Sharpening a convex edge

V

Virg

Joined
Jul 26, 2000
Messages
47
So I got my new Fallkniven S-1 today (Brian @ discountknives.com was fast!), and I want to maintain that factory edge. I read in the sharpening FAQ's that convex edges are difficult to maintain w/out a belt grinder (!) because of the curvature. However, the instructions on the Fallkniven box sounded pretty conventional to me. What's the best way to keep this baby sharp?


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V.
 
The best way to keep it sharp Virg, is not to cut anything! lol just kidding you!

I find that the best way to sharpen is the Gatco way, and I'm telling you... I get my knives razor sharp on this one. For me there is no other. Here is a link to where you can read about it, and also buy it... <a href="http://www.knifecenter.com/knifecenter/timberline/gatstix.html">Click Here For Gatco</a>

Now there are many others, and you will have to find what works for you, but this one is a fine sharpener, and I highly recommend it.

GOOD LUCK!

us_marine_corps_md_clr.gif


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BC... For those who fought for it, Freedom has a flavor the protected will never know... Semper Fi

[This message has been edited by narruc1 (edited 08-08-2000).]
 
Virg, I believe that the best way to keep a sharp edge on a good factory knife like the one you describe is to follow their instructions. However, I have been making knives for a few years and like the grind that you describe very much. I use it exclusively because I believe that a well executed convex grind is probably the best all around grind that you can have. There are grinds that are better suited for food preparation but would be less desirable in a working knife. I have discovered that the best method for sharpening is still a flat stone and plenty of practice. Don't ever let the knife get so dull that it requires the use of a coarse stone. My favorite is the Japanese water stone and after that my second favorite is a good old arkansas stone. If you are not proficient with a flat stone yet I would recommend that you practice on a knife that you would not worry about marring the finish on. By the way it always takes time to do a good job sharpening a blade in this manner. Don't get frustrated just because the process isn't instantaneous. By the way a belt grinder is not the best way to maintain an edge on the knife, it is just the quickest way to put one on. Knife makers use a belt grinder to put on a final bevel. this is fine. But to maintain a knife this way, if it is going to be used regularly, is to shorten its usable life span. This is true of the convex grind as well. Some makers may have the skill to do it this way for you and not take off too much steel, but these are people who have been grinding blades for years.
 
Geez, I hope I don't get arrested for this. Here is a post by Marble's Jason Stewart he made on that "other knife forum."

"It is extremely easy to retouch a convex edge. And, a convex edge does drastically out perform a flat, or especially hollow ground, blade.

You can use a medium and fine Arkansas stone to restore the edge. It takes a bit of practice, but once you get the hang of it, it is quite easy. All you're going to have to do is to use a "stropping" motion as a barber would on a piece of leather.

I always tell people to lay the blade flat on the stone and turn the spine of the blade upward until you feel a slight "tug" from friction on the stone. Strop it from choil to tip once or twice on each side, on each stone. Start with the medium grit stone.

The best way to ultimately finish the blade is to use a good leather strop or even your blue jeans for one or two more strokes. This usually refines the blade to an ultimate edge.

Ususally, those who are introduced to knives with convex edge geometry swear buy them and don't use much else after that. Try one of our knives and you'll see."

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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
I've got a Smith's Tri-stone setup right now, but want larger stones. How are the setups from RazorEdge systems? I don't know if those stones are natural or not; I assume they're synthetic.
Would stropping on a regular strop help maintain the edge, or is it just to polish once resharpened?

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V.
 
Keeping a convex edge on a flat benchstone requires you to pull the knife back and rotate it upwards at the same time to match the bevel curvature. It can be done, obviously, but it takes a fair amount of skill to do it. I have no doubt Jason can do this quite well considering his experience, but for someone who has not, it is going to be a very frustrating experience. It is far easier to use sandpaper on a soft backing as the bevel will be matched automatically.

Using a loaded strop will prolong the life of the edge of you knife. Using an unloaded strop will do the same but it will just help with alignment and for many of the stronger steels, commonly the very hard ones, an unloaded stop doesn't make much of a difference for me once blunting sets in. A smooth steel I find makes a bigger differece.

-Cliff
 
Originally posted by Cliff Stamp:
It is far easier to use sandpaper on a soft backing as the bevel will be matched automatically.
-Cliff
Click to expand...

Makes good sense to me.

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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
Yep, I think Cliff nailed it for we without slack belt grinders.

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rdangerer@home.com
 
Thanks, guys. Okay, I'm on the search for strop paste and sandpaper . . . what kind of grit are we talking about here?! Does anyone know anything about the "Handi-hones" from RazorEdge?? They look like they would serve for this as well. I guess I'm just anxious about using sandpaper; it seems to . . . brutal!
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V.
 
virg, I think they mean very fine wet/dry sandpaper. The black stuff. You can get grits up to 2000 fairly readily. Don't use 200 grit wood sandpaper.
biggrin.gif


Paracelsus
 
Virg, There is nothing wrong with using sandpaper. But if you have the time and the patience, learn how to use the stones that you have. Don't deprive yourself of the experience and the skill that you would develop using them properly just because you found a shortcut. The stones may be harder to use initially than the sandpaper but later on they will allow you to have better control of the sharpening process. Go ahead and use the sandpaper until you feel proficent in polishing your blade with the stones. That way you have a choice as to how to maintain your knife later on.
 
Virg, sandpaper abrasives are either AO, SiC or diamond grit, this is the same thing that many hones are made out of. I usually start off very low like around 220 SiC and work up to 600 and then finish on a loaded strop, just a couple of strokes. You can go much finer of course as there are very fine polishing sheets.

