440c and carbide tear out

D

davek14

Joined
May 30, 2009
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I've always used simpler sharpening equipment on my knives, which are usually simpler steels. I use emery cloth taped to metal plates and ceramic rods quite a bit.

I've picked up some "better" steels lately and some diamond rods and paste to handle the sharpening. Gotten much better edges on D2 and 440C. I still don't have the coarse diamond I would need for real re-profiling of blades though.

So, would coarse emery cloth do for reprofiling 440C without carbide tear out? Followed by prolly some finer emery then fine diamond (handheld) rods. Finishing with diamond paste on balsa.
 
davek14 said:
So, would coarse emery cloth do for reprofiling 440C without carbide tear out? Followed by prolly some finer emery then fine diamond (handheld) rods. Finishing with diamond paste on balsa.
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Hi,
What is carbide tearout or what do you understand it to be?
How big are carbides in 440c?
How big is "coarse" emery cloth?

If coarse is P40-P220 coarse or 425-68 microns coarse
And the primary carbies are 25 microns
and apex (tip of edge) is about 1 micron
...
i think tearout cannot be avoided, 1 micron thick of steel can't hold 25 micron thick of carbide
aside from that emory should work
 
The carbides in 440C are all chromium carbide. As such, I personally wouldn't worry about them tearing out, as they're relatively easy to grind and shape with any man-made abrasive of AlOx or SiC (or diamond, obviously). If your emery cloth is true to the definition of 'emery' (i.e., 'emery' is historically 'natural' aluminum oxide, but the term is often misapplied for SiC as well), it should be fine. I've personally favored SiC wet/dry paper over emery cloth for grinding 440C, as SiC cuts it much more cleanly. My own use of emery cloth leaves me with the impression the abrasive is more 'blocky' than SiC, and although hard enough, maybe not shaped so sharply as SiC or diamond, and therefore doesn't cut as cleanly for the sake of the edge's crispness. It takes metal off easily enough, but leaves the edge in a lot rougher shape afterward (very heavy burring, for example).

For all it's chromium carbides, 440C is relatively ductile at the hardness typically seen in such blades (mid-50s to 60-ish HRC), and I think generally less prone to anything chipping, or breaking out of carbides at the edge, per se. 440C is pretty easy to shape and refine at the edge with anything beyond simple Arkansas stones, without worrying about any such issues as carbide tear-out. And for polishing 440C, any decent aluminum oxide compounds like white rouge, Mother's Mag, Flitz or Simichrome can work really well with it. Diamond paste can work too, but isn't really necessary, to handle the chromium carbides in 440C or D2 and other similar steels.

My own impression of grinding, refining and polishing 440C is based on results I'd obtained on one of Buck's older 440C blades (Buck 112 'two dot' model), which were reputed to be fairly hard to sharpen at one time (back in '70s/'80s especially). I'd tried, years ago, to thin & rebevel that knife with Arkansas stones; it just laughed at them. I gave that up and shelved everything on that knife for many years. Fast-forwarding to more recent days, I retried the same task a few years ago, with wet/dry SiC paper (ate the steel for breakfast), following that with polishing on a hard-backed denim strop with aluminum oxide compound (white rouge, or maybe Simichrome). The results blew me away, as compared to the impression left from the Arkansas stones. Easy, easy all the way.


David
 
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dave, that topic was written about much here and I never accepted it. Still, I know where your coming from. On the cheap get sheets of wet/ dry SiC sand paper at 100 grit and that will reprofile 440C. The steels you mention are not as easy to reprofile as kitchen knife steels nor do they take as much time as the vanadium steels. You've stepped up to some better steels. I think you'll enjoy working with them. If the edge was left thick you'll have to grind at it. Good luck, DM
 
Obsessed with Edges said:
The carbides in 440C are all chromium carbide. As such, I personally wouldn't worry about them tearing out, as they're relatively easy to grind and shape with any man-made abrasive of AlOx or SiC (or diamond, obviously). If your emery cloth is true to the definition of 'emery' (i.e., 'emery' is historically 'natural' aluminum oxide, but the term is often misapplied for SiC as well), it should be fine. I've personally favored SiC wet/dry paper over emery cloth for grinding 440C, as SiC cuts it much more cleanly. My own use of emery cloth leaves me with the impression the abrasive is more 'blocky' than SiC, and although hard enough, maybe not shaped so sharply as SiC or diamond, and therefore doesn't cut as cleanly for the sake of the edge's crispness. It takes metal off easily enough, but leaves the edge in a lot rougher shape afterward (very heavy burring, for example).

For all it's chromium carbides, 440C is relatively ductile at the hardness typically seen in such blades (mid-50s to 60-ish HRC), and I think generally less prone to anything chipping, or breaking out of carbides at the edge, per se. 440C is pretty easy to shape and refine at the edge with anything beyond simple Arkansas stones, without worrying about any such issues as carbide tear-out. And for polishing 440C, any decent aluminum oxide compounds like white rouge, Mother's Mag, Flitz or Simichrome can work really well with it. Diamond paste can work too, but isn't really necessary, to handle the chromium carbides in 440C or D2 and other similar steels.

