Why so sharp?

[somber]

Close the thread? Why? There's no flaming going on, knifenut1012 had a misunderstanding and thought I was insulting him. But now it's just getting weird with all these compliments flying from everyone, so maybe that might be for the best, actually. But I don't see what's getting out of hand.

Carry on with the discussion: Why so sharp?

 

[neeman]

So im fairly new to the forums here but see that a lot of people are working to get their knives crazy sharp and I ask why. The knives I have are used everyday and are usually beaten up by daily tasks. I have a DMT c/f duofold that gets them sharp in a short amount of time. Ive never have a knife that could pop the hairs off my arms but they can definately perform whatever task that I throw at them. So I'm wondering if its worth it to go that extra distance and get them crazy sharp or is it just a time if they are constantly used and abused?

I have learnt a vast amout of information from folks here about 'scary' sharp.
Perhaps my knives will never be scary sharp, but the quality of my knife sharpening has improved dramatically.
For the same amount of effort I have significantly sharper knives

When the whole hoopla about knives is over, we are left with a blade to cut with.
The better it cuts and the less frequently I need to restore it to a good edge means it is a better tool
So the better the edge, the better the function of the knife

The rest is personal choice, knowledge, and investment of time

 

[Gadgetaholic]

I find that once I have the edge that I am happy with I can keep it that way with a couple of minutes (maybe 5) with a strop on a regular basis. Unless I work the knife hard enough to really blunt or damage the edge it never takes much work to get it back to 'scary sharp'.

 

[HeavyHanded]

What changed my mind about highly polished razor like edges was when I tried to cut some 1/2" manila rope. The hairs on my arm would jump off by them selves at just the appearance of the knife , but it just slid off the rope. I made a few passes on my crock stick and it went through the rope like it wasn't there. My only explanation is that the edge need some "tooth" to bite into the rope.

Your results may very.

I used to do a three-part test for cutting performance on my knives after honing. First I'd cut a few lengths of 3/8 sisal, cut a thin piece off of a block of soft foam, and then push-cut some paper. I ran into the same thing, it appeared to be a contradiction - the "less sharp" edge performed better on the first two tests, not so good on the push test. I started pushing the envelope in both directions (fine and coarse) and expanding the test media. At the fine end I went as far as a barber's hone and could dry-shave (not so comfortably) the stubble off my cheek. At the coarse end I went as far as a 60grit tile finishing stone. The more coarse the better it performed on the rope and the foam (with a draw cut). Hard use at work favored the coarse edge as well, by a substantial margin. At the fine end, it performed much better for push cutting. The ironic thing is the coarse edge actually cuts with less pressure than the fine edge as long as some draw is used. Came to the conclusion that the fine edge was only worth the effort if I wasn't using the knife too much, or it was for shaving, carving, or leather work. The coarse edge also seemed to perform better for "tactical" use (it blasted through multiple layers of denim backed with high-density foam) and there's no contest on heavy canvas materials like seatbelts etc. I also find a coarse edge with a drawing action cuts more predictably, lessening the chance of my knife suddenly passing the resistance threshold of a given material and cutting loose. To each his own, unless I have a specific reason to take it to a face-shaving edge I've got better things to do, like go online and talk about it...

 

[lwt210]

Carry on with the discussion: Why so sharp?

I like to hear my coworkers and friends whine about cutting themselves and how I got it "too sharp".

But I do agree that I have edges that will push cut news print, shave hair where it jumps from your arms and all that jazz that won't cut some items as well as a toothy edge.

I usually leave a toothy edge on my edc stockman for those types of cutting tasks.

I still like to strop a blade or two to gleaming goodness. It relaxes me. Same as tying paracord knots. Makes time pass.

 

[Any Cal.]

To each his own, unless I have a specific reason to take it to a face-shaving edge I've got better things to do, like go online and talk about it...

Very nice. 'Cause when it is all said and done, what good is it if we can't go talk about it with a bunch of other nuts?

 

[hardheart]

i use 30* per side, alot. in fact, 25* per side is as acute as i go.

ETA - unless the measurements on the Lansky are referring to inclusive.

They are not inclusive, you can just look at the guide rod in the clamp and see that. I just checked my old one against a laser goniometer & a benchstone angle guide I made to confirm, though that isn't necessary. No one should have trouble visualizing a 45 degree angle. If the angles on the Lansky were inclusive, the angle between the clamp & guide rod in the 25 degree slot would be at 1/4 the angle of a 45. If the angles are per side, then it would look like it was halfway to a 45. Now, just have a look. For the Lansky angles to be inclusive, your knife would have to be somewhere around 6 inches wide to put the sharpening stone at the right angle.

