edge dulls quick - whats the solution?

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DavidL41

Joined
Oct 12, 2014
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I been using my knife for a while and when I drag the knife on surface like wood the edge dulls quick. Is this a sign that I sharpened wrong, too toothy of an edge or the edge is too thin I think its around 10- 15 degrees per side.
 
What is the knife, and blade steel?
What sharpening system do you use?
Will the blade shave and slice paper easily before you dull it?

I doubt that your edge is anywhere near 10 degrees per side.
 
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DavidL41 said:
I been using my knife for a while and when I drag the knife on surface like wood the edge dulls quick. Is this a sign that I sharpened wrong, too toothy of an edge or the edge is too thin I think its around 10- 15 degrees per side.
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If it happens all the time, you might be stopping short of a truly burr free edge. A smallish burr can cut for a while but will flip or roll easily on wood etc.

The edge angle may very well be too acute, there is a huge difference between 10 and 15 per side - 20 and 30 degrees inclusive. On most steel 30 will hold up, 20 will not. It is unlikely the edge finish is a major factor but is possible. For carving I have noticed a finer edge finish lasts longer than a rough one, though both tend to last long enough to be acceptable. My kitchen utility knives that see plenty of contact on the cutting board are done to approx 600 grit and stay sharp for a long time - cutting board sticky. If the wood contact is repetitious, as in you use a wood backer for cutting leather etc, the board itself might be contaminated with grit and that will kill and edge in very short order.
 
Something else to consider...

If you are raising a burr when you sharpen, but not completely removing that burr at each grit, then you might be breaking off the burr when using.
 
Please don't tell me I'm the only one who caught that the OP scrapes his knife on wood and seems surprised that it dulls the edge? I don't see the point in scraping wood with your knife edge unless you have a purpose in doing it.
 
He should be surprised if he makes a pass through wood and the edge goes dull. We'll need somemore information to be certain why. You can do a lot of carving with a knife of nearly any steel before it goes dull, assuming it was properly sharpened and the maker remembered to heat treat it. If he's really doing lateral scraping, that could account for it, but I doubt thats what he's talking about. He could just be worki g on really dirty timber, but it doesn't sound like that either.
 
I know, but the only thing I can imagine when he says scrape on wood is someone trying to use a 5 dollar gas station knife to saw a 2x4 in half.
 
He has not been on since his original post. I am curious what he has for a knife as well.
 
Noswad0208 said:
Please don't tell me I'm the only one who caught that the OP scrapes his knife on wood and seems surprised that it dulls the edge? I don't see the point in scraping wood with your knife edge unless you have a purpose in doing it.
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I'm not reading it this way. I'm of the impression he's talking about drawing the edge linearly through or over the wood, as if cutting or carving into it. If that's the case, could be any number of things happening, like a burr that's folding over and rounding the apex, edge geometry too thin, steel's heat treat too 'soft', wood much too dirty/abrasive, etc, or any combination of those things. Drawing a freshly-sharpened edge through wood is one method used to scrub burrs off, so that could be what he's attempting. Sometimes the burrs just fold over, instead of breaking off. If that's happening, it'd create the issue he's seeing (edge going immediately dull). A folded burr is likely the most common result; especially when seeing the edge go immediately dull after sharpening. Edge geometry too thin, or steel too soft to support thin geometry is likely the 2nd most common cause of such a symptom.

Decent cutlery steel with good heat treat shouldn't dull that quickly anyway, even in laterally 'scraping' the wood with the edge. Some woodworking tools are made for this purpose ('cabinet scrapers'); the edge is 'sharpened' (ground) to a heavy burr left intentionally on it, which is used to shave wood from the workpiece, for smoothing or shaping it. Those often aren't hardened above low-50s on the HRC scale (Veritas spec's theirs at 48-52 HRC), and they still hold up fairly well to the designed task.


David
 
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Sorry I forgot to check back in...

The knife is 154cm steel 60rc.

I think it could be that something to do with the burr folding over? I use a rough stone like the ones you find in home depot and use the fine side.
The steel may be too hard for the stone maybe. would that mean I need a another finer stone like a dmt extra fine to get rid of the burr better? I usually go straight from the stone which is sort of fine and go straight to green compound and it seems to remove the burr.

When I talk about dragging on wood I mean using it a wood cutting board to use a drag cutting motion on leather.
 
DavidL41 said:
Sorry I forgot to check back in...

The knife is 154cm steel 60rc.

I think it could be that something to do with the burr folding over? I use a rough stone like the ones you find in home depot and use the fine side.
The steel may be too hard for the stone maybe. would that mean I need a another finer stone like a dmt extra fine to get rid of the burr better? I usually go straight from the stone which is sort of fine and go straight to green compound and it seems to remove the burr.

