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