Improving sharpening skills

With a 600 DMT stone which leaves a fairly coarse edge finish, a Coyote Meadow (CPM-10V/62.5 HRC), South Fork (S30V/60 HRC) and Caffrey/Blade MEUK (52100/58 HRC), all could readily be made to push cut (90 degree orientation, no draw) newsprint at one inch from the point of contact between the index finger and thumb which held the paper.

I sharpened them multiple times trying different methods to get the crispest edge, the one inch performane was the lowest, at best the averaged about 1.5 inches, and if I was really careful it would extend out to two inches which is the best I have seen in a while, the paper is really floppy at that distance, going under one inch was trivial, you could bring the knife down sloppy and it would shear through the paper.

On an interesting note, the MEUK was the hardest to form clean, it tended to burr really easily on the coarse stone, it was very difficult to get a crisp edge, any bit of slop on the stone and a wide burr would be produced which would be visible to the eye with careful examination under light. The hardness quoted is a heat treating range, the other two blades are HRC tested by Wilson individually.

The edges were cleaned of debris on leather loaded with chromium/aluminum oxide with three passes per side with three passes per side before and after on plain leather. This didn't polish the edges significantly, they looked the same under magnification, it just removed debris. The Sharpmaker medium stone is *way* finer than the 600 grit DMT so it should get better paper results.

I still didn't get any of them to push cut toilet paper though they all sliced it easily.

-Cliff
 
Ok.... how!! Honestly, I can get a knife well under 100 grams on poly now thanks to you, but I find it literally impossible to get consistent push cuts even a millimeter away from the point I hold it on newsprint. I want to know exactly what you're doing different, clearly it must be something considering that performance is close to razor blade like...

Inquiring minds want to know!

Push cut toilet paper... Jesus H. Christ

Edit: Also, know that I'm not questioning your methods (well I guess technically I am since I'm asking about them) or doubting you, I just find it amazing that someone can get a knife that sharp. I know I've been a bit of a pest lately especially on this subforum :)

PS I'm going to have to start sharpening with harder knife soon... I can only get a few cuts in with the Opinel before it dulls. I brought it below 50 today, with no detectable burr even on the microscope, but it only lasted for a few cuts in newsprint and printer paper, then it was back down to 75ish. Its disheartening.
 
ghost squire said:
Push cut toilet paper...
Click to expand...

To clearify, I can't actually do that, I don't even know if it is possible, but you have to have something to aim for and that is the current goal. The biggest problem with sharpening, in fact the only problem, is getting rid of the burr. Once the edges actually meet, which is easy, all you have left to do it cut off the burr, the only difference between a sharp edge and a dull one, assuming the edges meet, is the extent of the burr.

Fooling around with the above blades had me realise that maybe the most ideal method is a combinatino of Clark's and Goddard's. Goddard leaves the high angle burr strokes on the edge and Clark grinds them off. I think ideally you would stop just short of grinding them off and thus there is the barest hint of the obtuse burr-evel on the micro-bevel. This prevents the burr from reforming.

With the 52100 knife, every time I cut off the burr-bevel it would reform a burr. I sharpened it a dozen times trying to get it to form clean with no success. What was interesting was that the burr would move along the edge, only about half of the edge would be burred, about half of it would be clean.

It has to be the action of the knife on the stone, I figure it isn't enough movement down the stone and there is too much side movement, or simply too much pressure as there was too much deformation and not abrasion, you can feel the stone bite in evenly on a proper stroke. I don't think this is the ideal performance of the steel, by the way, this knife is just too soft.

In regards to difference in push cuts on paper, the problem with "tests" like these is that they are not well defined. I would bet we are not exactly doing the same thing, because 1mm distance is trivial to achieve. To clearify, when I was push cutting at 1+ inches, when I brought the blade down, the paper could buckle and thus I had to raise the edge back up and try again.

The only way you will succeed in making a push cut is if the paper is perfectly aligned and so is the blade and you apply the force consistently, at large distances the paper is floppy this isn't trivial to do. I'll try to get some video's next week so you will know exactly what I mean. Can you make a push cut if you do it fast, this is *MUCH* easier, for example the same blades which would do a 1-2" push cut slow, can do them at about 8" if I bring the blade down fast.

Try both snapping the blade down with a pop of the wrist, and then raising your arm and bringing the blade down. Both of these are much easier to make push cuts with than slowly by hand.

