare I say without much difference in edge retention.

Edge angle only comes into the equation when speaking of edge retention. At which time you must also factor in steel hardness and behind the bevel thickness.

Carbides do not pull out of the matrix, this myth is just that.

 

[mendel314]

Almost,

D2 is a bad example because D2 works very well with a high polish, that's actually one of its main features. I've used D2 with a belt sharpened edge at 120 grit all the way up to a hand sharpened edge at 16,000 grit, both performed very well and dare I say without much difference in edge retention.

Edge angle only comes into the equation when speaking of edge retention. At which time you must also factor in steel hardness and behind the bevel thickness.

Carbides do not pull out of the matrix, this myth is just that.

This is incorrect. Large carbides are brittle, and will fracture. This leaves loose pieces which fall out. With small carbides, this issue is largely mitigated. The two most common abrasive tribologies are ploughing the matrix and brittle failure of carbides. You're correct the the carbides don't exactly "pull out," but the effect is identical.

Do you mean cpm d2 or cast d2? They are worlds apart in this regard. Most pm steels have fine carbides, but cast d2 has some of the largest of any cutlery steel. This is its biggest benefit - it produces very toothy edges because large exposed carbides wear very slowly and cut extremely well (like tiny serrations)

Any steel can be polished by abrasives sufficiently harder than its carbides, but the larger carbides breaking will remain a failure mode, and large pieces will fall out. Think of it like teeth. If one shatters, parts of it will fall out until the whole is gone, and the effect is the same as having a tooth pulled - a hole in the matrix (gums).

Excessive polishing of large carbide steels has the effect of exposing them, meaning they are less well supported and easier to fracture from more directions. To continue the dental analogy, imagine a molar compared to a front tooth

 

[HeavyHanded]

I dunno about that...

The effect might be overblown in many cases, but ekretz took a series of micrographs that would seem to support carbide displacement very convincingly, at least at the abrasive level. I've taken micrographs that appear to show pitting from carbide loss, but they are not as clear as the ones eKretz captured.


http://www.bladeforums.com/forums/s...stant-steels-(S30V-S90V-CTS204P-etc)/page2#31


Whether this becomes an issue in actual usage, say when the edge is exposed to lateral pressure etc is likely dependent on a host of factors like RC and edge geometry.


Was lucky enough to get one of Bluncut's developmental D2 pieces, run to 61-62 RC. It takes and holds a fine edge very well. My BK24 at the same edge angle and at lower RC does not hold the fine edge for any length of time before defaulting back to a medium toothy cutting edge - where it can run for a long time without further change of character. YMMV

 

[Jason B.]

This is incorrect. Large carbides are brittle, and will fracture. This leaves loose pieces which fall out. With small carbides, this issue is largely mitigated. The two most common abrasive tribologies are ploughing the matrix and brittle failure of carbides. You're correct the the carbides don't exactly "pull out," but the effect is identical.

Do you mean cpm d2 or cast d2? They are worlds apart in this regard. Most pm steels have fine carbides, but cast d2 has some of the largest of any cutlery steel. This is its biggest benefit - it produces very toothy edges because large exposed carbides wear very slowly and cut extremely well (like tiny serrations)

Any steel can be polished by abrasives sufficiently harder than its carbides, but the larger carbides breaking will remain a failure mode, and large pieces will fall out. Think of it like teeth. If one shatters, parts of it will fall out until the whole is gone, and the effect is the same as having a tooth pulled - a hole in the matrix (gums).

Excessive polishing of large carbide steels has the effect of exposing them, meaning they are less well supported and easier to fracture from more directions. To continue the dental analogy, imagine a molar compared to a front tooth

If you say so...

 

[Chris "Anagarika"]

I also have BCMW D2 63 HRC, development stage, not yet CWF if I recall correctly. Hold the high polished edge pretty well, at DMT EE.
I like my knives like Ben, high polished edge. My usage is light though.

So YMMV, test & learn.