Knife Sharpening For The Microscopically Anal
 

Didn't have much to do today so sharpened some of my kitchen knives. Really didn't have much to do, so examined the edges under a microscope, before and after different operations, using red marker pen to determine the portion of the bevel that was being ground in each step and comparing to the angle at which the blade was being held.

I learned that most of my knives have been sharpened at about 30 deg (angle between stone and nearest flat of blade) - so, total included angle 60 deg. I re-sharpened a couple at about 20 deg (total included angle 40 deg). Will be interested to see how well the more acute bevel holds up.

I also learned that when a blade is steeled using too much pressure, the edge gets many jagged protrusions where tiny bits of metal have been torn partly off. Under microscope it looks a bit like a ragged saw blade. The blade superficially "feels" sharp, and cuts well at first, since the jagged bits are acting like an invisible serrations. But after a little while, the jagged bits round off or smear away, leaving the dull edge. Exasperated ("dammit I just sharpened this thing"), the user reaches for the steel again, and so on.

If a blade is sharpened properly, on a stone, then steeled very lightly - hardly any more pressure than the weight of the blade - under microscope the edge is smooth. That edge not only feels sharp, it really is sharp, and stays sharp longer than the faux-sharp edge that has been abused with the steel.

Finally, even if an edge that has been carefully stoned and delicately steeled, the bevel still looks rough under the microscope, with the metal furrowed not smooth. So I'd like to try stropping my blades for a smoother finish.

You know, stropping on a leather band, like barbers used to do. Anyone do this to their knives? Any tips to share?

What a looser. Where are the microscope images and the spread sheet???

;)


George

Kitchen knives, I usually use a steel, since Cindy dulls them quickly when cutting on a plate.

Hunting & pocket knives here get an Arkansas oil stone

Stropping? Why? Do you plan on shaving with your knives?

Not being overly facetious here...it's just that the fine edge used on a shaving blade would mean a quick dulling if used as a knife.

Here is a pic. Not a good one, I simply put the point and shoot up to the microscope's eyepiece. You can see the red marker I applied after stoning, then where the steel contacted the bevel. This edge is not one of the "steel-abused" ones, so it is fairly smooth. But it could be smoother. And see what I mean about the furrows in the face of the bevel?

http://forums.pelicanparts.com/uploa...1229921752.jpg

FYI this is a Victorinox-Forschner, 8" cimeter (curved) slicer, stamped blade, been a workhorse for nearly 20 years. It is sharp, most people who felt the blade would say its "like a razor" or some such comment, but from the microscope shot you can see it could be smoother and sharper.

Sacrilege!

Make her use a nice cutting board in the kitchen.

Many grades (grit equivalent) of stones or diamond honers out there. Some good systems for maintaining proper angles as well.

Interesting...I've never seen microscopic before...still, the edge of a shaving edge is extremely thin...has to be. Thus easily dulled.

Cindy's kitchen remodel resulted in a couple of pull out cutting boards. One can always hope...;)

there is a distinct difference in the type of edge you can get on a "tough" knife vs a "strong" knife.

lets use the lan-cay mil-spec model M-9 for example: the edge you can put on this type of DO-ALL knife will not last long cutting elk. this is because its rockwell hardness is high. this lends itself to an edge that doesnt last long. but this knife unlike others can be used to pry with and generally use it as a crowbar without breaking.

when you use a simple stanley box cutter blade you feel as if you could shave with it. maybe you can but im not. anyway the reason is these are lower on the rockwell scale and take an edge very easily.

so when you buy a high buck henkel knife set for your kitchen what are you getting???? a middle of the road metal as far as rockwell hardness that will lend itself to taking an edge easily. but you aint gonna pry open ammo boxes with it without breaking it.

have heard many stories of G.I.'s over the years shaving with various bayonets. after owning quite a few bayonets and sharpening the hell outta them with stones or diamond blades i have failed to get one EVER to a razors edge. its your face if faced with shaving with juan.

now from years of playing with knives and bayonets and machetes heres how you sharpen juan.

just VIZUALIZE cutting a piece of cheese(queso). take knife blade along stone or diamond blade at 22 degrees. nothing more nothing less. do one side and then repeat at 22 degrees sharpening it over stone or diamond blade just as if you were slicing a piece of cheese.

take piece of paper in left hand, draw knife thru paper with right hand if it makes a clean cut it is sharp. if it doesnt repeat 22 degree cheese slicing sharpening process until it draws thru paper effortlessly.

