Serrations prove useless--I'm grinding them off

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CountyRat said:
I own one serrated blade knife: a Spyderco Tenacious. I bought it for one purpose: to attach to a pocket on my personal flotation device (that's a "life jacket," matey!) for use at an aquatic camp I was going on with my son's Boy Scout Troop. Why? In case I needed to cut wet rope or webbing quickly in an emergency. PS: I also had a plain edge Rukus in a belt sheath for any other cutting that I might need to do. I carry that Rukus whenever I am camping. The serrated Tenacious is a great knife, but it lives in that PDF pocket, waiting for another boating trip.
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Jeff Clark said:
County Rat, Have you actually experimented with the wet rope and webbing? I carry a plain edge Spyderco Calypso Junior clipped to my shirt collar for situations like that. I think it would work better in most circumstances.
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what if that rope is large diameter? Try cutting through 1 inch diameter polypropylene rope with a plain edged knife and see how long it takes.

County Rat, I see that you are in Central Illinois. The rope you will most likely encounter in the water in central IL is not going to be 3/8 or 1/2" boating line. It is going to be large 1 1/2 to 2" diameter poly or nylon/poly scrap from one of the thousands of barges that ply the inland waterways. Even the single strands of rope like that are around 3/4" . Keep that serrated knife handy when you are in or around the water. It will eat through that stuff faster than any plain edge, no matter how sharp. It is no contest.

Serrated knives have their place and purpose. To say they are useless is a broad generalization. SOME serrations are useless, especially the ones ground on lower end knives for looks rather than function. I prefer a shallow, less-pointy serration and the serrations on Victorinox knives are one of my favorites. Every commercial fishing boat that I have seen have Victorinox serrated paring knives on them and I have used them for cutting rope, plastic, rubber hose, heavy tire rubber used as chafing gear, etc. and they outperform plain edge knives by miles.

There are a lot of factors involved in choosing a serrated knife. Style or pattern, depth, length of the points etc. all figure in to a serrated knife's functionability.

Serrated edges are no more difficult to sharpen than a plain edge with "the right tool for the job" I.E. a sharpmaker or other triangular stone system. I have sharpened serrated knives to shaving sharp on the sharpmaker and even repaired the edge on an Endura and a Harpy, both with VG-10 blades, with a sharpmaker.

Pete
 
I'm sure there are some freakish materials that serrated knives work better on, but I am discounting the ones that I have not had to cut in the last 60 years of my life. My primary point is that serrations don't work better in applications where I thought they might. For example they don't work better on polypropylene rope that I encounter which is under 3/4" in diameter. I may need a knife to cut a rock climbing rope, but not to cut a barge hawser.

Anyway I am primarily talking about utility for my city knife.
 
I have a normal SAK I carry with me all the time. Serrations have a purpose and on an EDC they are usefull as a 2nd blade/edge for cutting cord. My wife bought me a SAK with primary serrations and it is the only knife I have willingly destroyed in utter frustration. It seems to me an alternative for people who don't sharpen their knives regularly. Not much use unless there are some micro loaves of bread around. It butchers cloth, paper, soft veggies.
 
Pete1977 said:
County Rat, I see that you are in Central Illinois. The rope you will most likely encounter in the water in central IL is not going to be 3/8 or 1/2" boating line. . . . Serrated knives have their place and purpose. To say they are useless is a broad generalization.Pete
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Pete, I could not agree with you more. Serrated blades exist because they are the best tool for certain situations. I have never said they do not have valid uses, or that, in some situations, they are superior to PEs. As for my Central Illinois homeland, it does not matter because I never go boating here. We were camping in a Canadian camp and sailing small boats. The largest material I might possibly have needed to cut would have been a 1 1/2 inch PFD ("life jacket") strap, or a 3/8 inch polypro line. I needed a cheap serrated knife for this one trip. If I were a mariner, I would not have chosen the Tenacious, though it is a good knife. I would have invested more money in a better, larger knife specially designed for aquatic situations. And yes, it would have had a serrated blade because serrated blades are better than PE when one has to cut wet, heavy, rope or canvas, especially in a "the stuff has hit the fan!" situation.

As always, it is never about the knife; it is always about the user and what best adapts to his or her intended use. SE vs PE; neither is better. They are different designs with advantages and disadvantages in different situations.
 
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I have a SOG Pentagon, a SOG Paratool, each has a seperately designated serrated edge. Magic. The Paratool has a serrated blade that is simply excellent. But the SAK version is poor and illogical. Many blades are compromised by trying to put too many options on it, including a small section of serrations.
 
timcsaw said:
Serrations "rule" if you keep in mind that every sharp edge consists of serrations/"saw teeth" at the microscopic level.:D
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no, not really. Verhoeven has a paper with pics of edges from an SEM. Those finished with chromium oxide did not have teeth.
 
