Sharpening for different purposes

ThinkOfTheChildren

ThinkOfTheChildren

Joined
Jul 7, 2000
Messages
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Whenever I sharpen a blade I just can't help taking every little detail all the way to the end. This means that I end up with an extremely smooth edge. This edge is impressive for shaving, showing off, and some tasks but it fails miserably at others. I sometimes find my "scary sharp" blades sliding off of denser mediums.

So what kind of edge (coarse, medium, fine) do you recommend for the following applications?

Every day carry (twine, envelopes, cardboard, tape, etc)
Self Defense
Kitchen use
(Help me think of other categories)

Also, how much would your answer change depending on the steel. My blades with CPM440V seem to have much more "bite" than my blades with 154CM. So how much compensation needs to be done?

Situation specific:
Gunting CPM440V - Self Defense - Coarse, med, or fine?
BM940 154CM - EDC - C, M, or F?
Lum Chinese VG10 - EDC - C, M, or F?

Any thoughts appreciated!
 
Because of the new software I know that over 40 of you have looked at this thread. Not one of you has an opinion here?!?

BTTT
 
for 940, I like a "scary sharp" edge for about 80% of the 3.4" blade and for the rest (portion closest to the handle), I prefer M or C to start cuts, or to cut through twine or tougher materials. Takes the place of serrations.
 
I don't really go for a polished edge too often. I like a little "tooth" to my blades. For instance, my Buck110 came very sharp, but it was not polished. That little extra bit of bite from a rougher sharpoening definitely helps in cutting certain things. I assume that this is what people refer to as micro-serrations.

The only steel I've used so far, that seems to be least effected by polishing, is BG-42. That stuff cuts no matter what you do to it!!! I wish all my knives were BG-42.
 
I have found that somewhere between medium and fine works best in any situation. After getting the edge sharp on a medium grit stone, I'll either give it a few passes on a fine stone or strop on bare leather.

Paul
 
I'm a sucker for a polished edge, don't know why. Maybe because it took me so long to be able to do it...

After reading the Juranitch book on sharpening, I don't know if I believe in a "coarser" edge. I think there might be "furrows" that aren't polished out, but I'd be surprised if that makes a difference. The knife that cuts me the most (and the easiest) is my straight razor, go figure.

Having said that, I'm probably one of the least qualified to render an opinion, so I welcome other comments.
 
I find slightly coarse to be the best on everthing--except shaving your arm to see how sharp your knife is.

The only knife I keep a polished edge on is my Lum Chinese...it's just too pretty not to.

Keep in mind that you can get a coarse edge two ways: just sharpen with a coarse stone, or sharpen to a polished edge and then just do some very light swipes over a coarse stone. The latter seems like a better idea to me.
 
I like to go from a medium stone, strait to a crock stick to finish up. The crock stick is not aggressive enough to polish out the medium stone, but does a good job creating a nice "toothy" edge.
 
I don't have much of an opinion about the different steels, but I do have oen about different mediums.

For Urban Commando EDC, I think that either a coarse or polished edge is fine. By Urban Commando I mean envelopes, coupons, 6-pack rings, tags from clothes, occasional card board, etc.

If you cut cardboard, wood, or rope more often, go with the coarser edge.

For kitchen knives, a polished edge will be best. Most kitchen cutting is push cutting so a polished edge works best there. If you have a knife you use to slice with, make the edge coarser.

For fighting, the theories are kinda all over the place. A polished edge is more durable and will cleave into flesh better. That si what I'd go with. Though I think that polished versus coarser edge ona fighting knife is really a nit picky knife knut point, and not one that really matters all that much. a coarser versus polished edge probably shows little difference when stabbing a target! And when you are swinging liek mad with a blade, a coarse and a polished edge will make someone bleed. But, since I (and youI assume, after all, we're Bladeforumites!) am a knife knut, I'd go with a polished edge on a fighter.

