Demonstrating Edge Geometry on Cardboard (940 vs. Delica 4 vs. Military)

Рет қаралды 2,573

3 жыл бұрын

Lots of unflattering shots in this one so be prepared! Thin spines and full flat grinds (FFG) have often been toted as the hallmark of a slicey knife. I contend that for tasks that don't cause wedging (most EDC knife tasks) the angle and thickness behind the edge far outweigh the aforementioned grind geometry.
For 2 layers of cardboard, the military was worst but the others were similar. For 4 layers, the 940 pulled ahead a little. For 6 layers, the 940 was the clear winner despite having a thicker spine, worse steel and a worse grind for slicing when compared to the delica.
Steel performance was good on all blades throughout the testing. The CPM-20CV @ 59HRc didn't hold a perfect apex but did have low/moderate bite still. The CTS-204P @ 61HRc held a nice apex and after cleaning did have moderate bite. The K390 @ 65HRc held the crispest apex (feels almost same as starting) and had moderate/good bite left. All stropped back to easily hair shaving with 4um CBN on leather.
Benchmade 9401-1501:
Spine: 0.115"
Edge: 15dps w/20dps micro @ 0.008" BTE (Carter Cutlery regrind. Factory was 17dps @ 0.027"BTE)
Steel: CPM-20CV @ 59HRc
Sharpening: Spyderco medium then fine ceramics, 4um CBN on leather.
Spyderco Delica 4:
Spine: 0.090"
Edge: 15dps @ 0.015" BTE
Steel: K390 @ 65HRc
Sharpening: 400F Venev resin bonded diamond waterstone, 4um CBN on leather.
Spyderco Military:
Spine: 0.145"
Edge: 17dps @ 0.024" BTE
Steel: CTS-204P @ 61HRc
Sharpening: King Neo 800, 4um CBN on leather, 1um diamond on wood.
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Пікірлер: 24

@turing2376 3 жыл бұрын

Interesting demonstration of edge geometry. Pondering about what exactly might have been going on with the 940 seemingly maintaining more aggression. So many factors that i can imagine, both in actual edge and also in means of testing that could be at play.

@EngineersPerspective701 3 жыл бұрын

It was actually just all gummed up from tape residue. I put it in the video description because I didn't want to edit the video or anything. Can't figure out how to annotate them either!? After cleaning up the blades I said 940:low/moderate bite with non-deal apex. Milie: moderate bite with nice apex. K390 moderate/good bite with best apex. All stropped back pretty well on 4um CBN after.

@turing2376 3 жыл бұрын

@@EngineersPerspective701 ahh, I missed that. Well, less of a mystery then I guess.

@EngineersPerspective701 3 жыл бұрын

@@turing2376 I was confused/surprised in the testing too. I really need to learn how to put a note in the video to correct mistakes or point things out!

@EngineersPerspective701 3 жыл бұрын

@@turing2376 Here is an update. The military and para 3 seems to hold the "fine bite" better than the 940 does. But the 940 breaks down into a coarser/toothier working edge. This was a mystery but when I reread Larrin's S45VN article I noticed that the carbide volume decreases with higher austenizing temperature that are required for higher hardness. It's my guess that the 940 has a higher carbide volume overall because less of the carbide was dissolved due to lower austenizing temp. That in turn gives a toothier working edge. It's more complicated that what's above because the temper makes a difference too but I think that is the culprit at the moment.

@turing2376 3 жыл бұрын

@@EngineersPerspective701 hmm, then if only the military had the reground 940 geometry that would sound pretty good to me. I'll take the knife that I can get the edge closest to the performance of a kitchen knife while still holding up to a little bit harder use than kitchen use. BTW, thanks for the recommendation about going back to the DMT coarse. Did a little sharpening experiment of my own. The other day I sharpened relatively thin edge spyderco MBS-26 petty, spyderco sage s30v and native s35vn. Sharpened all with coarse DMT then directly to first paint stirrer loaded with both 4 and 0.5 micron diamond emulsion on same stick, then followed by stick with 1 micron emulsion. MBS came out hair shaving, hair whitelling, cleaning cutting free hanging paper towel and came up easily/quickly. The other two I felt ok about, a little worse performance on all measures basically (not quite as good bite or quite as smooth cutting on any of the media). Not quite hair whitelling, maybe catching a little from what I can remember now, doing other tasks ok. Also, with the PM steel knives much more care had to be taken, redo of the course stone on at least one of them I think. Took longer. So I am gleaning that the simpler steel and narrow bevel of the petty made it much easier to get consistent flat bevel for progression to strops and then better performance. So, there you go, 3 knives sharpened, got it all figured out...🤣😂

@ReapersEDC Жыл бұрын

K390 all day. Even when it feels dull it still cuts endlessly. Keep in mind the delica 4 is lightweight also.

@EngineersPerspective701 Жыл бұрын

Amen to that!

@adanma17 3 жыл бұрын

Would be interesting if spyderco made a full convex grind for testing geometry.

@EngineersPerspective701 3 жыл бұрын

Certainly would. You could probably manage it by hand if you really wanted to. I'd recommend any of their seki laminated blades to speed up the grinding.

@adanma17 3 жыл бұрын

@@EngineersPerspective701bark river has some slicey blades because of their grind which makes me curious as to other companies if they had zero grind too.

@EngineersPerspective701 3 жыл бұрын

@@adanma17 I'd love to see that more as well! Spyderco did it on the Lil' Nilakka I believe but the ATS-34 was wayyy to soft to hold it I heard.

@John..18 2 жыл бұрын

I have a convexed polished edge, on my "beater" Delica, (VG10) and it's an absolute demon, for cutting up cardboard boxes,, !! It's so good, I'm going to put the same geometry, on my new Endura,,, imho, VG10 is great for maintaining, with a strop, before you need to sharpen it "properly".. . Just my two cents,,,

@EngineersPerspective701 2 жыл бұрын

Sweet! Hand convexed? VG10 comes up quick and very sharp. Agreed that it’s a great steel to strop back. Trouble for me is it doesn’t take to the type of edge I’ve really grown to appreciate on the higher carbide steels. Definitely good to go though!