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No I think you can see you heartbeat (every time the blood squirts out)
Sorry couldn't resist...
Murray Carter "Three Finger Sharpness Test"....what?
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No I think you can see you heartbeat (every time the blood squirts out)
Sorry couldn't resist...
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I also find that I can get a pretty good idea of the condition and sharpness of an edge just by looking at it and seeing how the light glints off the very outer most "edge" of the edge. The more glint you see at the very edge the less sharp it is. Ideally you do not want to see any glint that is separate from the rest of the edge, it should appear to be one continuous grind ending in a "zero point" looking edge. I use this method to visually inspect an edge that I am working on, sometimes there will only be one small spot along the edge that needs more work and I can spot it just by looking this way.
...Does that make sense to anyone else, or is it just me?
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Makes perfect sense to me. It's what I rely on, probably 95% of the time. The more knives I sharpen, the easier it becomes to 'see' when the edge is right (or very nearly so). The absence of reflected light from the edge is what I look for (I call it an 'invisible edge'). Beyond that, I usually check shaving sharpness on my forearm, and make repeated slices through some paper, making sure that the whole edge, from ricasso to tip, will slice easily and repeatedly (that's the burr test; never lets me down). If the edge has enough 'bite' to catch the skin, I'll see that when I shave hairs from my forearm. Sometimes leaves little red cut marks up & down my forearm.
I stopped checking edges with my fingertips (deliberately, anyway
) a LONG time ago. I use 'em for too many things, to risk the inconvenience of cuts getting in the way. I had a blade on a folder SNAP shut on my index and middle fingers of my right (dominant) hand a few years ago. Clipped a nice flap of skin from the tip of each finger, bled like a stuck pig. I had a dinner date with a friend that evening, and never felt so ham-fisted trying to cut my steak without using these two fingers (and getting the bleeding going again; I'm sure the other restaurant patrons would've been real impressed).Isn't it amazing what can be done with a Sharpmaker and a lot of practice. I wanted to test my Delica and started cutting cans, top to bottom, 15-18 cuts per can. I gave up when I went through most of a 24 pack of cans and the Delica would still shave hair off my fingers.
I don't use MC's test much, but the best way I've found to do it is to back bevel with a water stone in the 1000 grit range, then micro-bevel with the Sharpmaker on the medium brown stone flats. This edge passes the 3 finger sharpness test every time, in no small part due to my fingers still being wet from the waterstone.
Also, everyone's body is different. For example, arm hair shaving tests are a bit different for me. My arm hair is very, very fine. A blade that is barely shaving sharp for my arm hair will make hairs fly off other men's arms like it was a power lawnmower.
Any test based on one of your body parts could potentially have consistency problems from person to person.
Any test based on one of your body parts could potentially have consistency problems from person to person.
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You have to keep in mind the tools he's using. Different grinding media will produce slightly different results. I believe he uses a 6000 grit JIS water stone to finish, which equals about 1500-2000 grit CAMI (I think). I too wondered about his "three finger sticky" test. Many of my coarsely finished knives will catch immediately on finger pads (approx 120-220 grit), but I figured there's no way this is the standard he's working with. As I get into the middle grit ranges 400-1200 the edges become less sticky and then at 1500 -2000 they become "sticky" again. I'm pretty sure at 2000 I'm getting back to his sticky edges (I believe this is approx 1 micron), and as I progress into the sub micron the edges become less and less sticky while becoming increasingly adept at shaving and pushcutting (cutting with pressure alone). Somewhere in this range (1 micron - .3 micron) an edge looses pretty much all of its functional "teeth". I go to great pains to maintain a grind pattern even down to 2000 grit - I do not want to strop it away w/ the burr, and I don't. These edges push cut, shave well, even facial hair, but still have enough "catch" to initiate cuts on smooth and dense weave type materials. But below this level which I estimate at 8000grit JIS or smaller, this ability diminishes. Not positive, but I'm pretty sure this is what Murray Carter is talking about. It seems he does nothing extreme to strop his edges and perhaps this is why, he doesn't want to "wash" his grind pattern away. Eliminate the burr and leave it alone. BTW, anyone that has his videos care to explain his thoughts on "angular microserrations" and their affect on cutting?
HH
HH
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Not to complicate an already complicated process (albeit a fun one) My tests and expectations vary by knife.
My Acies is hair whittling scarey sharp for most people, My Hinderer is a different kind of sharp. Different expectation, methodology and testing method.
I imagine IF I pulled out ALL my knives they would fall into maybe three (3) categories or so of sharpness/testing/sharpening method.
I don't know if this holds for everyone but makes sense to me.
I assume for the sake of this discussion I/We would use the category of Wicked Sharp for using a three finger test.
Then Working edge knives category might be slice paper or rope as a test.
