BK24, is D2 that much harder to sharpen than 1095?

If it is a good heat treat, then it should be quite hard. Not really hard to sharpen with diamonds but the steel will be a lot harder than 1095.
 
I haven't found D2 to be harder to maintain the edge than other good steels with good HT. It takes a little longer, which means that I have to focus on what I'm doing a bit more consistently, but it isn't any harder as far as needing a different technique or kit.

I'm a daily knife user, but my cutting at this stage of life is very consistent and has been for a long time. I cut stuff in the warehouse (zip ties, very little cardboard, light computer cabling, packaging) and I cut bags, stems and other house & yard materials. Nothing heavy-duty or high pressure in what I cut. I've had D2 from BM, BHK, Keith Murr, and Spyderco (PM version). I use a Sharpmaker and a few strops. Occasionally, I'll use a fine Spyderco benchstone. I "touch up" a lot, though, so I don't spend much time having to do real sharpening.
 
D2 takes considerably longer, if all other variables are equal, to remove the same given amount of steel with the same tools or methods. 1095 literally has no hard carbides at all (chromium-, vanadium-, tungsten-carbides), so the hardness of the iron/carbon matrix steel is the only limitation. That's determined by the spec'd RC hardness for the blade, which usually won't account for the carbides at all, if present. D2, on the other hand, has an abundance of hard chromium carbides, which are much harder than the matrix steel (iron/carbon), and will not abrade nearly as easily. The difference between the two steels will be more easily noticed, if using somewhat softer/older sharpening media, like Arkansas stones or some relatively low-quality aluminum oxide stones. Trying to re-bevel with very small hones (like a Lansky guided system, and it's 4" x 1/2" hones, for example) will really reveal how much more work is needed with D2. Larger bench hones can speed things up considerably.

My Schrade USA 8OT stockman in 1095 was heat-treated by the mfr to ~60 RC or so, considered pretty 'hard' by most standards. The complete lack of chromium or vanadium carbides (70s/80s on the RC scale, respectively) means it's still a breeze to sharpen up or even re-bevel with most modern abrasives, like aluminum oxide, silicon carbide or diamond. I have a similarly-sized Queen stockman in D2, which goes much, much slower in re-bevelling tasks; at least until something like diamond is used to re-bevel it. Once re-bevelled and with good geometry at the edge, D2 is pretty easy to maintain with AlOx, SiC or diamond.

For stropping, green compound (chromium oxide) or white (aluminum oxide) works great for 1095. SiC and diamond can work also, but they're almost overkill for 1095; very easy to over-polish with either of them, if not careful. For D2, the green can sometimes be pretty slow, but AlOx, SiC or diamond compounds can make it really sing.


David
 
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I have a BK11 and not too long ago picked up a BK24. There is little difference when sharpening on wet/dry or a silicon carbide stone. I shaved a few degrees off the factory bevel and sharpened up my BK24 in about 20 minutes on my Washboard with 320 and 600 grit sandpaper.

The biggest difference comes when finishing - I find the D2 favors a rougher edge overall while the 1095 takes better to a finer edge. I did take the D2 to a pretty fine edge initially, treetopping leg hair, but after using it for a few took it back down to 600 grit and no stropping. I keep all my 1095 blades at a fairly high polish.
 
See the Traditional forum, for comparisons of 'ease of sharpening' between the two. A lot of fans of Schrade/GEC (1095) and Queen (D2) knives there, and the posts reflect the differences pretty clearly; especially when re-bevelling the thick(ish) factory edge grinds that often come on both brands (at least the GECs and Queens). The non-CPM version of D2 has chromium carbides that are much larger (sometimes huge, up to 20-50µ across, and big enough to see by naked eye, if the steel is acid-etched or darkly-patinated), so sharpening the Queens is impacted by that, especially in the finishing stages.

The thing that impressed me with D2 is, it'll take equally well to virtually any edge finish, and hold it a long time. I've tended to favor a higher finish on it, to levels at or above 1000+ or so, though it takes more time to really fine-tune it there. Once there, it really holds up well and is maintained easily on hard-backed strops in particular; I like white AlOx or diamond for this, in the ~1-5µ range.


David
 
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Obsessed with Edges said:
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D2 takes considerably longer, if all other variables are equal, to remove the same given amount of steel with the same tools or methods. 1095 literally has no hard carbides at all (chromium-, vanadium-, tungsten-carbides), so the hardness of the iron/carbon matrix steel is the only limitation. That's determined by the spec'd RC hardness for the blade, which usually won't account for the carbides at all, if present. D2, on the other hand, has an abundance of hard chromium carbides, which are much harder than the matrix steel (iron/carbon), and will not abrade nearly as easily...
Click to expand...