Once compromise that I have heard works well is using a coarse stone to set the edge and then stropping right there. You get the micro-serrated blade that is polised. I hear it can shave hair yet is rough enough for more fibrous materials. Experiment to see what you prefer best.
 
I prefer a polished edge on everything. But the one thing that is being overlooked in this discussion is the concept of sharpening different angles. I like the stockman pattern, and if I want to adapt to different uses, I can sharpen the three blades to three different angles. This is one drawback to the current popularity of single blade one-hand openers. If you remember Alvin Johnston on rec.knives, he was a big fan of this approach.
 
The general sharpening guidelines I follow:

- Make the edge as thin as possible for best performance, but thick enough to not chip, indent, or roll inordinately for my hardest tasks.

- Make the edge as coarse as possible, provided it still performs adequately for my most often-performed tasks.

What I'm going for is the highest performance, without the edge being damaged during hard use. My overall approach is obviously blade, steel, and use-specific. What I want to do is bring out the very best of whatever particular steel I'm using, for whatever particular job. Given two otherwise identical knives being used for the exact same tasks, one in ATS-34 and one in M-2, they will be sharpened differently based on the first rule. Given two identical knives in the same steel (say, ATS-34), but being used for different tasks, they will be sharpened different based on rules 1 and 2. I think people who are buying knives with expensive steels, but not really drawing the performance out of those steels in their sharpening strategy, are to some extent wasting their money. Not only is it nicer to get the best performance possible, but it's a fun challenge to tease every last drop of performance (while maintaining robustness) out of each particular knife.

Since I find I more often prefer good slicing performance, I tend to like to leave the edge at medium grit, never fine. Occasionally, I'll do a combo-grit blade: I polish the entire blade, then carefully rough-up the last 1.5" of blade nearest the handle. So the front of the blade is polished for push cuts, but I have a great slicer at the back. I prefer this approach to the partially-serrated approach, because even though the blade is at different grits, it still functions as a single plain edge when necessary.


Joe
 
From what I have seen, I prefer to go with polished edges. Saying this, I do not believe that you need an 8000 grit Japanese waterstone to have a functional edge. I conducted a few little tests and from what I have seen a knife cuts materials of all kinds better than a course edge WHEN PUSH CUTTING. I do not saw back and forth with my blades, and if I cannot push cut the material at hand then the edge needs work. I once made a swing with a Buck fixed blade sharpened on a "V" sharpener, it went right through my sweatpants and split my knee open(on accident of course). This had a course edge on it. So as far as fighting knives go, I don't think it really matters. My personal opinion would be to sharpen the knife till it will shave hair, but don't go nuts and start cutting free hanging cigarette paper:D
 
Lots of great responses here, so I'll be brief. [post script, I lied, then I typed]

I land on the side of those who, after learning how to sharpen, find that having maybe one or two serrated knives around is plenty, and I don't buy serrated stuff anymore as I rarely need serrations for what I use a knife for typically.

Bottom Line:
I find a Medium or Fine diamond stone induced edge, one that fairly cleanly and is grabby/toothy, to nearly always be the right tool for me, for daily carry.

Talmadge's post is good stuff. Makes sense.

My daily carry stuff has either a 20 degree or 25 degree final edge. Depends on knife and steel. And on where I was in my learning curve when knife was purchased. I put more 25 degree bevels on early on, now use 20 usually. Same for hunting knives. Bigger blades (5" to 12") get same to steeper angles depending on intended use.

Machete's & Axes:
Edge angle on my machete's is steep, but I do it on a bench grinder and they'll still get shaving sharp, pretty rough and they scrape plenty of skin while roughly shaving, and I leave probably a 30 degree (not included) on those since I chop with them. My hatchets and axes are of course convex, done on same bench grinder (a 220 grit coated cardboard wheel followed by rouge-loaded hard cardboard wheel), and they may be 35-40 degrees, and sometimes they even shave a little hair (grab/scrape) when I'm done. They sink deep and edge has lots of backing.

