A push cut?

  • Thread starter Thread starter db
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Yeah, I've also gotten different results with the same edge depending on how much of a chop, or press the cut is, and or how much flex , or floppy the paper is. The paper test is very technique dependent.
 
Phone books are even more difficult than newpaper, and certain catalogs - I think Campmor, but could be wrong - are even thinner. My best is around 3.5 inches with newspaper, and yes, it flops around, the knife has to **really** be sharp to be able to start a push cut in those conditions. Holding things taut is cheating.

I think it's worth noting that unless I'm whittling soft wood, those extreme push cut edges don't last very long, but the cutting ability lasts for quite a while due to geometry. If that makes sense.
 
hardheart said:
does everyone move the blade that fast?
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No. In threads where I've discussed the technique I use, e.g.

http://www.bladeforums.com/forums/showthread.php?t=424085

http://www.bladeforums.com/forums/showthread.php?t=433156

the edge of the blade is gently placed perpendicular to the edge of the paper, and pressure slowly applied until either it cuts, or the paper starts to bend/fold. I begin at a distance where I feel fairly certain a push cut won't be possible, then gradually work my way closer to the point of hold, about 1/10th of an inch at a time.

I can't say that Dan's videos don't demonstrate a push cut of sorts, but the fact that he uses a chopping motion and isn't cutting perpendicularly to the paper will of course allow the paper to be cut much further from point of hold.

I have a hell of a time getting past 2" when putting the blade against the paper and literally pushing. I got a very clean cut at close to 6" with that chopping like action, starting the motion about 3" above the paper (zdp caly).
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Push cutting newsprint has improved my sharpening skills dramatically, with certain blades I can push cut at over 4" on newsprint (compare the numbers I was getting in the threads linked to above with those in my infamous JYD2 review. For me the "secret" to achieving this kind of sharpness with a very fine, polished edge (coarse edges at very low angles can show impressive push cutting on paper as well, BTW) was learning to finish sharpen with the very lightest of pressure on fine ceramic Sharpmaker or CrockSticks. I don't strop, and in fact feel hand stropping only risks degrading an edge of this caliber ... however I believe using a system like the EdgePro with the fine polishing tape, and again the lightest of pressure, should be able to exceed what I can do by hand.
 
sodak said:
I think it's worth noting that unless I'm whittling soft wood, those extreme push cut edges don't last very long, but the cutting ability lasts for quite a while due to geometry. If that makes sense.
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I know what you're saying, and 8-9 months ago I would have agreed that that pretty much applies without any real equivocation. However this gets back into the issue of using extremely light pressure when applying the final edge, and in fact being moderate with the use of pressure throughout the whole sharpening process.

When I started experimenting with this, it really surprised me in a way. I mean, here I was applying a fine microbevel on a blade using this feather-like pressure, as though the steel were ultra fragile, and the result was not only finer, sharper edges, but edges that hold up immensely better under normal and even heavy use. The conclusion seems almost inescapable, flexion of metal when sharpening -- especially when working that fine, micron-thin final edge -- has to be minimized as much as possible in order to get a lasting edge.

The other factor of course is the inherent edge stability of the steel. The Sandvik stainlesses, or a simple carbon steel at decent hardness, totally outclass a lot of the cutlery that I, and I imagine most of us, have used over the years when it comes to quality, fine edges with good retention. With other steels, especially the high carbide content stainlesses, keen edges just don't hold up well, assuming you can even get one.

Or so it seems to me. :)
 
Chopping is very different than pushing, the two should not be exchanged, the mechanics are very different.

-Cliff
 
I am a novice working hard to become an amateur!:D

If anyone ever tells me that a push cut isn't possible, I get out my Cold Steel Survival-Rescue Knife (SRK) which is HUGE, and THICK! I spent many hours re-profiling it to convex with sandpaper and a mouse pad, and sharpening and stropping it. Now, it will push cut newsprint a full inch away from the fingers.

Would I like for it to be even sharper? Heck yes!:cool: But a big ol' honkin' survival knife like the SRK that will push cut at all is just incredible to me. Especially when a novice like me sharpened it!:D

Sure, it takes some work, especially for a novice, but it can be done, and the personal satisfaction I got from doing it was incredible!:p

Now, ALL of my knives will push cut!:thumbup:

(With many thanks for a lot of excellent advice that I got from Cliff Stamp here on this forum!)
 
Great job Ben! It's fun when you get it, isn't it? An inch on newsprint is very good, you should be happy! A lot of people look at my really big survival knives, and when I show them how sharp they are, they can't believe that a big knife can be that sharp. But "bigness" has nothing to do with it, as we both know.

If you really want to impress people with a test (that really isn't that hard), hold a piece of typing paper vertical, and just after you let it go, slice it in the air from top to bottom. Wows the snot out of people....

(I can hear all the guys running out into their garage right now... :D )
 
I was just at a party where a guy pulled out his GIN 1 Spyderco Native for some cutting, so of course I have to show him my Endura Wave. After a little talking on sharpness my wife pulls out a couple pieces of hair (I didn't even ask her to do this, she just did it. You've got to love a wife who does this AND buys me a sharpening stone for Fathers day) so I can whittle some hair for the crowd. That really impressed the crowd, as they had never seen that before. I threw in a little tree topping demonstration for fun. But when it comes to newsprint I measure as Dog of War describes, a deliberate cut straight down into the paper. As Sodak said phone book pages are tougher to do than newsprint, but I find them more consistent for measuring push cutting performance when checking your sharpness. I have to try the typing paper test that Sodak described, sounds like another crown pleaser.