Then the Third category might be the "How frigging Sharp can I make this thing" for that..... Splitting the AtomI dunno
My Acies is hair whittling scarey sharp for most people, My Hinderer is a different kind of sharp. Different expectation, methodology and testing method.
I imagine IF I pulled out ALL my knives they would fall into maybe three (3) categories or so of sharpness/testing/sharpening method.
I don't know if this holds for everyone but makes sense to me.
I assume for the sake of this discussion I/We would use the category of Wicked Sharp for using a three finger test.
Then Working edge knives category might be slice paper or rope as a test.
Then the Third category might be the "How frigging Sharp can I make this thing" for that..... Splitting the Atom
I dunno
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Being that I've been doing a lot recently to learn Murray's method (someday I should buy the video even though pretty sure I have it worked out at this point), I did some scrounging around in his newsletter archives and came up with this:
He uses it straight off the 1000 grit stone, so in addition to ongoing visual inspection, this is meant to help detect burrs, wire edges, completeness of grind to the apex, overall level of refinement, etc. In his own words if it feels 3 finger sticky and can shave armhair, then its OK. There may be a great deal of truth to the notion of some "toothiness" required to pass this test - stropping on newspaper seems to leave the grind structure basically intact and induce little if any "rounding". That said, my hair whittling edges certainly catch on my finger pads when doing this test. I suspect a highly polished edge done at a more obtuse angle might not feel very "sticky" and that brings up another point - Mr Carter grinds to some fairly acute angles - based on what I've seen from his videos probably in the mid to upper 20s for inclusive edge bevel.
He uses it straight off the 1000 grit stone, so in addition to ongoing visual inspection, this is meant to help detect burrs, wire edges, completeness of grind to the apex, overall level of refinement, etc. In his own words if it feels 3 finger sticky and can shave armhair, then its OK. There may be a great deal of truth to the notion of some "toothiness" required to pass this test - stropping on newspaper seems to leave the grind structure basically intact and induce little if any "rounding". That said, my hair whittling edges certainly catch on my finger pads when doing this test. I suspect a highly polished edge done at a more obtuse angle might not feel very "sticky" and that brings up another point - Mr Carter grinds to some fairly acute angles - based on what I've seen from his videos probably in the mid to upper 20s for inclusive edge bevel.
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just to put some things in perspective, not bashing anyone.
a couple years ago i was very involved in the "in the kitchen" subforum of KF, lots of great infos there regarding japanese style kitchen knives, sharpening, waterstones etc.
lots of very competents users, and a couple of sharpening "gurus" with different methods and point of view ... it was fun.
back then Mr carter was notorious for a couple of things, first for making very thin and very sharp blades, then he was also notorious for leaving some serious burrs on his blades.
a couple years ago there was a sharpening "competition" with dave martell as a judge the verdict was that Mr carter's knife was hands down the sharpest, but also that his knife had a serious wire edge that failed after some use and flopped right when dave put it on his plain leather belt (on a sander). keep in mind that an aligned wire edge can be very sharp, it'll cut your skin just like a clean edge. how could you discern the difference ?
so the 3 finger test as a way to find a wire edge , not so much imho.
a couple years ago i was very involved in the "in the kitchen" subforum of KF, lots of great infos there regarding japanese style kitchen knives, sharpening, waterstones etc.
lots of very competents users, and a couple of sharpening "gurus" with different methods and point of view ... it was fun.
back then Mr carter was notorious for a couple of things, first for making very thin and very sharp blades, then he was also notorious for leaving some serious burrs on his blades.
a couple years ago there was a sharpening "competition" with dave martell as a judge the verdict was that Mr carter's knife was hands down the sharpest, but also that his knife had a serious wire edge that failed after some use and flopped right when dave put it on his plain leather belt (on a sander). keep in mind that an aligned wire edge can be very sharp, it'll cut your skin just like a clean edge. how could you discern the difference ?
so the 3 finger test as a way to find a wire edge , not so much imho.
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I have to say two things to the above -
First, the toughest thing re Murray's method imho is removal of burrs and prevention of burr formation on the 6000 grit stone. I commented in the current thread on edge-trailing that I find it difficult to impossible to control or remove burrs using an edge-trailing motion on most types of media. Powered methods seem to have less of an issue, and waterstones (for me) fall into the "not too tough but still watch your backside" category. Had mixed results initially, but can now reliably whip up burr-free edges using this method, however cannot usually verify this without using a loupe. Doesn't surprise me that some burr/wire edges make it out his door.
I read some of the discussion around that competition, and so approached Carter's method slowly and with a lot of observation. All to easy to whip up a real "nice" edge that's all wire.