My own impression of grinding, refining and polishing 440C is based on results I'd obtained on one of Buck's older 440C blades (Buck 112 'two dot' model), which were reputed to be fairly hard to sharpen at one time (back in '70s/'80s especially). I'd tried, years ago, to thin & rebevel that knife with Arkansas stones; it just laughed at them. I gave that up and shelved everything on that knife for many years. Fast-forwarding to more recent days, I retried the same task a few years ago, with wet/dry SiC paper (ate the steel for breakfast), following that with polishing on a hard-backed denim strop with aluminum oxide compound (white rouge, or maybe Simichrome). The results blew me away, as compared to the impression left from the Arkansas stones. Easy, easy all the way.


David
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Yup. The only time you'd have to worry about carbide tearout with 400C would be if you're using natural stones. Aluminum oxide, silicon carbide, and (obviously) diamond and CBN are all significantly harder than chromium carbides.
 
Per David Martin, some silicon carbide wet/dry will tackle those steels no problem. 120 grit will eat 154cm or 440 readily, and these papers lend themselves to easy progressions. A combination stone from your local ACE will do fine as well.

Natural stones even can do a good job sharpening but will have a tough time if the edge needs thinning.

Personally I'd stay away from emory cloth for anything knife related aside from cosmetic surface work. The cloth will have more give than a wet/dry sheet over a stone or steel plate, glass etc. Do not use open coat woodworking sandpaper, and even some of the "multi-purpose" sandpapers are not so effective on hardened steel - silicon carbide wet/dry gives good consistent results.

Use an eraser or synthetic wine cork to clean the paper often and use a light touch, or if using a combination stone use with mineral oil or dunk in a water bath frequently.

440c is still one of my favorite knife steels.
 
Thank you all for your timely and informative answers. I hope I am not a pest as I slowly improve my sharpening "on a budget". I am a machinist and have access to slightly used emery cloth for free. I've used it to sharpen for years and it works very well on carbon steel, 12c27, 8cr13mov and the like.

I had problems with D2 though. It would take a long time to sharpen and go to "working sharp" really quickly, albeit staying that sharp for a while.

After reading about carbide tear out here on BF I asked a few questions in this subforum about D2. Now, after sharpening with handheld diamond rods and stropping on only diamond paste and balsa. I get acceptably sharp edges which last. If I sharpen on emery or do much more than a light touch up on a ceramic rod though, I'm back to square one. The diamond seems to be required.

I still like simpler, but still good steels on my work knives. I don't need anything special to strop and I have easy access to stones, emery, etc. The "better" steels are for home carry.

So, am I hearing that 440C is a little more forgiving than D2? I have a few knives which I want to re-profile, thinning the edge quite a bit. I'll probably try some pretty coarse (80), then medium (120) emery, then fine diamond rods. The emery is "AO", aluminum oxide I guess.

Thanks again for your help.
 
With D2 a lot of it has to do with the fairly large carbide size. There's a reason the common saying about D2 is "takes a poor edge and holds it all day". That's emphatically not a condemnation of the steel, but rather mirroring your observation that it's not going to easily achieve the same high level of sharpness that other finer-grained steels will, but it does hold that working edge for a good long while.

Aluminum oxide and silicon carbide are both harder than chromium carbide, which is the sort you'll find in 440C, so no issue there.
 
davek14 said:
Thank you all for your timely and informative answers. I hope I am not a pest as I slowly improve my sharpening "on a budget". I am a machinist and have access to slightly used emery cloth for free. I've used it to sharpen for years and it works very well on carbon steel, 12c27, 8cr13mov and the like.

I had problems with D2 though. It would take a long time to sharpen and go to "working sharp" really quickly, albeit staying that sharp for a while.

After reading about carbide tear out here on BF I asked a few questions in this subforum about D2. Now, after sharpening with handheld diamond rods and stropping on only diamond paste and balsa. I get acceptably sharp edges which last. If I sharpen on emery or do much more than a light touch up on a ceramic rod though, I'm back to square one. The diamond seems to be required.

I still like simpler, but still good steels on my work knives. I don't need anything special to strop and I have easy access to stones, emery, etc. The "better" steels are for home carry.

So, am I hearing that 440C is a little more forgiving than D2? I have a few knives which I want to re-profile, thinning the edge quite a bit. I'll probably try some pretty coarse (80), then medium (120) emery, then fine diamond rods. The emery is "AO", aluminum oxide I guess.

Thanks again for your help.
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440C is a lot easier to sharpen with aluminum oxide abrasives (in particular) than D2. Technically, they both have the same types of carbides (primarily), but D2 likely has more of them because D2 also has a much higher carbon content (D2 @ ~1.5% carbon vs. 440C @ ~1% carbon), to combine with it's chromium and make the carbides, and they're very large as well, in the non-CPM versions of D2. D2 also has about 1% vanadium content, which might be just enough to influence it's wear resistance as well. 440C doesn't contain much, if any, vanadium to influence wear resistance in it. The only troubles I've ever had, in sharpening 440C, is with Arkansas stones as I mentioned earlier. Otherwise, I've felt 440C to be barely more difficult than steels like 440A or similar, on anything other than Arkansas stones.