A little clarification on the bolded statement above. Yes, it's true that 1095 doesn't has any: VC, WC, CrC and a few others type such as MoC, NbC, etc... But it has plenty of iron-carbide/cementite. Fe3C (and depend on ht, form variance of smaller cementite). Cementite hardness is roughly around 74RC +- a few points. Which is a lot softer than common sharpening abrasives. 1095 in pure carbide molecular count, it has more carbide than 1084 (obviously); W2; O1; (other based on carbon % excess of 0.55-.6) and almost the same count as 52100.

D2 carbide (V, Cr, Mo) clumping/segregation into large structure 10-100um which can lead to sharpening difficulty. Well heat treated D2 mean = fine grain + fine carbide + uniformly fine matrix microstructure + no(or hardly any) retained austenite + no(or little) Cr23C6 + no embrittlet martensite/matrix ... :eek:
 
I can't speak to other manufacturers, but KaBar's D2 as used in my BK24 was no trouble whatsoever to work with - almost a let down as I was ready for some grinding.

The carbides in my example are quite large, possibly in the 20-50u range. Was able to work the edge fine with very little difficulty using AlumOx, SiC compound on paper, and also with diamond paste and diamond lapping film, though the SiC seemed to give somewhat better results than the AlumOx, the diamond was little different than the SIC until I switched to lapping film.

Ultimately, (and maybe due to the large carbide size) I decided its edge retention and cutting characteristics in general when left at a moderate finish level were much better than when done to a finer polish.

Really, this mirrors a lot of what I notice with higher carbide steels - they work better for me if I use the carbides as mechanical cutting features rather than as wear resistant pieces of a finer edge, and when applying a bright finish to the aggregate-like matrix of these steels, lapping film seems to do a much better job than stropping with paste or compound, even on very hard backing.
 
I'd bet the 'cementite' carbides aren't quite so hard (70s RC), or their size isn't significant enough to be an issue anyway. Were it the case, even the 'old school' Arkansas stones may have trouble sharpening it (and that was never an issue with 1095, so far as I know). This is why I stated there won't be any carbides influencing difficulty of sharpening 1095 with today's methods/materials. Mid-70s RC is in the same hardness range as (or perhaps harder than) chromium carbides.

Crucible has listed chromium carbides at 66-68 HRC, Moly/Tungsten carbides at 72-77, and Vanadium carbides at 82-84, here: http://www.crucibleservice.com/eselector/general/generalpart1.html .

Here's a link to another page, with Knoop hardness values for many materials, including Cementite (iron carbide) at 1025 Knoop and chromium carbide at 1735 (70% harder than Cementite, by this measure). See the 'Hardness of Materials' chart lower down on this page:
http://www.tedpella.com/Material-Sciences_html/Abrasive_Grit_Grading_Systems.htm


David
 
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Obsessed with Edges said:
I'd bet the 'cementite' carbides aren't quite so hard (70s RC), or their size isn't significant to be an issue anyway. Were it the case, even the 'old school' Arkansas stones may have trouble sharpening it (and that was never an issue with 1095, so far as I know). This is why I stated there won't be any carbides influencing difficulty of sharpening 1095 with today's methods/materials. Mid-70s RC is in the same hardness range as (or perhaps harder than) chromium carbides.

Crucible has listed chromium carbides at 66-68 HRC, Moly/Tungsten carbides at 72-77, and Vanadium carbides at 82-84, here: http://www.crucibleservice.com/eselector/general/generalpart1.html .

Here's a link to another page, with Knoop hardness values for many materials, including Cementite (iron carbide) at 1025 Knoop and chromium carbide at 1735 (70% harder than Cementite, by this measure). See the 'Hardness of Materials' chart lower down on this page:
http://www.tedpella.com/Material-Sciences_html/Abrasive_Grit_Grading_Systems.htm


David
Click to expand...

I agree, precipitated cementite in 1095 are small (sub 50nm) and softer than abrasive, to have any negative affect in sharpening. Thanks for the link. Cementite in cast-iron is most common and has the lowest hardness. I think, precipitated cementite is harder, after that epsilon/eta cementite would be even harder. Hence which cementite does this chart refers to? keep in mind most test tool are not really directly test carbide hardness because the probe/indenter is too large to test individual carbide (at clump/cluster level not molecular). I am sure particle collider can pin point hardness at super high accuracy :D

http://www.tribology-abc.com/calculators/hardness.htm
http://www.labtesting.com/wp-content/uploads/2012/08/chart-hardness-c.pdf
 
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in easier terms ,,D2 takes longer too sharpen yes, longer = more work? harder ? to some people ,yes.
 
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