...it only lasted for a few cuts in newsprint and printer paper, then it was back down to 75ish.
Click to expand...

Blunting is *HIGHLY* nonlinear, it is extremely rapid at the onset, and then tapers off dramatically, it fits well to a log scale of material cut, which means it is a power law relationship. As a rough scale, do a small amount of cutting, and then keep doubling it to see the same amount of blunting, note how this means that after just a few rounds you have to cut an insane amount of material to see anything significant happen.

-Cliff
 
The biggest problem with sharpening, in fact the only problem, is getting rid of the burr. Once the edges actually meet, which is easy, all you have left to do it cut off the burr, the only difference between a sharp edge and a dull one, assuming the edges meet, is the extent of the burr.

Fooling around with the above blades had me realise that maybe the most ideal method is a combinatino of Clark's and Goddard's. Goddard leaves the high angle burr strokes on the edge and Clark grinds them off. I think ideally you would stop just short of grinding them off and thus there is the barest hint of the obtuse burr-evel on the micro-bevel. This prevents the burr from reforming.
Click to expand...

Interesting... I wonder if it would be possible to literally cut off the burr, say with a razor blade at a slightly higher angle then which it was last sharpened. Though this wouldn't accomplish what you're saying as it would likely remove the entire burr. Damnit, I wish I had a better microscope so I could see what kind of edge this would leave at a very small scale. Theoretically if you did it at the right angle and the burr was big enough (relatively speaking of course) it might be possible to only cut off part of it. Unfortunately this would require extreme accuracy. Tomorrow if I have time I'll try out cutting the burr...

And what if you simply smushed the burr flat to the blade at a slightly higher angle than which it was sharpened on that side? Without actually moving the edge on it. If you used a very flat and hard surface it would definately reduce the amount a burr dulls an edge by decreasing the width of it. This might also prevent the forming of another one!

Another way somewhere between these two would be to get a hard surface with an accurate, sharp angle on one side and hold the edge at an angle to it and move it parallel to sort of scrape off the burr.

In regards to difference in push cuts on paper, the problem with "tests" like these is that they are not well defined. I would bet we are not exactly doing the same thing, because 1mm distance is trivial to achieve. To clearify, when I was push cutting at 1+ inches, when I brought the blade down, the paper could buckle and thus I had to raise the edge back up and try again.

The only way you will succeed in making a push cut is if the paper is perfectly aligned and so is the blade and you apply the force consistently, at large distances the paper is floppy this isn't trivial to do. I'll try to get some video's next week so you will know exactly what I mean. Can you make a push cut if you do it fast, this is *MUCH* easier, for example the same blades which would do a 1-2" push cut slow, can do them at about 8" if I bring the blade down fast.
Click to expand...

Ok, that would be fantastic. A picture is worth a thousand words, and a video is a thousand pictures LOL

Blunting is *HIGHLY* nonlinear, it is extremely rapid at the onset, and then tapers off dramatically, it fits well to a log scale of material cut, which means it is a power law relationship. As a rough scale, do a small amount of cutting, and then keep doubling it to see the same amount of blunting, note how this means that after just a few rounds you have to cut an insane amount of material to see anything significant happen.
Click to expand...

Very true, I watched the Fikes DVD yesterday where he does a hemp rope test. The superfine edge disappears with a few cuts, but it stays sharp for about 400-500 cuts. I now have sympathy with what you have to do for some of your knife reviews :eek: I think my hands would blister up and shrivel away after a single test.

Can you make a push cut if you do it fast, this is *MUCH* easier, for example the same blades which would do a 1-2" push cut slow, can do them at about 8" if I bring the blade down fast.

Try both snapping the blade down with a pop of the wrist, and then raising your arm and bringing the blade down. Both of these are much easier to make push cuts with than slowly by hand.
Click to expand...

I'll try those out tomorrow, me so tired!

Thanks for clarifying the toilet paper thing. I was going insane because I can barely slice the kind I have. Of course... I do use single ply toilet paper apparently constructed of fiberglass and nylon thread... Its pretty hard on a knife edge! LOL If theres a blade out there that can actually push cut toilet paper (which I don't believe a razor blade can even do?) I would worship it as a deity.

Thanks for responding :thumbup: :)
 
ghost squire said:
If theres a blade out there that can actually push cut toilet paper (which I don't believe a razor blade can even do?) I would worship it as a deity.
Click to expand...