That's a cool pic. Thanks for sharing.

My routine is a fine diamond stone to start if the edge is in bad shape. I skip this for just a touch up. Then an arkansas oil stone, then a few trailing alternating strokes on a leather. The leather smooths the edge and makes it cut better.

I've never tried a steel. I might give one a try sometime.

jt

? So a harder metal dulls faster than a softer metal?

I would think that this has more to do with the fact that the blades are thick (to be strong) and therefore are harder to put an acute angle edge on (probably a requirement for shaving).

But I'm no expert, educate me.

YES EXACTLY ! "A HARDER METAL DULLS FASTER AND IS HARDER TO KEEP AN EDGE ON"!!!!

lets use dive knives as another example. dive knives are tools period. they are used about 10 times a year, not washed of salt water and lanquish in their scabbards until next years dive. thats why they are stainless or titanium. most divers let all their gear lanquish and then wonder why they have an out of air situation. back to dive knives.........salt will eat them. even high buck ones will start gathering surface rust over a time period. bayonets are usually parkerized which is ok if ya clean it. both types are tools. pry cut slice screw hammer etc. the high rockwell allows them to survive.

if ya take yer henkel or kobi/kobee whatever sushi knife out into say iraq or afghan or underwater diving its not going to last when prying ammo boxes open, cutting rope cardboard over and over. it has a better edge granted but it will break in half when enough lateral pressure exerted upon it.

sooooo...............lets take a look at an axe and a meat cleaver. an axe has a thick frontal area vs a meat cleaver. an axe is obviously strong(harder) while a meat cleaver has a knife like frontal area. the meat cleaver will keep its edge longer than the axe for obvious reasons.

now how do ya get the best of both worlds???? pretty damn tough to do. if yer gonna cut meat buy meat knives and then edges will last.

if ya want to open ammo boxes, slice pelvic bones of elk deer etc, get a bayonet style knife, the design difference once again is obvious.

if ya have watched "how its made" on dish tv they had a good show on making knives. the final op on a knife surprisingly is NOT sharpening it on a stone or a diamond.

what they do is run the edge both sides along a very large POLISHING BONNET, just like you would use to say polish car parts or bike parts to bring out the edge and to make it look purty to the consumers eye.

oh and another note. if ya have a dull knife and cut yerself and you were to look at the cut under a microscope it would have ragged edges. these knife cuts take a long time to heal. thats why scapels are razor like in design to make a clean incision and the wound will heal quicker.

many G.I.'s of all nations recognized this and never sharpened their bayonets in the event of having to involve themselves in one of the more grusome aspects of war.............."THE FIXED BAYONET CHARGE"!

many bayonets came with "BLOOD LETS". these allowed a soldier to remove the bayonet after plunging it into enemies body quickly. another trick was the soldier shot a round also as he was withdrawing bayonet from enemies body to facilitate quicker removal and move onto next poor soul.

Did a little reading.

Apparently for blades that will be used for "push cutting" (like a razor, chisel, or plane), you want the most polished edge possible - without the grooving, roughness, and furrows on the pic above.

