From the Old Fart files

[thombrogan]

Ever practice a skill, buy lots of doodads, read lots of stuff all over the internet and then realize that you had the equipment and skills for something all along? Yeah, me too. This time, on convex edges.

Alvin Johnston and Cliff Stamp just shared the Old Farts' method for forming convex edges and it may be done with Arkansas stones, waterstones, ceramics, diamonds, crock pots, bricks, cats' tongues, just about anything. It's not a finish-safe technique, but it makes hair-popping sharp convex edges in a hurry.

Take the knife in need of sharpening and lay it flat or nearly flat on the hone. Move the knife in small semi-circles over the hone until a burr pops up (assuming you have a knife with steel that easily burrs - that should be 98-300% of your collection). Flip over and repeat. Do a few light, alternating passes over the hone at a slightly higher angle to remove the burr.

Done. Sharp. Also explains why some of us are on the ultimate hunt for a translucent Arkansas hone the width of a yacht but know people who can make atom-splitting edges with a medium India stone that's only 1" x 3".

Try it on a knife you don't mind scratching. It's that quick and simple.

I'm still keeping my EdgePro, Sharpmaker, belt-sander, and strop, though.

 

[MadDaddy]

great post, informative and funny...imaginary greenies for you

 

[lupara]

The best article I've read on stropping is under the following URL:

http://www.mhcable.com/~yocraft/sosak/convex.htm

There's a downside to stropping however - your knife won't look the same as when you first bought it...

The reason for this is that when you strop, you have to lay the blade parallel to the surface you’re stropping on (e.g. 200 grit sand paper!). This, of course, takes away material from the entire surface of the blade, and not only from the edge of it – ergo – you’re scratching up the entire blade.

Like the article says, however, that’s the idea behind effective stropping – the entire blade “reduces” itself, and not just the edge. This means that at the end of the day, a convex edge will cut as well 10 years down the line as on the first day you bought it.

The trade off is – once again - that sandpaper really scratches the fine polish on an expensive blade (e.g. on an H1, or an S1), not to mention the coating on tactical blades that have convex edges (i.e. Busse, Chris Reeve, Entrek etc.). This having been said, however, my experience (at least on fine polished blades like the H1) is that after having used sand paper (on top of two mouse pads) on the blade, I finish it up with a loaded, leather strop, which then polishes it off well enough so as to take away most of the nasty scratches, leaving a very acceptable finish to an extremely sharp blade. What I really mean is that the stropped knife still looks good...

This is my experience with stropping – I've only obtained results with this method. If someone else can give me a useful tip re coated blades, however, I’d appreciate it. For the record, I haven’t stropped any of my coated tactical blades yet, as I don’t know how the heck they’re going to look after having been dragged over hard core sandpaper. Again, if anyone can give me a tip here, I’d appreciate it! Best

 

[Bill DeShivs]

Sorry, but you guys are ruining your knives doing this.
Bill

 

[rebeltf]

Thom Brogan , that is exactly how my Grandpa's taught me to sharpen a knife.
It is great not having to use those expensive angle stick thingies
I always use my soft Arkansas and/or a tungsten rod set in antler to keep up my blades unless they are very dull then I'll start with a coarse water stone.

As for stropping , I have never needed to strop nor seen anyone need to strop after sharpening a blade , my pocketknife can shave my arm with ease.

whatever works I guess

 

[cmd]

Thanks Thom, informative and entertaining.

I learned to sharpen freehand on stones, but like you I'm not giving up my sharpmaker or loaded strop.

Hey Bill, please explain some about what you mean by people ruining knives doing this.

 

[Bill DeShivs]

CMD
Any collector value would be severely lessened by the scratches on the blade, and by thinning the edge the edge is weakened. If you simply use the knife as a tool, it is yours and you can do what you want, but laying the blade flat (or nearly so) and sharpening the blade away is simply the wrong way to do it. You can get a very good edge using accepted angles, and the edge will last longer, as will the knife blade.
I am assuming we are talking about properly ground blades, here- not Buck 110s and such that were always ground too thick.
Bill

 

[Doug C]

Bill is entirely correct that collector value would be affected appreciably by the scratches on the blade and thinning the edge weakens the edge,even polishing the scratches out of the blade can be detected unless done professionally and that will cost ya' a couple of bucks if you can't do this type of work yourself.OK.That's all. Good post Bill.