I guess, but I personally consider images from 600 to 3000x magnification powerful enough.
 
hardheart said:
I guess, but I personally consider images from 600 to 3000x magnification powerful enough.
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Yes, at those powers the "teeth" that do exist, are evidently not visable... They eventually would be if one used higher magnification levels (my point is, all edges consist of "serrations" at some level of magnification so essentially, every edge is serrated).:D:p

I like serrations (and so does everyone else whether they know it or not;):D).
 
Do you have any pics at a high enough magnification? I'd like to check them out, Verhoeven's paper seems to have the highest of the published papers I have. The next closest seems to be Takekoshi/Gotoh, but they only use 500x.
 
You're going to have to get to very high magnification with an SEM to see "serrations" with Verhoeven's 1/2 micron diameter edges!
 
Broos said:
You're going to have to get to very high magnification with an SEM to see "serrations" with Verhoeven's 1/2 micron diameter edges!
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Here are a couple of high magnification SEM images.

The first is a X50.000 shot of the pearlite region of a fractured hammer claw.

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This second one is a X10,000 of Iron Oxide.

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There is just no escaping the natural "serrations" inherent in the crystalline structure of metal.:D
 
hardheart said:
no, not really. Verhoeven has a paper with pics of edges from an SEM. Those finished with chromium oxide did not have teeth.
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Verhoeven et al's paper is instructive and valuable to anyone who wants to improve their understanding of blade sharpening, steeling, and honing procedures. However, the work is limited by the fact that the authors start with the assumption that a thin, straight, flat edge will cut best, without doing any experiments to determine if that assumption is true. Follow-up research is needed to determine whether blades without microscopic serrations actually do a better job cutting things that than blades with microserrations, a question Verhoeven et al never address. My hypothesis is that it would be a mixed bag, with flat, thin, straight edges doing better on some jobs, and blades with micro serrations doing better on others.

Anyone have a reference to research that addresses this?
 
If you have a problem cutting rope with a serrated knife, that means you're doing it the wrong way. The fact that you're talking about "sawing" through the rope is a further indication of that. It's all right though, noone is forcing you to buy serrated knives. :)

edit: This thread appears to be a lot older than I first realized, I apoloqize for the reanimation. I made the mistake of posting in a random thread from search results, sorry.
 
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hardheart said:
Do you have any pics at a high enough magnification? I'd like to check them out, Verhoeven's paper seems to have the highest of the published papers I have. The next closest seems to be Takekoshi/Gotoh, but they only use 500x.
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I have a number of images taken at 640 and 1600x (technically 400 and 1000x because the wavelength of light prohibits greater magnification than 1000x - so some of the increase is low quality digital enlargement, must go to SEM for higher). That said, any edge that fails to show teeth at 1000x (and there are plenty) effectively have no teeth - take a look at common objects at the same magnification and it becomes clear that any teeth too small to see aren't going to interact in a meaningful way with whatever you're cutting. I will add that it is difficult to get to that level of polish by hand - edges that look wonderfully polished by eye or even at 120-200x look a lot different at 640 or higher.

This is one at 1600x from a 1200 grit King - no real serrations, but some formations visible.
1095_1200k_1600.jpg


Here's another one at 1600x that shows even fewer formations
Martin_1600.jpg

this is what it looked like at 160x, by eye it looked nearly polished
Martin_160.jpg


This one is at 640x - scale at upper right is 7.7mu - consider a single blood cell is about the width of the scale. A single human hair is 30-50 mu and would take up about a third of the image area at the low end. This edge is hair whittling. If I'd added the same scale to the above 1600x pics, it would be about 3mu,a human hair would take up over half the image area.
CAT_640_Scale.jpg


FWIW I don't much care for serrations, but there are certainly formations on rougher edges that absolutely have an effect on cutting performance depending on what it is you're cutting. The formations have to be able to press into the target material and separate it somewhat, or IMHO there'll be no advantage. Not sure what other folks find, but for me, as near as I can figure, when the edge reaches the example of the hair whittling edge above, it starts to loose all drawing advantage - that is there's no real improvement in cutting with a drawing motion as opposed to a pressure cut. From that point on I'm pretty sure the formations, microserrations, whatever you want to call them become irrelevant unless you're cutting something with a microstructure small enough to interact with it - not sure what that would be. That said, there's sure to be formations present at any level of polish if you can get a close enough look until you're down to the crystalline structure - do they matter at that scale is a better question?

Here's one from an 800 grit King stone - very toothy, but not really serrated. The high points are pretty polished from stropping on newspaper and mighty acute - at a guess I'd say a micron or just under, the low spots are considerably thicker. This edge could easily shave your face, but then it would itch like mad for a couple of hours. Was amazed it could tree-top leg hair.

Mora_800K_640x_Cal-1.jpg


Serrations are a little different than coarse edge formations but not so much in how they work. I find I have to use less pressure and more movement with serrations and they work OK - they choke with too much pressure - more like a pruning saw, and a plain blade with a somewhat rougher edge might be comparable to a hack saw at the same scale.
Disclaimer - I'm not a materials engineer or professional hone-meister, all observations based on sloppy experiments with few or no controls.
 
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