But the angles aren't too accurate anyway, because it depends on the knife thickness, width, and placement in the clamp.

 

[scs.knives]

it's fun, and i'm addicted to it

 

[nozh2002]

I used to do a three-part test for cutting performance on my knives after honing. First I'd cut a few lengths of 3/8 sisal, cut a thin piece off of a block of soft foam, and then push-cut some paper. I ran into the same thing, it appeared to be a contradiction - the "less sharp" edge performed better on the first two tests, not so good on the push test. I started pushing the envelope in both directions (fine and coarse) and expanding the test media. At the fine end I went as far as a barber's hone and could dry-shave (not so comfortably) the stubble off my cheek. At the coarse end I went as far as a 60grit tile finishing stone. The more coarse the better it performed on the rope and the foam (with a draw cut). Hard use at work favored the coarse edge as well, by a substantial margin. At the fine end, it performed much better for push cutting. The ironic thing is the coarse edge actually cuts with less pressure than the fine edge as long as some draw is used. Came to the conclusion that the fine edge was only worth the effort if I wasn't using the knife too much, or it was for shaving, carving, or leather work. The coarse edge also seemed to perform better for "tactical" use (it blasted through multiple layers of denim backed with high-density foam) and there's no contest on heavy canvas materials like seatbelts etc. I also find a coarse edge with a drawing action cuts more predictably, lessening the chance of my knife suddenly passing the resistance threshold of a given material and cutting loose. To each his own, unless I have a specific reason to take it to a face-shaving edge I've got better things to do, like go online and talk about it...

This is Really interesting. Can you provide more details (may be in separate thread)? With pictures and numbers if possible? Video will be even better.

Do you polish you coarse edge? I recently tried to go to Grean Rouge right after 120 grip, I cuts, but I can not say yet is it good or not - for sure it bit different. I remember one knifemaker show this, but to my shame I forgot his name.

Thanks, Vassili.

 

[HeavyHanded]

This is Really interesting. Can you provide more details (may be in separate thread)? With pictures and numbers if possible? Video will be even better.

Do you polish you coarse edge? I recently tried to go to Grean Rouge right after 120 grip, I cuts, but I can not say yet is it good or not - for sure it bit different. I remember one knifemaker show this, but to my shame I forgot his name.

Thanks, Vassili.

Nope, I never bothered to polish the coarse edge except for a very few tests that all seemed to indicate it was detrimental. There's no way I can take the time to redo these experiments - the wife would bundle up all my sharpening stones and cram 'em up my backside if I started to disappear every night for an hour or two like I used to.

Funny thing about how I came to favor the coarser edge - I worked my way up to the barber's hone and then started making a few passes on a 300 grit stone to "put some teeth on it". Realized it was a lot easier to just work with the 300 (and rougher) stones directly. IMHO 200-300 grit is just scraping the surface (no pun intended) of what I define as a "coarse" edge. Anything higher is "medium" and everything over 1200 grit is "fine". Your 120 grit should produce good results without polishing. Just do as you normally would with a finer git, namely once you've established a burr on both sides apply a little less pressure and keep going till you're barely using the weight of the blade and the burr is completely gone. Contrary to what a lot of folks assert, it probably won't feel terribly sharp but it will cut very well with a draw. The key (as with any edge treatment) is to eliminate the burr as best you can. Again, IMHO at the very low-grit end of things, using a strop will not improve the performance of the edge and I believe it makes it marginally less effective, you're essentially using a higher grit to clean up the edge, but in this case you want the edge to have as much texture as possible - you're going backwards. I also find it's not really useful for removing the burr beyond what can be done with the same stone you used to grind the edge. I can't speak for the paper wheel treatment - I don't have one to test it out for myself. A last thought, people seem to have no qualms about purchasing different honing materials and learning different techniques for a highly polished edge if they don't like what they have, but very few take the time to seek out the better grinding media or fine-tuning their practices for applying a coarse edge. If you don't think your 120 grit stone is doing what you need it to, try a different one, esp if it's a natural stone - they're not all equal. To me, "sharp" is simply both planes of the edge coming together as cleanly as the grinding/polishing media being used will allow. Beyond that the edge treatment needs to be tailored to the task at hand. For me a pocket utility/tactical knife performs best with an abrasive edge, my camping hatchet on the other hand, is honed to a hair-popping edge and it works great for what I need it to do.