Big Blades:
Stuff from 5" up to 12"... depends. I keep a convex edge on the biggest stuff, 9" to 12" bowie. Use rubber backed 2x4 and 400 to 600 grit sandpaper for big convex blades (thanks Cliff Stamp). Stuff 5" to 6", alternatively, I can get done on Lansky in two moves of the jib, no problem blending the angle as some have reported. Or I step up to the 220 grit grinding wheel and free-hand it, and that kind of automatically results in a sort of convex final edge like the Sebenza's (only not that sharp yet!).

Kitchen knives:
I use an Chef's Choice EdgePro 120 motorized sharpener. That means all kitchen knives have a two part bevel, I think at 15 then 20. Unit has 2 diamond wheels, coarsest is for initial beveling. Medium grit puts a grabby edge on. Third wheel is a nifty fine stopping type wheel, and it is very good at removing the burr. Nifty. Kitchen set is just a decent set of Henckels knives, not custom. My wife would kill me if I bought a bunch of high end/high dollar custom kitchen knives (Boye, Phil Wilson, etc). So for these Henckels, I don't feel bad about using a motorized unit...if I remove a bit too much steel, well, then I'm just that much closer to "having" to buy custom. ;) I use a Henckels steel to keep edge straight between sessions on the EdgePro. Would they push cut better if polished? Probably so. Do they push/chop through veggies fine? Yes. Do they slice meat? Absolutely. Are they optimized? No, they aren't. Are they sharper than 99.9% of the other people's kitchen knives? Yup. Are they sharp all the time? Yup. Am I somewhat lazy with respect to optimum edge on kitchen knives? Yup. And seriously, I can run 12 knives across that machine to renew to a grabby, scrapey/shaving edge in about 6 minutes, so they are always sharp. 30 seconds or less per knife. So they stay sharp. It's actually fun, not work. I have to resist using the machine.

Daily Carry Folders (5 days/week/job):
I nearly always use a Lansky for my rotation of daily carry folders. I have a worn-out Medium grit Diamond stone that I use for final edge. Probably about like a new to somewhat-worn Fine diamond. Diamond cuts fast, diamond leaves a shaving edge that is grabby, toothy, and that works great for daily carry. It's not often that I grab for a serrated blade to cut, say, tough synthetic cord or a particularly gnarly vine around the yard, as I don't have it with me and get through this stuff fine with toothy diamond edge. Daily carry to work 5 days a week is one of my customs or Sebenza's, all worn medium diamond final edge, most at 20 degrees, some at 25. I rotate them. If it doesn't shave it is put into resharpen spot on coffee table for something to do while watching the tube.

Defensive Folder:
If I know I'm headed to say the French Quarter or somewhere else where I want a more for-purpose defensive knife, I grab the Emerson Mach-I, with chisel grind on wrong side and all, and partly serrated, since this one has a good lockup and part serrations and a great handle for sure grip. YMMV. Emerson is reprofiled to 30 degrees included, except around the tip where the production line hammer-head at Emerson free-handed the last 1/8" to about 50 degrees, and I'd have to remove too much metal to get rid of that. The 710 gets chosen in this defensive carry mode often too. Medium worn diamond again.

Working/Weekend/Around the yard carry:
I have 4 BM AFCK 800's and 3 BM 710's, 2 Spyderco Starmate/Terzuola's, 1 Spydie Military ... most picked up used for good prices. That is the "work force". Bunch of Dozier fixed blades too. Most of them are always really sharp and ready to go, one folder stays in mountain bike seat bag, one folder and a 6" fixed blade stay in garage, etc. I grab these to work around the yard. They all get a medium to fine diamond for final edge. I don't use the Spydie 204 much, just for serrations, but when I do, I stick with the gray ceramic for making burr, and just use the white ceramic to remove the burr and finalize the edge. (i.e. I don't polish many edges).

Overall, if the 710 had a stouter point, that would be about the perfect production working knife for me, dropped/swedge point, enough point, enough belly, recurved back edge, 4" blade, trustworthy Axis lock, inexpensive enough I won't cry if I chip the edge or lose it somehow (haven't lost a knife yet! Not even fishing. Knock on keyboard... shouldn't have typed that... that's my a$$). I like the 710 for a defensive folder also since it's legal to carry 4" around here and I like Axis.

