How to maintain/sharpen carving knife?

O

Omega Leather Works

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Jun 13, 2007
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Hey guys. Just got a handmade carving knife. The edge has no bevel per se. It looks like a convex zero grind, and the blade is 1 3/4" long.

Here's a pic

IMAG0720_zps37e726be.jpg


These knives need to be razor sharp and this one certainly is! I want to keep it that way, but I'm not sure how without putting a primary bevel on it.
 
Strigamort said:
Hey guys. Just got a handmade carving knife. The edge has no bevel per se. It looks like a convex zero grind, and the blade is 1 3/4" long.
(...)

These knives need to be razor sharp and this one certainly is! I want to keep it that way, but I'm not sure how without putting a primary bevel on it.
Click to expand...

If it's a convex zero grind, these are really, really easy. I have a couple Opinels that I maintain in exactly the same condition. Just 'strop it' (edge-trailing) by laying the lower portion of the convex flush to some wet/dry sandpaper on a fairly firm but forgiving backing (like thin leather on a hard backing, or over a few sheets of stacked paper on a hard backing). To maintain it at/near the high polish shown, use high grit (1000/2000+), and then strop the blade on leather w/compound in the same manner, with the blade flush. If it needs a little more work, start lower in grit at anything in the 400-800 range, then follow with the higher grits and stropping, in the same manner. Laying the lower portion of the convexed blade flush to the sharpening/stropping media makes angle control as simple as can be. Just make sure the edge itself is making contact (lightly), and minimize pressure exerted, to prevent the sandpaper or strop from rolling over the apex.

As you get familiar with this technique, you might work on doing it on increasingly firmer backing, like thinner leather, harder wood, or a sheet or two of stacked paper over glass (this is how I like to do it), which will help keep the edge as crisp as possible.


David
 
I was looking at the web page for these knives, and the edges do look convex, though not as much for the blade as a whole (like Opinel). I'd still use sandpaper over a firm backing (the firmer the better), in a stropping fashion to maintain them. The convex is closer to the edge itself, so it's a bit rounder. The blade as a whole seems to be flat stock, maybe with a little taper towards the edge. Keeping the backing under the sandpaper as firm as possible will help to minimize any excessive rounding beyond that. If it were mine, I'd probably be using the sandpaper directly over glass or hardwood.


David
 
After holding a square edge to it it seems to be flat ground with slight convexing at the edge. Sorry about that! :o

David, I think your advice still applies. I have a thin leather strop with green compound. I'm thinking about using that. I've never had anything in zero edge, and I was worried about stropping it flat since the finish is perfect, but after a small amount of thought I'm not worried about it. If nothing else it'll add another dimension to my nutty quest for edge perfection.

Sorry about the pic. I took it right as I got it out of the box and half asleep. I'll try to get a better one up in a bit.

Thanks for your help guys, as always your advice is very much appreciated!
 
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Look like it has a full-convex grind. You may try using dry marker to put a few big X on the blade face (spine to edge), then scrape it flat on a piece of white paper, the worn mark might clue in what its actual grind profile.

David's suggestions are very good for wood working tools in general. But sound like you don't want to scratch the mirror look. So, it's good idea to strop using the finest compound on hardest backing. Could even try strop using Cr0 (0.5um) on a packing/scott tape, which is tape onto a glass surface. Always approach at the lowest angle possible (zero/lay-flat in this case).
 
i overlooked where you checked the blade with a straight edge :D. i sharpened about 700 woodcarving knives a while back for a member and he had me flat grind them all to get rid of the shoulder from where they were hollow ground instead of flat ground. i would put some tape just above the edge to protect the biggest part of the blade and then lightly strop it.
 
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Yeah it gives the appearance of being convex because there is a very slight convex at the edge and the top is rounded.

So I've been at it for a little while and I'm slightly concerned with the edge durability. If you watch Gene Messers youtube videos on ball in cage demo I'm making my cuts in a similar fashion, although his wood appears to be a bit softer than mine. Both are bass wood. In any case I am getting some slight edge rolling. Now I know that this is a thin edge, but I'm not being overly aggressive. Stropping looks to be setting the edge back up, but it rolls again. I can certainly work with it, but I thought 01 was tougher than this?
 