 

[Sword and Shield]

To put it mildly, screw collector value. Case 54CV? Convexed. S&M Series 13 barlow? Same. I would much rather a knife that wears out in 10 years but cuts like a laser than one that wears in 50, but isn't a good user.

Pretty is fine, but that old, worn-out stockman my G-g-grandfather carried means more to me than a perfect condition one ever would.

 

[db]

Why would anyone be sharpening a collector that they want to keep mint for resale? Pretty much any type of sharpening will devalue the knife. Anyways I thought Cliff was a flat grind with micro edge bevel kind of guy.

 

[Jeff Clark]

This is an ancient technique that I used about 40 years ago. It does not produce a weak edge unless you are working with steel that is absolute crap. As you produce a pseudo-convex edge doing this the honing angle increases as you approach the edge. Your final edge angle may very well be 30 to 40 degrees inclusive (well within conventional dogma), but the material behind the edge is thinner and curves smoothly into the blade body for reduced blade drag in use. The convex grind is structurally strong, sort of like an old gothic arch. When you are cutting thick, stiff material this is an efficient edge. I would generally strop the blade on progressively finer sand paper so that while I eliminated the original knife finish I put my own mirror finish in its place.

I abandoned this method as being over-tough and under-sharp for my desires after a year or two. My primary focus was on fighting knives and maximum slashing effectiveness. I did slash tests against leather and various types of bunched up cloth and decided that this type of edge didn't work as well against complient/fibrous material as I would like. I went through a period where I took every knife I got my hands on and hollow-ground it. I would also hone the edges down to about a 20 degree included angle. This would go through hide, cloth, meat and other fibrous matter much more effectively than a convex edge. It also only gave me durability problems on really cheap Pakistani knives (these blades were much softer than anything I have seen produced anywhere in the last 20 years). This really totalled the finish on the blades. The setup I had just wouldn't allow me to put a mirror finish on the concave part of my hollow grind.

A couple years after that my standard method flip-flopped completely. Whereas previously I had been sharpening my own knives and a few switchblades for premium clientel, I came to a point where I decided to take my act on the road and sharpen knives for a living (well at least to save money for college). I started going door-to-door sharpening knives (and scissors, and garden shears and lawn mowers). The clientel generally were not terribly critical about edge effectiveness, but they cared a lot about how knives looked. I had to come up with a method of sharpening that preserved the finish on the blades, produced a distinct and even looking sharpenning bevel, and which I could produce in a modest amount of time. For some knives the answer was to establish the bevel with a smooth file and then finish with a medium-fine oilstone. The performance was adequate for the housewives and looked right to their husbands. They worked about half as well as one of my old convexed edges, but they were prettier. I learned that for a lot of people pretty is much more important than cutting.

I have learned to take a middle course for most knives. I sharpen at around 8 or 10 degrees per side, attempting to make the bevel look neat. I convex somewhat from there using a waterstone or a belt sander. I finish with a flat bevel at just a little bit higher an angle than in the preceding. As a final step I strop a little with a fine diamond paste (being careful to keep most of my blade off of the strop). The net result is that I have a lot of knives with 3/16 to 1/4 inch honing bevels, but reasonably intact surfaces on the rest of the blade. I haven't hollow ground a saber-ground blade in years.

 

[cmd]

CMD
Any collector value would be severely lessened by the scratches on the blade, and by thinning the edge the edge is weakened. If you simply use the knife as a tool, it is yours and you can do what you want, but laying the blade flat (or nearly so) and sharpening the blade away is simply the wrong way to do it. You can get a very good edge using accepted angles, and the edge will last longer, as will the knife blade.
I am assuming we are talking about properly ground blades, here- not Buck 110s and such that were always ground too thick.
Bill

Thanks Bill, that makes a lot of sense and I mostly agree. Sharpening a knife in any way will immediately reduce the value of a collector's piece.

I only sharpen knives I want to use and put an edge on them that seems to fit with their intended role.

You may be reading a little too much into what some folks do when laying the blade close to flat on a stone. A few passes at such an extreme angle just rounds the sharp transition from primary to secondary grinds, and arcs are stronger than corners even with less material.