For blades that will be used for "slicing" (like a kitchen knife), some say you want a little roughness, others say you still want as smooth as possible, and yet others say you want some roughness if slicing foods with soft interiors and tough exteriors (soft tomatoes, say). Personally I have a serrated knife for cutting tomatoes.

i am a wuss...i bag up all my kitchen knives every holiday season and let a pro sharpen them. once a year. i then just straighten the edges with my steel. i use a wooden board for veggies, and a plastic one for the meat...no cutting on the counter or plates. not even a sandwich. i pay $1 per inch.

for my hunting knives i use a spiderco system that puts a shortlived razors edge on the blades. i have a "knives of alaska" that has a tool steel that holds up well. i run the blade thru my broadhead sharpener 3-4 times per ELK.

no leather strap. the micro edges flip too easily on food, or animals. i leave that for the barber. but i may try it on broadheads.

no rambo knife no care

:D

I'm glad you guys understand the fine points of knife sharpening. Most folks know just enough to put a lousy edge on and otherwise ruin the edge profile. Professional sharpener guys are worth their fee.

I just picked up a Kershaw "assisted opening" knife. It's the size smaller than the Leek. I think it's called "Scallion." Wonderful product.

I have both a leek and a scallion. My first scallion went to my brother-inlaw. I used the Leek for a couple of years and ended up giving it to a guy in Romania that invited us over for a whole day to try wines, many of which he made. Both of these had the electro-coated rainbow titanium look.

My replacements are standard grey coated, but they are beatiful knives. It's funny, I can't tell you how many times both of those knives have made it past security. I'd say that 3 times out of 4, they are missed at x-ray.

My understanding of the strop is that when sharpening a knife (especially when dragging the blade away from the edge across the stone) you can get a very sharp, but very fragile edge that initially cuts well (but is very thin and flexible), and easily breaks off when in use, but as long as it is in place is the leading edge and where the sharpening takes place. The strop removes that fragile edge and allows the blade to be sharpened properly. My recollection is that a strop does not sharpen a blade. My understanding is that a steel does not remove material like a stone does, but rather realigns the edge (those microscopic serrations that get folded over with use) that the stone put on the blade.

What the heck is a "steel"?

a steel is that rod you see chef running a blade over. it only re-aligns the edge. it flips over with use, at a microscopic level.

i dont have the real skill to work it like a french chef. i poke the end into a kitchen towel, approximate the 25 degree angle, and stroke away.

http://forums.pelicanparts.com/uploa...1229996807.jpg

I think traditionally a steel is a smooth round bar of hard steel, that is used solely to re-align the edge.

But nowadays most consumer steels have file-like grooves so that they actually remove metal, if you apply enough pressure. So you can actually sharpen an edge with a steel, but (as I mentioned in the first post) it doesn't do a very good job of sharpening. At least, not in my hands.

I bought a diamond-coated steel once. What a waste of money, the coating wore off after a few months and I threw the thing away.

Couple more, then I'll stop, this is getting a bit geeky . . .

This is a 6" Henkels slicer, about 20 years old, maybe the first decent knife I ever bought. It is rather dull. Kind of the "wife's knife". She likes to toss it in the sink to rattle around w/ the dirty dishes. Not as dangerous to the dishwasher (me) as you'd think because that sort of abuse dulls the knife very quickly. We have "discussed" this many times in 18 years but at the end of the day, her attitude is that machines should function indefinitely without care, maintenance, knowledgeable operation, or indeed any attention at all.

Here's the "before" pic. Can see the edge has been steeled in a forlorn attempt to slow the dulling.

http://forums.pelicanparts.com/uploa...1230007518.jpg

After stoning, 20 degrees, on medium stone w/ oil. I only own one stone w/ medium and fine sides, makes decisions easy.

http://forums.pelicanparts.com/uploa...1230007723.jpg

After stoning, 20 degrees, on fine stone w/ oil. I use olive oil because it is handy and I am lazy. The grooving seems a bit finer and tidier.

http://forums.pelicanparts.com/uploa...1230007790.jpg

After very lightly steeling, with the "un-grooved" part of the steel, to smooth off any little jaggies. Its interesting to see how just some very light steeling is easily visible.

http://forums.pelicanparts.com/uploa...1230007888.jpg

Alas, in a week or two, this nice Henkels slicer will be a butter knife again. I think I'm going to buy the wife a Cutco, "just for you, dearie".

ok, which one of you guys wants to sharpen my knives?

