Cutting test: 3 S30V knives

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Jun 8, 2005
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When I started this project tonight, I did not intend it to be a cutting test, but due to some surprising happenings, that's just what it became.

My 2nd story apartment window has a street light directly outside...consequently, it's day light 24/7 in here. So I bought a lot of this thick black cardboardesque stuff, with the difference being there's foam inbetween the two construction paperish sides. It's about a cm wide.

Obviously, it's to be taped to the window...the difficulty is that the window is arched and curved in places (and in big ways) so I had to stencil it out and then cut out the parts, then tape them to the window.

In retrospect, I should have used scissors, but I didn't expect this stuff to be nearly so tough.


Okay, to business: the three knives used were the S30V Dodo, S30V Para and S30V Blue Bump. They were all three not too extremely sharp, although the spydercos were noticeably sharper than the Bump (which is still on its factory sharpening). People who have read my Bump review might remember I was rather dissapointed in the factory sharpness...I haven't gotten around to sharpening it yet, but there are some surprisingly results.

The first trimming was with the Dodo...it seemed like the obvious choice, given its blade shape. It's never let me down. I sank the tip into the top of the line I drew on the foam/cardboard and pulled...and...nothing...it took a huge amount of force to drag it along the line. I then went to sawing with the reverse s part of the blade, which was still a hassle but somewhat more successful.

I finished that trimming and decided to try the Para. The Para outperformed the dodo significantly, but there was still a shockingly high amount of force necessary to cut through it...I sawed through it.

After that trimming was done, I decided to see if life would be easier with the Bump. It's worth noting again that the Bump isn't especially sharp yet (noticeably less sharp than the other knives here) and so I didn't expect much. The Bump excelled here, even if it is vastly outperformed in hair shaving and paper slicing. It could be dragged through with a little less resistance than the para, but back and forth slicing went through it like nothing...I reason that it must be the huge recurve at work.

The Bump was used for the rest of the cutting with good success.




Update: I cut up some leftover scrap with three different knives: the VG10 Spyderfly, the AUS8 M16 (50/50) and SAK Cybertool.

The Spyderfly did reasonably well as long as you were cutting in the area of the false edge...at the base, it stopped as soon as it hit the broad spine of the blade.

The M16 was surprising...it's a reasonably thin blade, nice polished/tini finish, I expected it to work great. Unfortunately, it did horribly on the test...bound up almost immediately.

The SAK performed by far the best, thanks most probably to its tiny width and highly polished finish (probably confirming Cliff's hypothesis). Next time I have to do something similar, I'll just use my SAK.
 
Interesting.

Perhaps the Bump had more "micro-serrations"?

Perhaps the thichness of the board had its affect, also.
 
I expect blade thickness, edge geometry and blade shape to explain this one...

Edge geometry I aint too smart on, but I have tried cutting stuff with different edges with very weird results, like this one. My benchmade 41MC never felt that sharp (D2), but would practically cut through cardboard on its own with on assistance from me.

The para has a surprisingly thick blade at the base and I think that may have caused a lot of resistance. The dodo has never slowed down cutting through anything...it's been a machine...I'm not sure how to explain that one.

A lot of people disagree with me, and a lot of them know a lot more than me, but in my real world experience, recurve blades vastly outslice my other ones...once it hits that bump on the blade, it drops the whole cut 2 cm automatically and you repeat.
 
I like recurves.

They make for better pull (and sometimes push - depending on how much curve there is) cutting.

I was also thinking the foam may of been grippy. I cut up (sawed, actually) a thermo-shipping box of similiar construction. Once the blade was so far in, that stuff would just "suck" onto the blade. That stuff was approximately an inch and a half thick, though.
 
I imagine it must be the foam inbetween myself...the black on the outside, as best I can tell, is just like construction paper...should be no sweat for an S30V spyderco.
 
Maybe try later with a med-grit stone giving a less "polished" edge to your Spydies? It's what I did to my Delica... and though I've traded away my Dodo - I'm curious... I would have thought it wouldn't hang up on anything (the tip is somewhat delicate though).
 
senoBDEC said:
... Dodo - I'm curious... I would have thought it wouldn't hang up on anything...

Foam insulation is really binding, locally Olfa knives are commonly used to cut it as it is too thick for carpenter/stanley knives, and the Olfa's zip through it readily. A thicker knife will cause the force to skyrocket and also make it break/fracture. Yu can also score it and crack it.