HH

 

[zyhano]

Nope, I never bothered to polish the coarse edge except for a very few tests that all seemed to indicate it was detrimental. There's no way I can take the time to redo these experiments - the wife would bundle up all my sharpening stones and cram 'em up my backside if I started to disappear every night for an hour or two like I used to.

Funny thing about how I came to favor the coarser edge - I worked my way up to the barber's hone and then started making a few passes on a 300 grit stone to "put some teeth on it". Realized it was a lot easier to just work with the 300 (and rougher) stones directly. IMHO 200-300 grit is just scraping the surface (no pun intended) of what I define as a "coarse" edge. Anything higher is "medium" and everything over 1200 grit is "fine". Your 120 grit should produce good results without polishing. Just do as you normally would with a finer git, namely once you've established a burr on both sides apply a little less pressure and keep going till you're barely using the weight of the blade and the burr is completely gone. Contrary to what a lot of folks assert, it probably won't feel terribly sharp but it will cut very well with a draw. The key (as with any edge treatment) is to eliminate the burr as best you can. Again, IMHO at the very low-grit end of things, using a strop will not improve the performance of the edge and I believe it makes it marginally less effective, you're essentially using a higher grit to clean up the edge, but in this case you want the edge to have as much texture as possible - you're going backwards. I also find it's not really useful for removing the burr beyond what can be done with the same stone you used to grind the edge. I can't speak for the paper wheel treatment - I don't have one to test it out for myself. A last thought, people seem to have no qualms about purchasing different honing materials and learning different techniques for a highly polished edge if they don't like what they have, but very few take the time to seek out the better grinding media or fine-tuning their practices for applying a coarse edge. If you don't think your 120 grit stone is doing what you need it to, try a different one, esp if it's a natural stone - they're not all equal. To me, "sharp" is simply both planes of the edge coming together as cleanly as the grinding/polishing media being used will allow. Beyond that the edge treatment needs to be tailored to the task at hand. For me a pocket utility/tactical knife performs best with an abrasive edge, my camping hatchet on the other hand, is honed to a hair-popping edge and it works great for what I need it to do.

HH

that's a very well made point. I invest in the higher grits, but not in the lower grits. Just recently I got the XXC dmt benchstone and was very surprised with what I could do with that. It gives a very clean and tight scratch pattern.
Now, I probably won't go looking for other coarse stones, but that's exactly your point.
There is a lot of thought and energy going into the fine edges, but not so much in the not-so-refined edges.

And for the touch-em-up-quick guys that's probably where their major gain is.

 

[hardheart]

it's hard to apply a definition/micron or grit rating to coarse, medium, fine. Norton calls their Crystolon fine at 240 grit & India at 280. The coarsest stone a razor is likely to see these days is about 1000 grit. Similarly, some foodies say they go to 800-1000 grit when they need to repair an edge, not finish a sharp one.

When I started, I used one of those old SiC combo stones, then I got myself a Lansky and never went past the medium (280) stone. Edges worked fine for me, shaved arm hair, and I got there quickly. Now I have some 0.3 micron lapping film, 0.25 micron diamond powder, and buffing wheels loaded with compound, along with various natural and synthetic 'finishing' stones. I still like to get a carbon steel edge to shaving sharp with nothing but a file to keep perspective. I got myself a small smooth file to get a 'finer' edge than one a single cut bastard will create to make edges cleaner

 

[nozh2002]

Nope, I never bothered to polish the coarse edge except for a very few tests that all seemed to indicate it was detrimental. There's no way I can take the time to redo these experiments - the wife would bundle up all my sharpening stones and cram 'em up my backside if I started to disappear every night for an hour or two like I used to.