John, You sure your wife isn't named Cindy? I guess since we sharpen them, they figure is no big deal to use knives as they see fit.

Randy...for $10 per inch of blade, as mentioned earlier? Bring 'em on up...:D Or better yet, I could teach you. Really, sharpening a knife isn't all that hard...

I love seeing that last round of pics jyl! You can clearly see the bead that forms on the edge when you hone one side more than the other. The trick with getting a REALLY sharp edge (yes, even with your pig sticker knife) is creating that bead, then snapping it off. If you can do that, then you can make the hairs on your arm/face literally JUMP off when you shave. THAT'S what "hair popping sharp" means. I can do it with my kitchen knives as well as my daily carry "tactical" Benchmade knife. Oh...it's D2 tool steel, very high Rockwell hardness, and it won't go dull quicker than a softer blade, despite what my Aridzona friend might claim.

thought that was ONE dollah per inch....

actually, I have a motorized water stone - Tormek machine... great for sharpeninghttp://forums.pelicanparts.com/uploa...1230015194.jpg

Nice - I am still waiting for the spread sheet though. A few 3D micro roughness scans would be nice too. ;)

While this work earns you a lot of respect from the nerd crowd here, do not think that microscope pictures of your knife edge will change the spousal knife abuse.

Off to buying a stone ...

George

kinda enjoying this thread...sharpening knives is something most men who are semi-handy enjoy...I've tried all kinds of different techniques and stones and have ended up buying a Chef's Choice 3 stage electric sharpener (@ $120) and absolutely love it...won't fool with anything else - fast, easy, and leaves a consistent good edge.

The thing about motorized systems are they can be indiscriminate and fast. This can result in significant metal loss, more than required for regaining an edge. You can also lose too much in one area. I like the Lansky system. Multiple grades, stone and diamond available. Consistent angles without sacrificing anything.

+1 for the Lansky...I bought mine to keep broadheads "tuned up" and use it to do the same with my knifes just before hunting season starts.

Easy to use and you get a constant angle to your knifes edge

I went to the Lansky site and watched the video. Looks pretty cool. I might be afraid of getting careless and cutting the fingertips on the hand holding the hone. Also seems designed for normal-sized knives? Suppose you are sharpening a 14" slicer, do you have to reposition the clamp?

I learned a trick for measuring the angle. Take a square piece of paper (e.g. a post-it note) and fold along the diagonal, then fold again. That's 22.5 degrees, close enough to 20 degrees. Or, fold in thirds and get 30 degrees. And so on.

I need more explaining on this comment. I could see if you wrote "tougher", but "harder" means higher tensile strength which would seem to me that it would keep an edge longer.

i am with david on this one..life is a give and take.

harder metal is more difficult to hone and edge into it, but once there will hold it longer.
softer is easier to sharpen, but looses the edge faster.

at least this is how my feeble mind grasps it.

cliff

Can you give the exact model or post a pic. I checked on this and there are several three stage jobs from Chef's Choice out there. If these work well for you, I may go for them. I have little time to fiddle with my knives, including microscope analysis, but like them sharp ...

George

I'm also eyeballing a Chefs choice sharpener for my Christmas gift to myself.

At that price it seem like the model 120, they also have a 130 that appears to just to be a newer version of the 120?

For a manual system the Spiderco looks pretty nice too.

I'm bumping this thread for George and I.


I have the triple stones and the ceramic rods and all the blah, blah, blah... but I can't get into the knife sharpening ritual.

I would much rather have a machine that would give me perfect edge in a few minutes.

And if a pro charges $10 an inch the $120 Chefs choice will pay for itself many times over.

