The edge doesn't last on the knives that I sharpen.

S

Squashfan

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Jun 6, 2012
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Well, here I am again. Humbly asking for assistance from the masters. I have noticed that when I sharpen with my diamond lansky the knife the edge doesn't last. I have always attributed this, first, to the blade steel (420HC, 13C28N, and Victorinox mystery) and second to my finishing hone. The finishing hone is a lansky ceramic stick. I now have the 1,000 and 2,000 Lansky ceramic hones as well as a plain leather strop. While the knives are getting sharper, they still aren't staying sharp. Ever my Queen Country Cousin in D2 has the same problem. I sharpened the Queen on Monday. I have used it to cut a couple plastic straps, 3 short cuts in very thin cardboard, 2 cuts of paper and a very little arm hair shaving. I checked the Queen for sharpness this morning and it had regressed to barely shaving sharp. When I first sharpened it the hair would pop off my arm, literally. What am I doing wrong?!

Edit: I just read Magnanimous G's post. I am not removing the burr but I don't know what to do. I have gone all the way up to the 2K stone and there is still a burr.
 
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If I were betting, most of the shaving sharpness may be coming from a wire edge or burr, which is weakened steel and will fold/erode away with more typical cutting tasks. Edge angles may also be a little bit wide (obtuse), which makes the loss of the wire 'shaving edge' all the more apparent. When the wire goes away, the relatively wide-angled apex will feel that much more blunt. Keeping the edge angle to 30° inclusive or less can make a big difference in how the edge performs, even after the shaving sharpness diminishes a little bit. And the narrower geometry of the 30° edge is much, much easier to restore to shaving sharpness on just a strop, perhaps with some compound (green, diamond). Making a 40° or wider edge shave is more challenging, and must be done with near perfection.

Could also be rounding the edge geometry somewhat on the ceramic stick (it's real easy to do, if angle control isn't near-perfect). And ceramics can also leave a significant burr/wire, which will do exactly what you've described (shave/cut for a short time, then fail).

You might focus on achieving shaving sharpness on the diamond Lansky (guided sharpener?) alone, and set the ceramic stick aside for now. It's possible many of your troubles (burrs/wires/rounded edges) may be coming from that. Assuming the Lansky diamond sharpener is guided, it should be the most capable of getting the edge geometry right, so long as the edge gets fully apexed. Going freehand to a ceramic stick afterwards is likely taking some of the precision out of the geometry.


David
 
It is the guided system and the 1K and 2K ceramic are guided as well. The edge angle is 20° per side. What I am doing is apexing and burring the edge on the medium diamond. Then I flip the burn once per side.
Example as if I had an apexed edge: One pass with the medium diamond creates burr. One pass other side with medium to flip the burr. One pass on the medium burr with a fine diamond. One pass to flip the burr with the fine. So on and etc. But even after I use the 2K super sapphire the burr is still there.
 
Squashfan said:
It is the guided system and the 1K and 2K ceramic are guided as well. The edge angle is 20° per side. What I am doing is apexing and burring the edge on the medium diamond. Then I flip the burn once per side.
Example as if I had an apexed edge: One pass with the medium diamond creates burr. One pass other side with medium to flip the burr. One pass on the medium burr with a fine diamond. One pass to flip the burr with the fine. So on and etc. But even after I use the 2K super sapphire the burr is still there.
Click to expand...

Focus on minimizing the burr using the diamond hones only (in the guide), before going to the ceramics (1000/sapphire). And I'd also recommend going even lighter with pressure; should be feather-light with the fine diamond. Heavy pressure just creates more burrs. There should be minimal burr on the edge when starting with the 1000 ceramic hone, and it should very gently abrade most of it away (whatever burr's there should be whisper-thin and should remove easily). Again, keep pressure feather-light. If there's still a noticeable burr after the finest finishing hone (sapphire), I'm sure this is where most of your troubles are coming from. I'm assuming the ceramic stick is being used in an attempt to clean up the burr, but it's probably also rounding/blunting the apex as well. Whatever burr is still there, is likely what you're getting the shaving sharpness from. And when that's eroded away during use, the relatively round or blunt apex is left.