Funny thing about how I came to favor the coarser edge - I worked my way up to the barber's hone and then started making a few passes on a 300 grit stone to "put some teeth on it". Realized it was a lot easier to just work with the 300 (and rougher) stones directly. IMHO 200-300 grit is just scraping the surface (no pun intended) of what I define as a "coarse" edge. Anything higher is "medium" and everything over 1200 grit is "fine". Your 120 grit should produce good results without polishing. Just do as you normally would with a finer git, namely once you've established a burr on both sides apply a little less pressure and keep going till you're barely using the weight of the blade and the burr is completely gone. Contrary to what a lot of folks assert, it probably won't feel terribly sharp but it will cut very well with a draw. The key (as with any edge treatment) is to eliminate the burr as best you can. Again, IMHO at the very low-grit end of things, using a strop will not improve the performance of the edge and I believe it makes it marginally less effective, you're essentially using a higher grit to clean up the edge, but in this case you want the edge to have as much texture as possible - you're going backwards. I also find it's not really useful for removing the burr beyond what can be done with the same stone you used to grind the edge. I can't speak for the paper wheel treatment - I don't have one to test it out for myself. A last thought, people seem to have no qualms about purchasing different honing materials and learning different techniques for a highly polished edge if they don't like what they have, but very few take the time to seek out the better grinding media or fine-tuning their practices for applying a coarse edge. If you don't think your 120 grit stone is doing what you need it to, try a different one, esp if it's a natural stone - they're not all equal. To me, "sharp" is simply both planes of the edge coming together as cleanly as the grinding/polishing media being used will allow. Beyond that the edge treatment needs to be tailored to the task at hand. For me a pocket utility/tactical knife performs best with an abrasive edge, my camping hatchet on the other hand, is honed to a hair-popping edge and it works great for what I need it to do.

HH

I uses green rouge polish just to get rid of burr, just to clean toothed edge from whatever part of metals it has - at least this is my theory.

I do my regular sharpening - whittling hair is what I am looking for at the end.

But I do not know what to looking for in case of this coarse edge. What is your criteria, when you know you are done?

Thanks, Vassili.

 

[HeavyHanded]

I uses green rouge polish just to get rid of burr, just to clean toothed edge from whatever part of metals it has - at least this is my theory.

I do my regular sharpening - whittling hair is what I am looking for at the end.

But I do not know what to looking for in case of this coarse edge. What is your criteria, when you know you are done?

Thanks, Vassili.

Yeah, it's a totally different kind of edge you're working toward. Generally I just go till I get the burr, then get rid of it. When touching up an edge (I use a single bevel) I alternate about a dozen light passes on either side, it should need very little maintenance compared to a shaving-edge. The cutting effect is only limited to how coarse you can cleanly achieve, I haven't gone beyond 60 grit. Properly done it'll immediately catch and bite on a manilla rope and in some cases actually require a lessening of pressure to cut most easily. That, to me, is the signature of a well done coarse edge. Not that it will choke if too much pressure is used, but it should have enough saw edge that it cuts best with speed, or a light draw edgewise. Mine will casually cut through free-hanging denim or Carhartt canvas without needing the tip to dig in. For press cutting it works poorly, but will shave some hair off my arm without apparent snagging - it must have some respectably sharp edges between the peaks. Sorry I can't give you any better criteria, I basically just tried it out on different material at different grits. A last note, just like with a fine edge, a coarse edge should throw back no light when looked at edgewise straight into the grind direction, except for a pinprick of light here and there. If it's throwing light back all along the edge, you're not done. I have used primary/secondary bevels in the past, but these days I get by with a single bevel and it makes touch-ups a lot easier.
HH

 

[me2]

I uses green rouge polish just to get rid of burr, just to clean toothed edge from whatever part of metals it has - at least this is my theory.

I do my regular sharpening - whittling hair is what I am looking for at the end.

But I do not know what to looking for in case of this coarse edge. What is your criteria, when you know you are done?

Thanks, Vassili.

If you want to drive yourself nuts, you can use the hair whittling test on coarse grit sharpening too. I explored this a while ago, and practiced until I could whittle beard hair with a 220 grit waterstone finish, using something similar to your table top wooden angle guide.

Inspired by Heardheart, I practiced with a file until it would shave the hair on my arm. People's eyebrows really go up after showing them that trick. I used a Handifile, single cut on one side, double cut on the other. This is only useful on relatively soft knives. This file will barely scratch most of my knives. Either I need more practice (most likely issue), or better steel (would be nice), since both these coarse, sharp edges take more time than doing it by progressing to finer stones.

For beginners and veterans alike, a Coarse/Fine combo India stone will give an edge that will whittle my beard hair with no finer stropping or stones needed. With the right steel, my 220/1000 grit Bear waterstone will whittle my wife's hair with no further refinement. Just because it isn't polished to a high grit doesn't mean it isn't sharp, and it can be done in minutes with some practice.

 

[nozh2002]

If you want to drive yourself nuts, you can use the hair whittling test on coarse grit sharpening too. I explored this a while ago, and practiced until I could whittle beard hair with a 220 grit waterstone finish, using something similar to your table top wooden angle guide.