Anyone else using one?

ok think about this. after shooting 3 x 4 elk i went to town with my lan-cay m-9 bayonet on certain aspects of elk field dressing.

when i received m-9 it had a nice edge from factory. nothing to write home about and you sure as hell werent shaving w/it.

i took my diamonds and started with fine then moved to extra fine. 22 degrees jes lak slicing some cheese.

anyway in very rapid time its edge was gone trying to cut hide away. this is normal for a high rockwell hardness blade. the m-9 is a everything knife. pry this pry that, hammer on it etc. therefore it needs high rockwell to survive its appointed duties.

after m-9 blade started fading away we then moved into elk with stanley box cutter blades. these lasted better because of their ability to HOLD AN EDGE vs the m-9.

now lets pry open an ammo box with yer wifes henkel set of knives. sharper than hell and you can shave with them. buttttttt..........when you pry open ammo box the blade breaks in 2. the m-9 with the dull blade prys open ammo box no problemos.

so the higher the rockwell hardness the edge is not going to last as long.


another example. hk g-3(hk-91) bayonet. once again high rockwell. has bloodlets same as m-9 bayonet. SOLINGEN STEEL! the best there is. you can go to town putting an edge on it, but you will never shave with it and if ya cut open a few cardboard boxes the edge you just put on with be duller than a butter knife. the tip will remain pointy and it will hurt if stuck with it..............but you aint cutting elk hide away from meat with it very long.

another example: buck 6" blade, black handle black leather case model. you can put an edge on that knife that will last a fair amount of time. you can bash a deers pelvic bone with a rock and it will take it. try the same on an elk and you are asking for it to break due to thickness of pelvic bone btwn the 2 animals.

there is no perfect knife that is a multi-functional tool. cut meat you need it sharp. break bones/pry open ammo boxes / cut hide etc. you need a different knife.

a bayonet is the middle of the road to do everything. thats how there designed. it aint the best but it will do and you can resharpen it and thats why they include stone attached to scabbard.

I have the Chef's Choich. Mostly you use stage 3, for a quick job on the edge. Stage 1 is used when the knife is dull. Stage 2 is non motorized, and used to make a "special" edge very very good for cutting meat.

Unless the knife is DULL, I use only stage 3. It is a very light ceramic edging tool.

Found at http://www.knife-expert.com/rockw.txt

"THE C SCALE

The scale used for testing the hardness of knife blades and
other hardened steel items is the Rockwell C scale. C scale tests
use the diamond Brale and the full 150 kgf major load. The
theoretical maximum hardness is infinity, which would be 100 on
the Rockwell C scale. Infinite hardness is of course impossible,
and few substances test very much over RC 70. The range of
hardness for functional knife blades is mainly between about RC
50 and RC 63. Most good sport knives test around RC 58 to RC 62.
Blades toward the high end of this range tend to be good at edge
holding, but very difficult to resharpen. Blades toward the lower
end are easier to sharpen, but may not stay sharp as long,
especially under demanding use.

Because Rockwell hardness testing yields a number, it seems
absolute and precise. However the test has important limitations
often overlooked by both the marketer and the consumer. First of
all, a single test is only valid at the point of testing. Any
blade, especially one that has been hardened by hand and eye,
should be tested at several points.

Second, the Rockwell test is a surface hardness test. It
cannot reveal anything about the hardness of the interior of a
steel item.

Third, to quote from Wilson Instruments, maker of Rockwell
hardness testers, "... the Rockwell test is a measure of the
resistance of a material to permanent indentation. Indentation
hardness is not a fundamental property of a material. However,
reliable relationships have been established between the various
tests and important properties of materials -- for example,
tensile strength and machinability. Furthermore, indentation
hardness has become one of the more reliable controls of the heat
treatment and quality of manufactured parts."

Do you know what the model number is?

I have been looking on the web and Chef's choice makes a couple of three stage sharpeners.

Here is a link to pdf comparison chart from the manufactures site:

http://www.chefschoice.com/docfiles/qrfelec.pdf