Mike
 
Just for fun. I put a Shapton Pro 1000 grit finish on a knife of mine. This is a pretty coarse finish, more coarse than the Spyderco med. hone. I was able to press/push cut news print right around 4 inches from my hold. It also sliced up cardboard like a hot knife cutting butter. It's a little coarser than I like but it was fun to cut with. I'm rethinking real coarse edges.
 
what's the difference between distances on newsprint and phonebooks? I can get 2-2.5" on phone book pages, can a guess be hazarded as to what that would be for one of you on newsprint? All my newsprint is leftover filler from shipping, or papers from three years ago that have been sitting in a corner (USA Today & Financial Times, whatever quality paper they use). I think the humidity (S. Louisiana) and being stuffed in a box makes it weaker, but it's hard to tell.
 
Hardheart, I’m guessing because I believe the paper test is so Technique dependent that it is probably not good to try and relate one persons results to another’s. Your 2.5 could very easily be another’s 1.5 or 3.5 using the same knife and piece of paper. Then just think of the difference in paper quality from different places. Also how far of a cut into the paper qualifies as a pass, cut in two, half way down the paper, or just a little about the with of the edge bevel?
 
Well, if anyone uses just the height of the edge bevel, I'll have to re-evaluate my numbers. I can get a bite pretty far out. It would be nice to get something somewhat standard out of this. If there's too much variation in the test itself, then the reported numbers become useless.
 
hardheart said:
what's the difference between distances on newsprint and phonebooks? I can get 2-2.5" on phone book pages, can a guess be hazarded as to what that would be for one of you on newsprint? All my newsprint is leftover filler from shipping, or papers from three years ago that have been sitting in a corner (USA Today & Financial Times, whatever quality paper they use). I think the humidity (S. Louisiana) and being stuffed in a box makes it weaker, but it's hard to tell.
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Hi, hardheart. This got me curious, so I tested some Dex "yellow pages" paper against the newspaper newsprint I've been using for months. Freshly sharpened EKA 12C27 blade pushcuts the Dex paper at 4.2", the newsprint at 4.1". I really thought the phonebook paper would be more difficult to cut because it's thinner than the newsprint -- they mic out at .0023" and .0028" respectively -- but not the case.

db said:
Hardheart, I’m guessing because I believe the paper test is so Technique dependent that it is probably not good to try and relate one persons results to another’s. Your 2.5 could very easily be another’s 1.5 or 3.5 using the same knife and piece of paper. Then just think of the difference in paper quality from different places. Also how far of a cut into the paper qualifies as a pass, cut in two, half way down the paper, or just a little about the with of the edge bevel?
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Agree, db. For me consistency is the overiding concern when testing sharpness with newsprint, so my technique has evolved accordingly. One thing that I find very important to consistency is to have a clean, freshly-cut edge on the paper; much better results if the paper is cut to size with scissors rather than a knife. I size all my paper test "media" to 5 inches of length, and so that I'm cutting perpendicular to the direction the paper wants to tear cleanly (if that makes sense.) Width of the paper I've found isn't so important, between 2"-3" wide gives the same results.

It came up before here on BFC, can't find the discussion, but something some have noted is that with a really fine edge, a push cut into newsprint will start, go in effortlessly maybe a tenth of an inch or so, and then the paper wants to bend or fold. I'm pretty sure this is due to wedging, and it's usually this kind of cut that I report so long as they are repeatable. Many times you'll also see where an edge will inconsistently make tiny little nicks in the paper, no more than a couple hundredths deep; maybe you'll get one way out from point of hold, but you really won't get a significant cut again until you move in maybe another three tenths or half inch. I don't count nicks like these, IMO they're just flukes, maybe weak points in the paper.
 
hmm, I'll shoot for 2-3mm cuts. I was going for about an inch before, which is really enough to slice through the full sheet once you get it started. I'll also start working with smaller squares of paper.
 
hardheart said:
what's the difference between distances on newsprint and phonebooks? I can get 2-2.5" on phone book pages, can a guess be hazarded as to what that would be for one of you on newsprint? All my newsprint is leftover filler from shipping, or papers from three years ago that have been sitting in a corner (USA Today & Financial Times, whatever quality paper they use). I think the humidity (S. Louisiana) and being stuffed in a box makes it weaker, but it's hard to tell.
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As others have noted, it's very technique dependent. 3 inches on newsprint (for me) translates into 2 inches into a phonebook page. YMMV. Mine are all slow cuts, and I also live in a dry climate.

Gunmike1, you gotta try this as a party trick. Nothing says "Good Morning" than a nice big 10 inch bowie *cleanly* slicing a piece of paper in half while it floats in the air! I usually use my larger khukuris, just for fun. Seeing the wide eyes will just crack you up! Of course, your guests might end up standing a little farther from you the rest of the night... :D

If you guys want another test that isn't too hard but is fun, lay a newspaper down on a counter, and with a good sharp knife, push cut into the "flat" of the paper, and basically fillet the newsprint off of it, without going all the way through the paper. It's really not that hard, but it also amazes people who aren't used to sharp knives.
 
db said:
Just for fun. I put a Shapton Pro 1000 grit finish on a knife of mine. This is a pretty coarse finish, more coarse than the Spyderco med. hone. I was able to press/push cut news print right around 4 inches from my hold. It also sliced up cardboard like a hot knife cutting butter. It's a little coarser than I like but it was fun to cut with. I'm rethinking real coarse edges.
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That's impressive. I'd like to hear more when you've done some more testing with cardboard.
 
All my cardboard is currently shredded; the recycling guys better take it. LOL the 1000 edge also did some gardening and worked very well cutting things like string line a dirty root or two, and packaging. All of witch were pretty much more of a slice than a push cut.
 
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