Generally you don't want to run more coarse edges because the force necessary to cut the material isn't an issue but the binding force on the sides. A high polish on a very thin blade works best. Difficult to cut with thick blades but much nicer to work with than the fibreglass insulation which is harder on the blades and on the user generally.

-Cliff
 
I used to carry a SAK when I used to work installing that, not for cutting, but for prying and general heavier work. The blades used for cutting that materials are only 0.020" thick at the spine, these are the "heavy duty" Olfa knives. You can make SAK's cut it ok if you take a file and rip off the primary edge so essentially it is fully flat ground right to the edge. It still binds more around the spine than the Olfa's, but it is a lot better than stock.

-Cliff
 
I recently moved and wound up with a bunch of cardboard boxes to be cut up in sizes that I could easily fit in trash bags. I didn't make any scientific, numerical comparisons, but I did use four different knives, and found different results from each. An S30V Native was used first and only for a short time. I have reworked the edge to be convexed, very thin, and somewhat polished. It was a big disappointment. I expected the type of hollow grind to cause some problems with binding, but I didn't expect it to be this severe. I only used it for a couple of boxes before it was put away. An Endura in VG-10 was next. It has about the same convex edge profile as the Native, with the same degree of polish. It cut somewhat better, due to the flat grind (I guess), but still produced more drag than I expected. A Case Trapper with carbon steel blades was next. At one time I had convexed the edges of both blades on it, but it was a little dull, so I made a few passes on a very fine diamond stone with both blades, and stropped them on loaded leather. It cut very well, much like I expected, but the size of the handle caused a good amount of hand fatiue. Lastly was a small utility knife I made of 3/32" thick 15N20. It has a 1 1/2" wide blade with a 2" cutting edge and is fully hard, with only a 300 degree temper. It is flat ground to the spine very thin and has a slight convex edge to sharpness. The same strop was used on it, as well. I fully expected it to cut the best and was pretty surprised to find that the Case did just as well, as far as force nedeed to make the cut. I did find that if I choked up on the blade and only used about the last 3/4", the force needed to cut was pretty much equal to the Case, but that grip was pretty uncomfortable.

I wound up using the utility knife the most and just dealt with the hand fatigue from the choked up grip, and I have concluded that full grinds that go all the way to the spine drag less than others (duh), and that thin blades outcut thicker ones in this type of cutting (duh, again). I was very well pleased with the wear resistance of the fully hard 15N20, though. I think it probably matches the S30V Native and the VG-10 Endura in edge holding, and it actually seems to chip less than either of these two, even at that extreme hardness and thin profile. The S30V seems to chip more than the VG-10 in normal use, strangely, but I don't have any tests to back up that observation.

Todd
 
Todd Robbins said:
I think it probably matches the S30V Native and the VG-10 Endura in edge holding, and it actually seems to chip less than either of these two, even at that extreme hardness and thin profile.

L6 has a torsional toughness maximum at a 275 F temper, 15n20 I would expect to be similar, so the materials data tends to support that result. Have any pictures of the knife?

-Cliff
 
Sorry, Cliff. I don't have any photos. I'm kind of technologically impaired and wouldn't know how to post one if I had a paid membership. I should catch up on that sort of thing, but I just haven't prioritized my time to do it yet. I'll describe it as best I can, though. It is 5" overall with a 2" warncliffe blade that is 1 1/2" wide. The stock was 3/32" thick, it is flat ground to the spine, and the edge is very thin. I gave it a convex edge with sandpaper and a mouse pad, stroking the edge into the paper with fairly light pressure and the blade laid as flat as possible on the paper, so the edge is very thin. The handle is rounded from the side, but it's got 1/4" black linen Micarta scales on it so it's fairly flat from the top. I made it because I needed a small utility knife at work on short notice, I had the materials on hand, and it was quick to make. I've been very pleased with it so far, though it is pretty limited in its scope of work. I've made a couple of other utility patterns so far out of 5/32" 440C that are a big improvement in comfort, stain resistance, and looks, but they won't hold an edge as well and won't cut with the ease of the first one.

Todd
 
You might want to try M2, it is available readily in the form of power hacksaw blades, it will be a large improvement over bandsaw steel in both edge retention and corrosion resistance.

-Cliff
 
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