As for what kinds, I have tried all kinds, brands etc. . What I have found is that the really cheap sandpaper, like 12 sheets for a buck, while working well on woods and soft metals is not aggressive enough to bite into the harder more abrasion resistant steels in high end knife blades. It doesn't harm them to try, the knife just glides over the sandpaper.

You can usually find sandpaper for polishing metal which has a higher quality backing which resists tears etc., and a more aggressive grit like SiC or Diamond. These abrasives are hard enough to cut even the Vanadium carbides in the really wear resistant knife steels.

-Cliff
 
Thanks. I'm definitely going to try the sandpaper technique, but I'm intrigued by James point about learning to use the stone. I assume that this would be the stropping method that Hoodoo outlined, and not a 'std' slicing action?
 
I have seen it done both ways, I currently don't have the skill to do it well yet but practice off and on. I use it like a strop, stroking backwards and gently rolling the blade up on the pull stroke.

-Cliff
 
Virg, one more thing that I wanted to add is that regardless of what method that you use you should always finish with a strop. I will never sharpen a knife without finishing on a strop. I have never loaded a strop with any kind of rouge but I have some and am going to try it. The strop by itself makes quite a difference. Cliff has done some great reviews on CPM10V and convinced me to buy a length of it with which to make a knife. I made my knife with a convex edge and did the final shaping and polishing with two japanese water stones, and I of course stropped the edge. The first stone was 800 grit and then the final stone was 1200 grit. One point that I should make is that if you use the stones to sharpen a convex edge, it will probably not look like it does before you start. It will not be a smooth, even looking finish. If this doesn't bother you then good, but it is normal. You can't make something look machined if it is finished by hand. If the way it looks bothers you you can smooth the finish using the sandpaper that Cliff mentioned. Personally I don't particularly like or dislike the machine finished look. I do happen to prefer a good hand rubbed (sanded) finish.
 
James,
What sort of rouge did you get? I looked on the 'net and found some, but there was little info to distinguish between the colors offered, leaving me w/no idea about grit or whether it was a polish or just conditioner.
Good point about the look of the knife; it's now perfectly smooth down the very edge. Whether it's sandpaper or stone, I'm not likely to resharpen it w/out some visible indication that I've done so. I'm not eager for my blade to get scratched up, but I don't think that's what you mean.
Let me know what you think about your strop w/the rouge. Thanks

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V.
 
I see you have been getting a lot of advise, and I am offering you a quote from Jason Stewart of the Marbles knive co. Personally I purchased a $40.00 six inch Delta bench grinder and dedicated it just for this job.

"You most likely will get the best results, however, by using a stitched muslin wheel and then a loose wheel, both made of cotton.
On the stitched wheel, use a black greasy compound (about 600 grit) that you can obtain most likely from the same place you're getting your white compound. Lay the blade against the wheel at a slight angle (12 to 14 dgs.) and apply firm pressure, starting at the choil and working your way to the tip. One or two passes on each side should do it. COOL THE BLADE with water.

Now, use "knifemakers green" compound, also easily available through Koval or Brownell's, on the loose wheel. Be careful, these are grabby wheels . One or two passes on each side should work. Now you're done. By the way, you can probably substitute the white compound you have for the green.

Don't hurt yourself ."


 
Virg, The surface of the blade may end up with a slight patchy appearance. With practice you should be able to develop the skill to keep this down to acceptable limits. The way to do this is when the edge of the blade is about as sharp as you want it, start passing the blade over the stone from the edge straight back to the spine. If there are flats on your knife be careful not to scuff the point at which the bevel meets the flat area. By the way do not sharpen your knife by rubbing the stone against the blade. Always have the stone on a flat solid surface. Then holding the knife firmly in both hands pass the blade over the stone. This method will give you excellent control over your work, thus reducing frustration and fatigue. Also whether you use water or oil to lubricate the stone make certain that its surface is saturated. I started using oil but I now prefer water. Once you put oil on a stone you won't be able to use water on it ever again so make certain that this is what you want to do. Oh yeah, don't forget, any accidental scratches and scuffs that you might put on the convex surface will eventually disapper with normal maintenance as they get polished away with your stone. This is not so with a flat or hollow ground blade.
 
James :

By the way do not sharpen your knife by rubbing the stone against the blade. Always have the stone on a flat solid surface. Then holding the knife firmly in both hands pass the blade over the stone.
Click to expand...

That is interesting, I have also heard the opposite, that it is easier if the blade is fixed. I have been trying it that way using a small hone and can now get decent results on sharpness. I will have to try the other way as you suggest.

-Cliff
 
I have noticed that if one or the other is firmly placed so that one only has to concentrate on either the knife or the stone that consistent results are alot easier. However, from personal experience I have also notice that a larger stone also helps to give consistent result. I happen to believe that consistency is the most important aspect of good sharpening, more so than speed or grind angle. I figure that it is easier to swipe a blade (whether it is small or large) over a large stone than to move a large stone over the blade. Also, if you happen to use water (which I prefer)then having the stone stationary lends itself to keeping the stone saturated on the surface. The japanese water stones that I use are about two inches wide and eight inches long. They are 800 grit and 1200 grit. These stones are somewhat cumbersome and would be difficult hold.When using a fine grit stone like either of the ones that I have, I have found that a long stroke gives superior results. The best way to understand all of this is through experience. Cliff, if you could find a large, fine grit japanese style water stone and try this yourelf I believe that you would end up swearing by it, especially if you followed it up with a strop at the end. I started with smaller arkensas stones and oil myself. I still like them but I will not go back while I have a Japanese water stone with me. Though I have never secured a knife and sharpened it with the stone in my hand It sounds like a very good method of getting a good consistent stroke with good results, but I think that if you try this other method that you may be surprised at the consistency and the results.
 
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