Inspired by Heardheart, I practiced with a file until it would shave the hair on my arm. People's eyebrows really go up after showing them that trick. I used a Handifile, single cut on one side, double cut on the other. This is only useful on relatively soft knives. This file will barely scratch most of my knives. Either I need more practice (most likely issue), or better steel (would be nice), since both these coarse, sharp edges take more time than doing it by progressing to finer stones.

For beginners and veterans alike, a Coarse/Fine combo India stone will give an edge that will whittle my beard hair with no finer stropping or stones needed. With the right steel, my 220/1000 grit Bear waterstone will whittle my wife's hair with no further refinement. Just because it isn't polished to a high grit doesn't mean it isn't sharp, and it can be done in minutes with some practice.

It is pretty clear to me that whittling hair will not work to check if coarse edge is ready. I read abut three finger test on Spyderco forum (in Off topic subforum) - but not yet tried it myself.

It is important to know what too look for to understand if you done or not - how to test if following procedure you actually succeed. For me whittling hair is that kind of Quality Metric which indicate that I am done. Should be something for coarse edge too.

Thanks, Vassili.

 

[nozh2002]

Little off topic but important warning.

I found that I have respiratory problem every time I use DMT 120 grit stone. It is not easy to notice, but I use it a lot and finally connect my cough to use of D8XX before that. So now I put piece of plastic glass between my face and this stone and do not have this problem any more. So it is not only work as grinder but as well pollute similar. Please, be careful.

Thanks, Vassili.

 

[HeavyHanded]

It is pretty clear to me that whittling hair will not work to check if coarse edge is ready. I read abut three finger test on Spyderco forum (in Off topic subforum) - but not yet tried it myself.

It is important to know what too look for to understand if you done or not - how to test if following procedure you actually succeed. For me whittling hair is that kind of Quality Metric which indicate that I am done. Should be something for coarse edge too.

Thanks, Vassili.

If you're using the three finger test to check for burr removal, it works fine even for a coarse edge. Only problem is it won't reveal a wire edge should the burr line up perfectly with the edge. A combination of good lighting and the three finger test works pretty well though.

I agree, it would be nice to have a metric for defining coarse edge properties. From my POV, all knife edges fall somewhere between draw cutting and press cutting. The hair whittling or hanging hair test are really only checking for performance at the extreme end of a polished edge (me2's results notwithstanding). Checking performance subtleties for every grit edge from 30,000 (or smaller) down to 120 (or larger) grit would require a huge battery of tests with repeatable pressure and movement parameters. All other variables being controlled for, I suspect there will be detectable differences for every grit change, not to mention differences in how certain metals respond to different edge preparations. Lacking this sort of test, all you can do is compare performance informally as you go through different edge treatments.

HH

 

[me2]

It is pretty clear to me that whittling hair will not work to check if coarse edge is ready. I read abut three finger test on Spyderco forum (in Off topic subforum) - but not yet tried it myself.

It is important to know what too look for to understand if you done or not - how to test if following procedure you actually succeed. For me whittling hair is that kind of Quality Metric which indicate that I am done. Should be something for coarse edge too.

Thanks, Vassili.

Why will it not work?

 

[hardheart]

I think it depends on how coarse the edge is. I tried to whittle at 100 grit and barely caught the follicle. I've never tried it with a 60 grit or filed edge, though they shave arm hair well. I wouldn't call a 220 edge highly refined, but my 'coarse' edges are coarser. It becomes a question of what does the test show, more than what the edge can do. Whittling hair may be an impressive display of edge refinement when it is done with a mirror polished edge finished with 0.10 micron diamond, or 0.03 micron linde powder - but maybe it isn't so impressive when it's also done at 800 grit, then 500, then 220. It's why I don't like the paper slicing videos, they don't show anything. I can slice pages out of a phone book with a knife sharpened on a cinder block. You have to start pushcutting some distance from the point of hold before cutting paper starts to mean something about edge polish.

I would guess just arm hair or cleanly slicing paper would be good enough for coarse edges. At this roughness, it isn't hard to spot burr remnants, especially with a low power loupe. These are quick to apply, slicing edges, meant for work, not show. Whittling & pushcutting aren't even the intended uses, so such tests shouldn't be used imo. The most refined thing I can think of is slicing rolling papers with no snags/tears, but I just did that with a filed edge.