 

[Cliff Stamp]

You may be reading a little too much into what some folks do when laying the blade close to flat on a stone. A few passes at such an extreme angle just rounds the sharp transition from primary to secondary grinds, and arcs are stronger than corners even with less material.

The method Thom describes has the majority of the sharpening done flat to the stone, the knives look like this :

http://www.panix.com/~alvinj/HSSknife.jpg

you can see the grind marks all through the tip, at the top of the primary grind and in the actual edge. It works best with knives with deep hollow grinds, it is very *slow* on full convex/flat grinds.

CMD
Any collector value would be severely lessened by the scratches on the blade ...

They are knives users so the collector value is kind of meaningless.

You can get a very good edge using accepted angles, and the edge will last longer, as will the knife blade.

No, and no. It drastically increases the cutting ability, and increases the lifetime of the knife because it keeps the edge profile stable. Reducing the profile only decreases the cutting lifetime if you undercut the critical durability level, which this doesn't do. The last upsweep is adjusted for the necessary rigidity.

... Your final edge angle may very well be 30 to 40 degrees inclusive (well within conventional dogma),

Alvin's are much lower, the primary is usually ~3 degrees and the final about 5 for the main cutting blades, the utility knives that cut metals, scrape gaskets, open cans and such go higher, ~10 .

It takes a high end steel to take this method though, Alvin's are tempered to provide both a high hardness and strength/toughness. The same profile on many "knife steels" like S30V just collapses.

-Cliff

 

[Habeas Corpus]

Take the knife in need of sharpening and lay it flat or nearly flat on the hone. Move the knife in small semi-circles over the hone until a burr pops up (assuming you have a knife with steel that easily burrs - that should be 98-300% of your collection). Flip over and repeat. Do a few light, alternating passes over the hone at a slightly higher angle to remove the burr.

Done. Sharp. Also explains why some of us are on the ultimate hunt for a translucent Arkansas hone the width of a yacht but know people who can make atom-splitting edges with a medium India stone that's only 1" x 3".

This is the sharpening method my father used to use on his ancient carbon steel folders. He sharpened them on all sorts of surfaces including rocks and small pieces of flintstone he had found on the beach, and his knives were always sharp. As a kid I wasn't even allowed to use his knives for that reason - until, that is, I had learnt to sharpen my own knives properly ...

After reading the postings on this sharpening method on rec.knives I went hunting for some of his old folders and found one he must have sharpened some 10 years ago or so. It sure didn't look very nice with its scratched blade and its heavy patina, but it still shaved easily. I'd say it was after all those years about as sharp as my gray Calypso Jr. was when I got it new. Under a stereo microscope it showed a clearly convexed blade.

Like some of the other posters around here I wouldn't really want to use this method on some of my "nice" folders, but for my beaters I reckon this is a fast and very efficient method to get a sharp edge that holds for a long, long time. And it's one that doesn't need any complex sharpening gear at all.

Hans

 

[Bill DeShivs]

I guess I'm a neophyte, as I have only been doing it for 35-40 years, but laying a blade flat and sharpening it will give you a very sharp edge, and it may well be convex, but it weakens the blade and the edge will be too thin for any but the lightest cuts. I remember the real oldtimers doing this and it quickly wore blades down to "toothpicks." They were constantly having to resharpen because the edge was so thin. Maybe they got this method from sharpening razors (which are properly sharpened flat). A properly ground blade, with a 15-20 degree angle will cut anything you want it to and stay sharp longer. I went through the learning phase and bought all the fancy stones-up to and including synthetic ruby. Thank God the jigged gadgets were't available then, or I probably would never have learned to hand sharpen!
A properly sharpened blade will not be scratched, and correct sharpening methods do not noticeably detract from a knife's value. Over sharpening, scratching the blade from improper angles and such will. Dads make mistakes, too.
Bill

 

[Troy H]

I fully admit that it's not the best method out there -- there are many better. But this is a great method for those of us who aren't patient enough to practice the other methods.

Under good advice from a friend, I mounted the sharpening stone to a piece of 2x4. I cut the 2x4 to the angle that I want to maintain and keeping the blade vertical, I pretty much use the method that Thom described.

At least now I can get a usable edge. Other benefits? Total cost $20.

My pride and joy.