I'd still recommend setting the ceramic stick aside (skip it), and go straight to the strop after the guided Lansky sequence. In fact, it may be a good idea to focus on perfecting the edge on the guided setup, and do some test-cutting with it for a while (even before stropping). The less you have to do freehand to clean up the burr, the easier the finishing step (stropping) will become. I think that'll do more to protect the good geometry of the edge, which is where real cutting performance will come from.


David
 
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Squashfan said:
It is the guided system and the 1K and 2K ceramic are guided as well. The edge angle is 20° per side. What I am doing is apexing and burring the edge on the medium diamond. Then I flip the burn once per side.
Example as if I had an apexed edge: One pass with the medium diamond creates burr. One pass other side with medium to flip the burr. One pass on the medium burr with a fine diamond. One pass to flip the burr with the fine. So on and etc. But even after I use the 2K super sapphire the burr is still there.
Click to expand...

The 20 degree per side is giving you a 40 degree inclusive angle. I would use the 17 degree setting to get closer to a 30 degree inclusive angle. Like OWE stated above, use much lighter pressure and the burr will abrade away. Try to get rid of it as much as you can with the first stone, and then progress to the other stones with very light pressure. Just try to cover/change the previous scratch pattern as you work your way through the stones. Light pressure is the key. Think about polishing the edge instead of grinding it away. Check for a burr or missed areas after each stone. Success is yours, just keep practicing.

Blessings,

Omar
 
With a burr that fine, couldn't you just lightly cut a cork or soft wood and the burr should come off? Right?
 
Sharpnessis said:
With a burr that fine, couldn't you just lightly cut a cork or soft wood and the burr should come off? Right?
Click to expand...

Sometimes they come off like that, and sometimes not. Very ductile steels sometimes don't like to let go of the burr, and some very gentle abrasion is usually the easier way to get rid of them. VG-10 and ATS-34 are a couple that can be downright stubborn, and cutting into wood, cork, leather, etc. usually won't faze them. 420HC at slightly lower hardness can behave in a similar manner.


David
 
I believe that a jewelers loop is in order. It should allow you to see what is happening to your edge when you sharpen.
I'm not sure that I've ever had this probelm, though I've read about it. When I sharpen a knife I will start with a coarse stone (generally) and use very light pressure. I will only move up to a finer stone when I can feel a bur on one side of the blade.
It could very well be that your edge has a micro-bevel and you need to re-profile completely before you can sharpen properly. Micro-bevels are cheating anyway. :p
 
Chris Pierce said:
I'm not sure that I've ever had this probelm, though I've read about it. When I sharpen a knife I will start with a coarse stone (generally) and use very light pressure. I will only move up to a finer stone when I can feel a bur on one side of the blade.
Click to expand...
I do a check for the burr before I go to the finer stone. What I was taught was that sharpening was the process of creating and then straitening the burr with finer grits.
If I understand what the forumites are saying, I should eliminate the burr BEFORE I move to the finer grits.

I shouldn't be creating a microbevel. I start with 20 degrees and work the scratch pattern down until I have a burr on one side. Then I do the same on the other until the burr flips from side to side with ease.
 
There are differing views on this. Personally, I remove the burr after every stone, even if starting with the 150 grit Naniwa Omura, it just doesn't have to be perfect. The finishing stone is where the burr removal has to be spot-on.
 
Thanks for all the help. I had a bad shock last night when I started reading the replies. This was completely different from anything I had read about sharpening. I will have to try this with a knife.

Oh, before I forget, when I sharpened the Queen it never touched the Lansky rod. It was guided system only.
 
Squashfan said:
Thanks for all the help. I had a bad shock last night when I started reading the replies. This was completely different from anything I had read about sharpening. I will have to try this with a knife.

Oh, before I forget, when I sharpened the Queen it never touched the Lansky rod. It was guided system only.
Click to expand...

I'll cut you some slack on the Queen. ;)

It's a 'special beast' with the D2 (I assume) blade, and that steel demands more patience in getting an edge fully apexed, even on diamond. It'll also not finish quite as 'toothy' as something like 420HC on the same abrasive, because the steel is so much harder and more wear-resistant. The abrasive won't dig as deeply, so the scratches will be finer. That puts a premium on making sure the edge gets completely apexed, and you'll also see a bigger benefit to going to a shallower angle (30° or less) with this steel.


David
 
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