Polished Edges:
If I wanted one, I have a worn-out Fine diamond Lansky, and then I can either finish the edge on the rouge-loaded fiberboard wheel and use that like a very fine grit grinding wheel (polishing really), or futz around w/ white ceramic 204 sticks (not often). The rouge wheel leaves a very polished and convex edge like a NIB Sebenza, although I sure can't get them that perfected...yet. I'd love to watch those guys in Chris' shop do the edges.

Ok, I lied. It wasn't a short post. :D
Hi, my name is Rob, and I'm a knife-o-holic.
 
Situation specific:
Gunting CPM440V - Self Defense - fine?
BM940 154CM - EDC - M
Lum Chinese VG10 - EDC - F?

This is something I have studied at great length.

What I have found is that the CPM 440V steels work great at the Ultra fine level of polish as they shave very well and are still quite grabby.

I as a rule use my edges at a 'fine' or Ultra fine level of sharpness.

I find that step three on the Shapmaker gives a great all round edge.

I accept that is some situations the medium stone finsih can work better, but in such situations I prefer a serrated edge.

One good knife is my 154CM MOD CQD DD. The plain edge is honed to an Ultra fine edge at 20 per side and the serrations kill anything else! I as a rule dislike a combo edge more than anything, but for this knife it is perfect.
 
Originally posted by The General
What I have found is that the CPM 440V steels work great at the Ultra fine level of polish as they shave very well and are still quite grabby.
Click to expand...

Ah, forgot to comment on 440V. Only stuff I have is from Spyderco, Starmate & Military. Think both were of vintage that was at Rc56-57. They take a very grabby edge and shave nicely with my worn out fine and medium diamond stones.

I have a Darrel Ralph neck knife in 420V that is the same way... this thing is just super sharp and grabby and pops hair. I dunno...either Darrel did something really good in heat treat, or I just get lucky and get a really hair jumpin' edge every time.

The CPM stuff, when heat treated by someone who does it right, has a very nice, fine grain structure, attributable, I think, to both Vanadium content AND to the Particle Metallurgy technology, which helps ensure that you don't get big gnarly vanadium carbide "boulders" like some guys get out of D2. You'd think this might make them not take a grabby/toothy edge, but the grit of stone is what sets the grabbiness, not grain structure. So to me, that says that with CPM's, you can get what you want...fine, refined shaving edge or a grabby edge. And they hold it through a good bit of slicing.
 
I agree, it takes a fair bit of practice to get the sharpening with CPM 440V 'just so'. I think the Vanadium causes the graby edge and the steel is easier to sharpen to a normal fine edge than a high performance Ultra Fine like I like. The trick it to get is symetrical on the 204 step 4 and then place the ultra stone on the 204 and get that edge super sharp.

I love the fact that CPM440V is very rust resistant and holds an edge very very well. I have not had problems with toughness, but then I use a can opener as a can opener.;)
 
The more obtuse (greater) the bevel angle and/or the thicker the blade, the coarser I want the edge. I mostly grind my blades thin, primarily releaving the blades down to 15 degrees. Then I put a relatively smooth finish edge on them ending with a ceramic rod. If the knife design or function does not allow that thin an edge I like to leave the edge coarser. This achieves agressive cutting on a thicker edge. I'm guessing that a thick, smooth edge allows the material that you are cutting to conform itself to the edge and sides of the bevel with a very even pressure distribution. The lack of stress concentrations makes it more difficult to start the sort of zipper-action of cutting. A coarse edge creates areas of stress concentration where the material separation can begin easily. A thin edge always achieves high stress concentration and doesn't need the coarser edge.

Try sharpening a bayonet with a file and you'll see what I mean. For defensive purposes I would always go for a rougher edge. It goes through meat and clothing much easier and surer.
 
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