I kinda think that the "scratching" on the edge is purty.

 

[Cliff Stamp]

...the edge will be too thin for any but the lightest cuts.

Ref :

http://www.physics.mun.ca/~sstamp/knives/aj_paring.html

Sharpened flat to the stone, primary hollow grind, edge at ~4 degrees per side. Cut foods, ropes, plastics, bones, even sod. I also have another in O1 and M2 with similar grinds.

A properly ground blade, with a 15-20 degree angle will cut anything you want it to and stay sharp longer.

Any angle will cut, the more acute generally better for longer not shorter, assuming the steel can take it, not all of them can.You need to adjust the angle to the steel.

As noted in the above the method Thom described doesn't work well for stainless, and is best done on very high tool steels, especially the HSS ones.

For the steels which are not as strong and tough you still grind flat to the stone, but then apply a small microbevel to apply the necessary strength, for most materials (not thick metals) this bevel is too small to see.

Now if you are chopping, not cutting, you need a heavier edge bevel, again how much depends on the steel, but generally most folding knives have edges which are thick enough for large chopping bowies.

A 15 degree edge for example is easily strong enough on even a decent steel to chop up caribou legs with no visible damage, this is obviously way overkill for a utility knife made to cut things.

When you move up to really strong and tough steels, it is just really under using the potentional of the steel.


-Cliff

 

[Bill DeShivs]

Cliff
That's a nice paring knife. The hollow grind is similar to a razor, so flat sharpening will work. Also, the blade is very thin. Thin blades, like razors can only get so dull. Most knives are not made this way, nor should they be. This is a specialty grind.
BTW- 1095 steel is the equivalent of most of the high carbon steel used in knives for the last century or so. It is a fine steel, and will cut about as well as any other-if properly heat treated.
I stand by my statement- knives should not be sharpened flat on a stone (unless specially designed for such). Any knife manufacturer will tell you this. Knives have been made for hundreds of years. They are refined pretty fully at this point. To think that anyone has recently discovered a revolutionary sharpening method is presumptious. Flat sharpening contributes little to sharpness, considering the wear and abuse on the blade. Of course, you can do it any way you like.
Bill

 

[Cliff Stamp]

I stand by my statement- knives should not be sharpened flat on a stone (unless specially designed for such).

That depends on what you want to do with it, if it is to cut things and your goal is to do this well for a long time, then this is what is required, as noted some of the lower end steels or steels with less than ideal heat treatments will require a microbevel, this however doesn't need to approach 20 degrees and can be done with just a hint of a arc on the edge stroke.

As for any manufacturer saying this isn't recommended, this is simply false. Lots of knives are sharpened without secondary bevels and run full grinds, many puukkos for example are sharpened in this manner and most convex ground knives run no secondary bevels and are sharpened full from spine to edge on the stone, many chisel ground knives are the same.

You can find these in both custom and production.

To think that anyone has recently discovered a revolutionary sharpening method is presumptious.

It isn't revolutionary, as Thom noted origionally it is very old. I heard it from a traditional maker from Malyasia who learned it from the guy who taught him who likely didn't invent it either.

Flat sharpening contributes little to sharpness ...

It contributes noting to sharpness, this is independent of angle and simply dependent on edge alignment and minimization of irregularity, what it does do is maximize cutting ability, edge lifetime, ease of handling of the knife and stability of the edge profile.

1095 is a decent steel, and when properly hardened lends itself well to a utility knife, it however can't stand with M2 which will outperform it several times to one, especially in corrosive enviroments.

-Cliff

 

[Bill DeShivs]

Cliff
Let me ask you a question-do you make knives? You may make some of the nicest knives in the world-I don't know.You may be a metallurgist. Again, I don't know.
The problem with the Internet is that anyone can set themselves up as an authority. If you tell people long enough they will believe it. Sort of like most people consider the guy behind the counter at a store an expert on what he is selling. If he happens to be selling toilet paper, I guess that makes him an expert on butt wiping!
I have seen a lot of knives in my life, and never have I seen it recommended by any maker or manufacturer to lay the blade flat when sharpening. Maybe I just am not upon current events. Perhaps you could direct me to an authority who agrees with you? I really hate to see you telling people to do this. If it were one of my knives I would be appalled. A nicely polished blade would be ruined.
Bill