Ben Dale and Alvin Johnston probably have made several edges worthy of your worship. I feel bad for the iconoclast that feels duty-bound to save you.
 
I just checked out the world's greatest sharpener page... I can see there is much that I must learn about sharpening. But according to it, none of them were able to push cut toilet paper. Ben Dale's entry was almost able to push cut a paper towel though.

BTW who is Ben Dale? He seems to be known around here for extreme skill at at sharpening.
 
I think Cliff was refering to cutting off the burr with a hone. I don't think trying to slice it off with a razor blade would leave you with a very good edge. It's probably worth a try just to see though. I will not be doing it but if you do let us know what happens.
 
ghost squire said:
Very true, I watched the Fikes DVD yesterday where he does a hemp rope test. The superfine edge disappears with a few cuts, but it stays sharp for about 400-500 cuts. I now have sympathy with what you have to do for some of your knife reviews :eek: I think my hands would blister up and shrivel away after a single test.

Hi, Ghost Squire

If you watch the video again, the rope cutting was stopped at 500+ cuts on the 3/4 inch manila, more for lack of time than lack of sharpness on the blade's part. IIRC, every hundred cuts, I'd take the blade and cut the rope using only one hand on the handle to make sure it still snicked through the rope with the particular sound a sharp blade makes. If you mean by 'superfine' edge' the edge on the cleaver that cut Greg's arm hair without touching the skin... then the superfine edge did vanish rather quickly. But at 500+ cuts, the edge could still shave and slice very thin newsprint (Shotgun News, to be exact) with only one or two tiny spots on the edge hanging up a bit. Same was true with a later knife that I tested on rope WAYYYYYYYYYYYYYYY beyond what was shown on the old vid... to the point where I said, enough is enough. Blade would still shave and slice the thin newsprint. Superfine edges are fun to try to get, and to play with for sheer sharpness... but they're soon gone once the knife is cutting something really abrasive. Cliff is absolutely correct when he states that blunting is nonlinear. My objective when heat treating a blade and shaping it... both blade geometry and edge geometry... is to make something that will remain very sharp (shaving at a minimum) for a long time AND (just as importantly) not chip or bend in very hard use. The jungle honey I was swinging with both hands had an edge just as fine as that on the cleaver. In fact, all blades in the video had exactly the same edge. I can makes edges sharper, or tougher... but most of my work goes out the shop door with the same 'one size fits all' edge.

Cliff,

I understand that Thom also sent you one of the DVD's. I notice in the above posts that your results show... and it would seem to make perfectly good sense... that blades sharpened parallel to the edge would have a weaker edge due to the direction of the micro teeth. In the practical tests I've run over time, I find edges applied by sharpening parallel to the edge hold up just fine. I sharpen all my blades with a diamond hone that is run freehand up and down the length of the blade... as shown on the DVD when I resharpen the little tanto that I poked through the oil drum. I never try to hold a particular angle with the diamond hone. I purposely *change* angles (being careful not to hold the hone at so steep an angle as will blunt the edge) so that the edge is always rolled in... and a bit of the blade directly above the edge is thinned out. This method keeps a good edge geometry longer than any other method I know of short of honing the whole blade surface with each sharpening.

Sharpening with a handheld hone / stone is very easy to master once all the 'mystique' is tossed out about how difficult it is to get a good edge on a blade, And it works just as well for the 'sharpening disadvantaged' as it does for me. To illustrate this point, I'm quoting a short email that I recently received from a good friend / collector who lives in Switzerland. (Hans... I'm sure you won't mind me posting this. And even if you do, you're way over there and I'm way over here!:p Send more chocolate, by the way, if you ever want to see your knife. Bitter, if you will!)

>>>>>good afternoon jimmy,

you won't be too impressed as this is daily business for you. however, i wanted to let you know that for the first time i was able to sharpen a knife decently, using your method, i think, more or less. sandra complained that one of her kitchen knives (thin wide blade, san mai, core about 1% carbon) was "dull" - although it cut paper easily, but she has become a bit spoilt lately - so i brought my sharpening stones with me and started with a coarse stone on the very wide primary bevel to reduce the secondary bevel to almost zero, then went on with a 1000 grit water stone. after that i held the stone in my hand and ground an almost invisible convex edge until i felt a wire, which i gently removed with the 6000 grit stone, then stropped on my denims, as i didn't have a leather strop. then fun began: i shaved my forearm (looks quite stupid now), used the knife as a cleaver and cut one of sandra's paperbacks into thousands of pieces, slightly honed the edge, then made newspaper rolls. i wasn't able to cut every roll, but when the angle was right, it worked really well, and once the lower part of the roll even remained standing on the table while the upper part was cut away! as my left forearm was shaved before, i cut some hair from my head, without touching the skin, of course. sandra then told me to stop, which was a good idea as i would probably be bald without her. maybe i'll try again next weekend and take some pictures.