My favorite edges on D2 are all pretty highly finished, up to ~ 2000-grit or so. Although I don't agree with this assumption in the first place, the likely reason some think D2 won't take or hold a finer edge is because it doesn't respond to refinement very well with lesser-quality abrasives, like cheaper AlOx stones, for example; I'd also include emery cloth in that group. This is exactly the same type of limitation to sharpening any highly wear-resistant steel: if the abrasives aren't adequate to cut the carbides cleanly, results will be poor. At fine, very fine and mirror-finish levels, D2 is much more responsive to diamond in particular, as it will cut those large carbides much more cleanly without causing tear-out. Once the apex is shaped and refined with a higher quality abrasive (SiC & diamond work best with it), it's much easier to maintain a higher finish. I've often used a very hard strop of wood or hard-backed denim on D2, with either diamond paste (on the wood) or an aluminum oxide paste or compound (white rouge, Flitz, Simichrome, etc). I still prefer to use a Fine or EF diamond hone on D2, to fully restore the apex's crispness, if it seems to need it after a while.


David
 
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Emery is a mixture of Aluminum Oxide and Iron Oxide. Iron Oxide is not a very hard abrasive. 440C is the high Carbon version of 440. In addition to its high level of Chrome Carbides, it has a more wear resistant matrix owing to its higher HRC. So harder steels and softer abrasives don't get along well.
 
I've noticed that the D2 edge morphs into a less sharp working edge rather quickly. I sharpen it on a Norton fine SiC stone (240 grit)and it doesn't hold that level as long as a blade of 440C. Yes, it (D2) has vanadium and little (.2-.4 )more carbon but 440C has 5.5-6% more chromium in it's mix. And those carbides are hard as well. Which is what gives 440C that type edge. I don't own a diamond stone beyond fine. So, to tinker further with it I'd have to take it to my Spyderco fine & ultra fine and get OCD over it. Which I won't do. So, I don't experience the edge you mention. I'll grant, there could be a difference noticed in it when taking a D2 edge that fine. Just my experience with it. DM
 
So, I'm of course hearing that emery cloth will work fine on 440C. Still, I'm a bit obtuse.

The 440C carbides are of the same hardness as the D2 (chromium carbides), and I'm hearing that emery will shape them. Personal experience shows me that the harder sharpening medium works galaxies better in D2. So the fact that the carbides are smaller makes it easier to shape them without tear out?

I'm not trying to just keep the thread up top, I promise.;). As usual the answers are patient and super informative. Now that Christmas is over I'm just going to have to quit talking and get my hands in this.

Merry (a few hours late) Christmas, merry gentlemen.
 
davek14 said:
So, I'm of course hearing that emery cloth will work fine on 440C. Still, I'm a bit obtuse.

The 440C carbides are of the same hardness as the D2 (chromium carbides), and I'm hearing that emery will shape them. Personal experience shows me that the harder sharpening medium works galaxies better in D2. So the fact that the carbides are smaller makes it easier to shape them without tear out?

I'm not trying to just keep the thread up top, I promise.;). As usual the answers are patient and super informative. Now that Christmas is over I'm just going to have to quit talking and get my hands in this.

Merry (a few hours late) Christmas, merry gentlemen.
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The abrasive ('emery', a.k.a. aluminum oxide) is hard enough to abrade chromium carbides, and certainly enough to hog off steel. It's just that the particular grade of aluminum oxide (in emery cloth) isn't really the best for the job, in sharpening either 440C or D2. Even 'fine' emery cloth is still pretty crude, coarse stuff. So far as I know, emery cloth doesn't come in grades fine enough to compare to the refinement capabilities of better grades of AlOx in sharpening tasks. AlOx comes in a huge variety of qualities, and some varieties will cut much more cleanly than others, due to differences in shape (huge differences), consistency of grit size, friability, toughness, etc.

The easiest way to see how it'll work is to try it, and compare it to results seen from other AlOx-based sharpening media, i.e., polishing-grade AlOx (polishing tapes, etc.), waterstones, AlOx oilstones actually made for sharpening knives, etc. In my own experience sharpening both 440C and D2, there's an obvious difference between the two, with 440C being much, much easier to grind and refine. I'll still assert it's likely due to the much higher carbon content in D2 (and maybe just enough vanadium as well), which contributes directly to carbide formation, versus 440C, in which the chromium content is higher than in D2, but it gets split between carbide formation and corrosion resistance in that steel, with a larger portion of it not being bound up in carbides (due to less available carbon in 440C, than in D2).

Carbon is what makes the difference in wear resistance, all other variables being equal. To prove it, compare grinding and refining 440A vs 440C, the only difference being the carbon content (440C's carbon is about double that of 440A), with everything else being the same, including chromium content. 440A was designed more for ease of sharpening and higher corrosion resistance, whereas the priority in 440C was more toward wear resistance, with somewhat lesser corrosion resistance. The carbon content is literally the only factor making that difference in those two steels.


David
 
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