When I talk about dragging on wood I mean using it a wood cutting board to use a drag cutting motion on leather.
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That reminds me of the 'sister steel' to 154CM, it's Japanese equivalent ATS-34 (same elemental makeup as 154CM). I do have a few blades in ATS-34 at similar hardness, and the burrs on those can be tenaciously tough to remove by simpler means like dragging over/through wood. The steel can be very ductile, even at this fairly high hardness, and if the burrs 'flip' at all, they'll often just bend back & forth without breaking off. ATS-34, VG-10 and sometimes 420HC will sometimes just laugh at burr-removal techniques that work on simpler steels, like cutting into wood. A good, firm strop with some AlOx compound, like white rouge, is what I 'go to' with steels like these (works for most others as well).

If the hardware-store stone is one of the older inexpensive AlOx (aluminum oxide) stones, those can sometimes create more burring issues than they fix. Cheaper stones in AlOx can easily glaze over with more wear-resistant steels (like 154CM), and they'll get very slow. Usually, the extra grinding pressure applied to 'speed it up' will create bigger burrs. Newer stones in the same price bracket are now sometimes found in silicon carbide abrasive (Norton's most current 'Economy' stone at Home Depot, for example), and it's not as bad in that regard; usually much better, in fact. I've been using two 'inexpensive' SiC hardware store stones, one is the 6" x 2" Norton Economy from HD, the other is a smaller (pocket-sized) but identical-makeup ACE Hardware stone; neither of them have exhibited any glazing issues, so the abrasive stays 'fresh' and cuts consistently. I just bought the larger 8" x 2" equivalent from ACE, for a third stone in this material (can you tell I like them? :D).

A better-quality stone than what you've got might be a better match for 154CM. Norton's higher-line Crystolon (silicon carbide) and India (aluminum oxide) stones should work, as would a good diamond hone, like DMT's Fine or EF, in particular. Those would be my first choice; the 'Fine' DMT could easily re-grind new bevels on 154CM, and can also leave a great working edge by itself. The EF would make a good finishing/refining hone, though re-bevelling could be somewhat slower on it, and overwork the hone.


David
 
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Another thought is that stropping with the fine Chromium Oxide off the fine side of a hardware store stone is not the best matchup, especially on that steel. Some black emery compound from Ryobi or Sears might make a much nicer edge for longevity sake. The finer abrasive of the CrO is likely overworking the apex and not keeping up on the cutting bevel - slight rounding of the edge that will lead to a more rapid drop-off in performance.

I hate to say it, but in my very humble opinion you might really be better served with a high carbon steel blade and a more aggressive compound applied to a hard backed strop, balsa, etc. Your application is that of a working knife and your maintenance scheme will need to be fairly robust. The higher carbide steels might hold an edge longer, but also take longer to sharpen and do not generally respond as well to hasty recovery methods as carbon steel, especially if worked to a fine edge.
 
I have to jump on and support the theory that your technique may need refinement. In my experience, and I have talked with Ankerson about this, 154cm can be a great steel. Certainly 60rc seems very reasonable. I might suggest a Spyderco Sharpmaker to start with. It's very predictable, and will give you a good baseline to start with. I use a Wicked Edge, but every once in a while, 5-10 passes on the grey Spyderco stones will really do wonders until I can sit down and "finish" an edge on my WE.

Heck, I have a Jeremy Robertson El Patron Wharnie that wasn't sharp upon arrival (bought used, no dig on Jeremy) and 10 passes on the Spyderco grey stones had it popping sharp. That is on 3V.

ETA: there are some very smart guys that have answered before me. All good info. I have read and learned a bunch right on this forum.
 
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Ok so let me try to understand. I should get a more aggressive type stone for this sort of steel like a norton or dmt and the type of steel I have or stainless in general is harder to sharpen but holds a slightly longer edge. This steel doesnt handle green compound/ chromium oxide because the steel doesnt sharpen well with it and rounds the edge as a result?

Can I keep stropping the blade on a carbon knife once I set the knife up or will it eventually round the edge?

If I was to buy a brand new knife in the future for leather working a white carbon steel blade thats has a thin edge like 30 deg inclusive would hold an edge for a long while before it needs to be re sharpened? Are there any benefits of going as low as 16 degree inclusive for leather working.There isn't too much stress on the knife and will be handling stretchy type leathers that needs the sharpest edge or else it will stretch it out.

Basically the above is my idea of what the best knife Is for my task, however I'm not that savvy and have as much knowledge on this matter.

In your opinion since the knife I have isn't as good as I thought it is, what specs would make the best knife for my application for PRECISION, SHARPNESS with the use of a ruler. This would really help me out.

1. blade length
2. type of carbon steel
3. Blade angle
4. type of grind (Scandi, hollow,convex ect) opinion on chisel grind vs double grind?
5. blade shape
6. Some one who makes this sort of knife or one thats in production.
 
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