take care and have a nice evening!
hans<<<<<


I'm babbling. I'll stop. Need more meds. ;)

Jimmy 'gimme dat knife' Fikes
Click to expand...
 
Hi, Ghost Squire

If you watch the video again, the rope cutting was stopped at 500+ cuts on the 3/4 inch manila, more for lack of time than lack of sharpness on the blade's part. IIRC, every hundred cuts, I'd take the blade and cut the rope using only one hand on the handle to make sure it still snicked through the rope with the particular sound a sharp blade makes. If you mean by 'superfine' edge' the edge on the cleaver that cut Greg's arm hair without touching the skin... then the superfine edge did vanish rather quickly. But at 500+ cuts, the edge could still shave and slice very thin newsprint (Shotgun News, to be exact) with only one or two tiny spots on the edge hanging up a bit. Same was true with a later knife that I tested on rope WAYYYYYYYYYYYYYYY beyond what was shown on the old vid... to the point where I said, enough is enough. Blade would still shave and slice the thin newsprint. Superfine edges are fun to try to get, and to play with for sheer sharpness... but they're soon gone once the knife is cutting something really abrasive. Cliff is absolutely correct when he states that blunting is nonlinear. My objective when heat treating a blade and shaping it... both blade geometry and edge geometry... is to make something that will remain very sharp (shaving at a minimum) for a long time AND (just as importantly) not chip or bend in very hard use. The jungle honey I was swinging with both hands had an edge just as fine as that on the cleaver. In fact, all blades in the video had exactly the same edge. I can makes edges sharper, or tougher... but most of my work goes out the shop door with the same 'one size fits all' edge.
Click to expand...

Yup, I notice the ultra sharp edge on my Opinel goes away after just a few cuts in printer paper or newspaper, which I understand can be rather abrasive as well. I wasn't trying to denigrate your blades, just agreeing with Cliff that wear resistance is a non linear thing. I have no doubt that the edge on the cleaver would have lasted for probably thousands of cuts. One of the things I got when watching that video was that a properly done knife edge will last for days and days even in a survival type situation where you would use it quite a bit.

It's probably worth a try just to see though. I will not be doing it but if you do let us know what happens.
Click to expand...

I know he was talking about taking it off with abrasives, but he was having trouble with that so I suggested some alternate ways. Well I just created a burr on my Opinel with a 1,000 grit waterstone, large enough to easily feel but not large enough to see. Testing on poly thread it scored 325 grams, which is extremely dull. Then I cut, but in retrospect more like scraped, off the burr with the razor blade. It immediately flopped over to the other side, and to my dismay left a very "wavy" edge, with long rolling hills on the very edge. This should be good for slicing though LOL

I scraped the burr off the other side and repeated it with ever lightening strokes. Tested it on poly thread and it scored a 125. Not terrible, but definately not good either. I suppose in the field you could use a razor in lieu of a steel though...
 
Jimmy,

I mailed the DVD out to Cliff a week or two ago, but his particular neck of Newfoundland is a geographical oddity - it's exactly 24 weeks away from everywhere.
 
ghost squire said:
Interesting... I wonder if it would be possible to literally cut off the burr, say with a razor blade at a slightly higher angle then which it was last sharpened.
Click to expand...

Probably, if the razor blade was made out of HSS. An abrasive, essentiall cuts steel similar to how steel cuts wood.

And what if you simply smushed the burr flat to the blade at a slightly higher angle than which it was sharpened on that side?
Click to expand...

A common technique to removing burrs is to smash them off like that, what is problematic is that not all steels respond the same. How to remove a burr on a very hard and very fine grained carbon steel is very dissimilar from a soft high carbide stainless.

I have done trials for example where I tried to strop off a burr on really fine grained easy to machine steels and then really coarse and horrible to machine steels. The exact same process gives radically different results. Try it with D2 vs 1095 for example.