Second - I cannot tell much in terms of detail using the 3 finger test. Now if I tilt the blade and use my three fingers to press the side of the bevel, rest them on the opposite side and pull up a touch, brush along the sides etc, then I can find out a bit more. Lightly clamping down and giving a wiggle tells me little, though I still do it hoping I'll develop a bit more intuition with repetition. I'm not a big fan of using four or five different cut tests to figure out where my edge is at. If this method can be made to work for me I'll be pretty happy, but am skeptical I have the hardware to pull it off, esp after all the beating my fingers have taken over the years.
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Edge leading or edge trailing has little to do with burr formation, burrs are mainly influenced by grinding pressure followed by steel quality and heat treat quality.
The three finger test is just like using your thumb but with three fingers at the same time. You feel for the same qualities in the edge as you would with other touch methods.
The three finger test is just like using your thumb but with three fingers at the same time. You feel for the same qualities in the edge as you would with other touch methods.
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Yes and no - Verhoeven noted (and I've seen it plenty of times as well) that the direction the edge is moving in plays a large factor in how much metal is left behind, as with an edge leading stroke some of it gets smeared off between the blade and the abrasive. Edge trailing frequently raises a burr faster and larger than edge leading, despite edge leading probably removing more metal/pass (all other things being equal - steel, heat treat, type of abrasive). Stubborn burrs sometimes won't respond at all to more edge trailing passes and have to be removed with some form of edge leading movement (powered devices aside- speed plays a role I'm not equipped to explain but plastic flow might have a role).
No doubt excessive pressure leads to excessive burr formation, however there is a minimum threshold of pressure required (for an abrasive to function) to remove a burr as well. When you think about an abrasive particle as a cutting tool, imagine its a chisel cutting into a blob of cold taffy or similar material, and consider the effect of approaching the metal from different angles and what will be left behind after the cut is made. Even hardened metal is ductile to some degree.
At least this is what I believe I've observed...
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Edge leading strokes are cutting into the surface imperfections, even if only at a microscopic level.
Edge trailing strokes allow the edge to ride over microscopic imperfections in the stone.
If you can remove the burr by:
-stropping edge trailing
-stroking through wood
-then stropping with an edge trailing stroke
You may see better results than if you were sharpening with a edge leading stroke.
It's been said here before, but think of a sand box. If you stroke a knife through sand with an edge leading stroke you will dull the edge, but if you stroke the knife through sand with an edge trailing stroke you will sharpen the blade. Make sense?
Edge trailing strokes allow the edge to ride over microscopic imperfections in the stone.
If you can remove the burr by:
-stropping edge trailing
-stroking through wood
-then stropping with an edge trailing stroke
You may see better results than if you were sharpening with a edge leading stroke.
It's been said here before, but think of a sand box. If you stroke a knife through sand with an edge leading stroke you will dull the edge, but if you stroke the knife through sand with an edge trailing stroke you will sharpen the blade. Make sense?
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I look at it like clay,
My thoughts and theories on the burr and its formation seem to be slightly different than most others. I don't see it as a problem but just a final stage that with proper technique can be worked past. Problem is, its not easy to do and can take more effort to learn to do it right than it does to pick up a strop and quickly finish without frustration.
Verhoevens experiments on sharpening is very good but it was a test on a limited sample. Although there were conclusive results the results were individual to the experiment at the time.
My thoughts and theories on the burr and its formation seem to be slightly different than most others. I don't see it as a problem but just a final stage that with proper technique can be worked past. Problem is, its not easy to do and can take more effort to learn to do it right than it does to pick up a strop and quickly finish without frustration.
Verhoevens experiments on sharpening is very good but it was a test on a limited sample. Although there were conclusive results the results were individual to the experiment at the time.
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Specific analogies aside, we probably view it in a similar light. To my way of thinking, removal of the burr is 85-90% of the entire job. Everything up to that is setting the stage - the better the stage is set, the better the finished edge. A lot can go wrong if one has to flip the burr too many times. Stropping brings its own load of variables...
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Again, maybe yes and maybe no. When you drag an edge across an abrasive a couple of things happen - the material being carved off of it is more prone to hang on and build up at the apex (this is heavily influenced by speed I believe - seem to recall something about elongation and ductility dropping way down as the testing speed increases - which explains why some machine grinding (edge trailing) produces far less burr than comparable processes at hand speed).
The apex is also more prone to distortions. If you do hit some large grit or swarf, it will press into and possibly shred the apex, creating a notch with distorted metal to either side - edge leading will give you a ding, but not the distortion to either side. Straight razor guys have proven and documented this effect pretty well. True enough they're working with a very thin and comparatively unstable wafer of metal, the basic principle is the same. I agree that edgeleading will exaggerate the highs and lows on your grinding surface (or at least do nothing to dampen them), but it also leaves behind a "cleaner" cut. The fact that a burr can be formed either way tells me the grind goes clear to the apex. There may be a grit value "penalty", but at the higher grit values this cannot amount to much. The sandbox analogy isn't that accurate - on a stone most of the loose abrasive and swarf is smaller than the grit - most of what you move against is fixed unless you allow the stone to choke up. Both methods have you moving on the tops of the abrasive particles, just a question of how they go to work.