01 should be tougher than that for sure. you might want to try holding the spine up just a little when you strop it. it is possible that your edge is too thin.

if i get a chance when it warms up outside so i can set up my wet sander i would like to make you a carving knife from some of my 1075 and have you test it out.
 
Could be a wire-edge from over-stropped. Also becareful not to round the edge. My stretch cf zdp can easily get rounded and a wire-edge together from over stropping (and or excess pressure).
 
bluntcut said:
Could be a wire-edge from over-stropped. Also becareful not to round the edge. My stretch cf zdp can easily get rounded and a wire-edge together from over stropping (and or excess pressure).
Click to expand...

Nah it started rolling from new.

I'll take into consideration what you guys have said. I'll report my findings.

Richard, I replied to your pm. Your offer is intriguing. :)
 
Strigamort said:
Yeah it gives the appearance of being convex because there is a very slight convex at the edge and the top is rounded.

So I've been at it for a little while and I'm slightly concerned with the edge durability. If you watch Gene Messers youtube videos on ball in cage demo I'm making my cuts in a similar fashion, although his wood appears to be a bit softer than mine. Both are bass wood. In any case I am getting some slight edge rolling. Now I know that this is a thin edge, but I'm not being overly aggressive. Stropping looks to be setting the edge back up, but it rolls again. I can certainly work with it, but I thought 01 was tougher than this?
Click to expand...

That does seem strange, that the edge is rolling from cutting basswood. O1 should do better, assuming decent heat treat. Does the maker spec what the RC hardness is supposed to be for this knife? Even at 'typical' hardness for such tasks done with pocketknives (mid-50s or better, I'd at least hope), I'd think it should hold up better, unless the edge is actually much thinner than it looks in the pics.

If the edge keeps rolling, another thing to try might be a quick micro bevel. Just a couple or three light edge-leading passes per side on a ceramic hone at a slightly wider (more obtuse) angle. I'd be curious to know how it performs after doing that.


David
 
Obsessed with Edges said:
...
If the edge keeps rolling, another thing to try might be a quick micro bevel. Just a couple or three light edge-leading passes per side on a ceramic hone at a slightly wider (more obtuse) angle. I'd be curious to know how it performs after doing that.


David
Click to expand...
I would check the edge with a good magnifying glass or better still a jeweler's loupe to see what's really going on. If you are sure it is rolling or maybe just a persistant wire edge flopping from one side to another, then I would do what David suggests above.

If you are still not happy, contact Gil Drake about the warranty.
 
markksr said:
I would check the edge with a good magnifying glass or better still a jeweler's loupe to see what's really going on. If you are sure it is rolling or maybe just a persistant wire edge flopping from one side to another, then I would do what David suggests above.

If you are still not happy, contact Gil Drake about the warranty.
Click to expand...

I'm keeping my fingers crossed that it's only a flimsy wire edge doing this. Even so, I'm somewhat surprised that it'd be rolling back/forth so readily, instead of breaking off. I'm used to seeing that sort of ductility with softish and relatively low-carbon stainless steels (420HC and similar, at mid-50s RC), because the higher chromium tends to contribute to that. O1 does have a tiny bit of Cr in it (~ 0.5% or so), but I'd think it shouldn't be enough to matter here. In relatively simple carbon steel, I'd still expect wires & burrs to scrub off pretty quickly with stropping or under use. I don't have any O1 blades, but at least with the 1095 blades I've used, wires and burrs generally come off very easily. I'd think the RC hardness would have to get pretty low for them to hang on, otherwise.


David
 
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markksr said:
I would check the edge with a good magnifying glass or better still a jeweler's loupe to see what's really going on. If you are sure it is rolling or maybe just a persistant wire edge flopping from one side to another, then I would do what David suggests above.

If you are still not happy, contact Gil Drake about the warranty.
Click to expand...

I pulled out my cheap loupes. I'm still struggling to see what is actually going on here. Now it's looking like the edge might be getting waves in it and not rolling. I believe that would be down to a soft ht in any case.

I tried to take pics, but it's very hard with my phone. First is just phone, second is through the 10x loupe.

IMAG0729_zps4486f742.jpg


IMAG0730_zps445a8d07.jpg


It's easier to see in rl, but I did my best with these. :o
 
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