Another way somewhere between these two would be to get a hard surface with an accurate, sharp angle on one side and hold the edge at an angle to it and move it parallel to sort of scrape off the burr.
Click to expand...

Carbide scrapers can be useful here on large visible burrs.

If theres a blade out there that can actually push cut toilet paper ...
Click to expand...

The WGS results are on decent blades, but HSS would give much better results, plus you could hone to 4/5 degrees to radically shift the cutting ability and amplify the sharpness. I don't doubt that it could be done.

OleyFermo said:
IIRC, every hundred cuts, I'd take the blade and cut the rope using only one hand on the handle to make sure it still snicked through the rope with the particular sound a sharp blade makes.
Click to expand...

This is the part that a lot of people miss, you have to test for sharpness, without some kind of criteria for juding when to stop it is hard to tell what, if anything, was accomplished by looking at it from the outside and comparing it to something you have done. It is similar when blades are tested only on one type of media, cut rope but never chop wood, or mash into a car door, but never cut anything. It is fairly easy to get a blade which does one or the other, but the really impressives ones can cut pretty much anything for a long time and take very little damage even on hard contacts.

In the practical tests I've run over time, I find edges applied by sharpening parallel to the edge hold up just fine.
Click to expand...

Experiment trumps theory, it doesn't matter how logical and sound the reasoning, if in reality you see something else the theory has to change, either adapt or be completely rewritten if necessary. This is the benefit to discussing matters in public, you say what you know based on what you have done, then somone points out it doesn't match what they have seen and you figure out why and hopefully learn something. It is nicer done in person as then you can settle any fights over a bottle of scotch, because in the end you will either resolve your differences or forget what you were in conflict about anyway, which just means somewhere down the road it will come up again and you need to break out another bottle which is never a bad thing.

I sharpen all my blades with a diamond hone that is run freehand up and down the length of the blade...
Click to expand...

What grit is the abrasive? Do you leave the edge with that finish or do you buff / polish it? Are these in general fine grained low alloy steels?

I never try to hold a particular angle with the diamond hone. I purposely *change* angles (being careful not to hold the hone at so steep an angle as will blunt the edge) so that the edge is always rolled in... and a bit of the blade directly above the edge is thinned out.
Click to expand...

I do something similar with most blades but run the blade on the hone the other way, unless I am in a hurry to resharpen in which case I just micro-bevel. Most of my blades have very shallow convex bevel due to this, all the working ones do, I generally fix angle the ones I do comparisons on so it removes one of the points of variability. I usually try to include at least one freehand comparison as well, but the results tend to be less precise because of slop in the grinding, of course the more of that you do the more consistent the results would become and eventually it would be just as consistent as v-rodding.

Sharpening with a handheld hone / stone is very easy to master once all the 'mystique' is tossed out about how difficult it is to get a good edge on a blade...
Click to expand...

The blade shape and general nature of the steel goes a long way, the main problem that people have in general is that most knives are made with really hard to grind steels which are often left soft and the edges thick and obtuse. Working with these to try and create a sharp edge and then doing the same on a very thin, acute and hard low alloy knife steel is night and day, they sharpen about the same as they cut. The first time I used one of the better forged bowies (Ray Kirk) it was pretty extreme how it handled compared to the normal production knives of similar shape. At the really high end it starts to be more of comparing a knife to a knife-like object.

-Cliff
 
The WGS results are on decent blades, but HSS would give much better results, plus you could hone to 4/5 degrees to radically shift the cutting ability and amplify the sharpness. I don't doubt that it could be done.
Click to expand...

Maybe when I get a hold of some M2 saw blades I could crank out a bunch of simple blades for this purpose to your specs? Something like oversized razor blades perhaps.

Thanks for the info on burrs.
 
John Frankl said:
What are the chances of a lowly professor stuck in Korea getting ahold of one of those Fike's DVDs:)?

johnfrankl@yahoo.com
Click to expand...

Hi, John

Chances are a lot better on the DVD than on that magazine article I promised to send... and which, despite me reminding him on about a bi-weekly, my buddy still hasn't brought back.;) Nope, I didn't forget!

Email me at OleyFermo@aol.com and send mailing details.

Jimmy
 
HSS at full hard would be pretty much ideal for a sharpness comparison, however sending around stock HSS blades would likely induce a lower rate of returns than $0.50 cent Olfa blades, generous offer though.

-Cliff
 
You must log in or register to reply here.
Back
Top