Stropping with an edge trailing motion isn't the same thing - strop particles can move and flex quite a bit as they cut - they're not going to dig in, so they're far less likely to leave behind any remnants. If they bite off more than they can chew, they'll simply roll with the motion. They are however more likely to round the apex as they pass free. Think of it as the tiddliwink principle. If there's enough pressure to polish metal, there's enough pressure for it to bounce up as it clears. A hard stone isn't immune to this either as abrasive particles and swarf are constantly being generated no matter the method. To borrow a little from the sandbox analogy - sprinkle some sand on a 2x4 and backdrag a metal ruler or similar over it - you'll see sand dancing up and away from that edge as it passes over. Does this matter in the real world- probably not, but then such is likely the case for the edgeleading sandbox analogy as well. Both have pros and cons.
Also, I don't pretend to have any answers here and obviously one uses what works - there are many ways to put an edge on metal. I'm not entirely averse to edge trailing, I am determined to understand Carter's method as well as possible (with the possible exception of his 3 finger test) and maybe even make it my go-to technique just for how damn fast it is.
That said, to me it needs a lot of extra care to not whip up a wire edge - there are no free lunches.
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Not sure I'm all about his method, but there are few reasons why I'm so interested (at least recently I have become interested). I already use waterstones, already have adopted his scrubbing fore and aft style of lower grit grinding, am already getting good results with my 4000 and 6000 grit Kings, don't appreciate what compound stropping does to my edges, and while I do enjoy freehanding, don't like to camp out while doing a knife or two. The draw of being able to maintain my knives with a stone and some newspaper nearly as fast as I can currently strop on loaded leather is very appealing.
I've taken a good hard look at what he's doing and have some pretty good background with other types of sharpening. I've gotten about half a dozen knives to casually swat through TP using the belly of the blade, easily cut same with just a small amount of draw, and haven't picked up my disposable razor for nearly two weeks (maintaining a goatee without making my face red ). I am able to get these results using my standard methods, but no where near as fast. Still, burrs and wire edges seem to be a pitfall of the method and need to be looked out for.
All in all I'm doing OK, but additional insight is always welcome, thank you very much for the offer.
HH
I'm really fascinated with this thread. I'm pretty new to sharpening but my whole life I've always used my thumb with a light swipe perpendicular to the blade to judge sharpness. After many many years you can just kinda tell how sharp a knife is by how much it bites into the pad of your thumb. Once it reaches a certain point of sharpness, can you really tell any difference past that point? What is the ultimate objective anyway?
For me, a knife is a tool to actually cut something I need to cut. Not my arm hair, not toilet paper, etc. For example, I field dressed 3 deer this past season with a cheap Gerber knife right out if the package and it cut through that deer flesh like butter. Afterwards, I sharpened it beyond the point it came out of the package because I can tell it has more bite on my thumb now. I'm sure it isn't as sharp as some of you can get your knives but for me it is more than sharp enough.
I have 200 dollar knives that don't feel any sharper. They look a lot nicer but they will all cut about the same.
What's interesting is people into woodworking have a similar bug. They (and I) will take great pride in holding tolerances of 1/64th an inch or less when in reality the wood will naturally expand and contract WAY more than that in the course of the seasons. Those tight tolerances are nice but they don't really matter. I kind of look at sharpening the same way. At some point I just have to say to myself it is sharp enough for what I need it to do.
I'd love to feel one of the blades sharpened by some folks on this forum to see what "sharp" means to other folks. Maybe I'm really missing out in life. I don't mean that sarcastically. I really am wondering if there is a dimension of sharpness that would blow my mind.
For me, a knife is a tool to actually cut something I need to cut. Not my arm hair, not toilet paper, etc. For example, I field dressed 3 deer this past season with a cheap Gerber knife right out if the package and it cut through that deer flesh like butter. Afterwards, I sharpened it beyond the point it came out of the package because I can tell it has more bite on my thumb now. I'm sure it isn't as sharp as some of you can get your knives but for me it is more than sharp enough.
I have 200 dollar knives that don't feel any sharper. They look a lot nicer but they will all cut about the same.
What's interesting is people into woodworking have a similar bug. They (and I) will take great pride in holding tolerances of 1/64th an inch or less when in reality the wood will naturally expand and contract WAY more than that in the course of the seasons. Those tight tolerances are nice but they don't really matter. I kind of look at sharpening the same way. At some point I just have to say to myself it is sharp enough for what I need it to do.
I'd love to feel one of the blades sharpened by some folks on this forum to see what "sharp" means to other folks. Maybe I'm really missing out in life. I don't mean that sarcastically. I really am wondering if there is a dimension of sharpness that would blow my mind.
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