What can serrations do that plain edge can't?

"I also maintain, that with the exception of carving
(whittling), scraping, chopping and shaving, that a
sharp Spyderco serrated knife will do anything that
a sharp plain edge knife will do. For those things, a
serrated edge is next to useless."

I had a car like that once. It ran okay except for on highways, and on country roads, and on city streets.

-Cougar Allen :{)
 
See the latest issue of Scientific American, where a guy experiments with different serration morphologies to determine which is more efficient at cutting meat and tendon.

It is in the T. rex section. Now THERE was an animal which was never without a knife!

Walt
 
Thanks for the heads up Walt. Which month is it? My local store is quirky in what they have.

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"A knifeless man is a lifeless man"
-Nordic proverb


 
Serrations can stay usably sharp longer without sharpening than a plain blade can.

Serrations can saw wood better than a plain blade can.

Nylon rope, nylon webbing, plastic tie straps, zip ties, etc... a sharp(-ened) plain blade can cut better.

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Work hard, play hard, live long.
Outlaw_Dogboy

 
Walt, I saw that issue also. Interesting that predators T-Rex and Great White Sharks have serrated teeth and used them to good effect. Good plug for serrated knife makers everywhere, I'm sure.

Plus I believe both predators grew new teeth to replace the old, so if we extend the knife analogy, I guess history dictates that we should replace our dull serrateds with new ones. If only T-rex and the GWS had been properly equipped with Sharpmaker 204's
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That SciAm article is awfully interesting because it actually investigates the physics of cutting. The author carefully measured the draw and downward force necessary to cut pieces of meat and claims that serrated edges cut in a very different way than smooth edges. He describes the serrated cut as a "grip and rip" mechanism. The teeth penetrate into the meat, then tear across the fibers, penetrate again, etc. The smooth edge simply wedges the meat apart with the drawing of the blade reducing the fiction of penetration. This approach explains the observations that serrated edges excell in cutting strong fibers like rope and boxes. The fibers have such a high tensile strength that they don't separate easily with a smooth blade, whereas the serrated blade tears the fibers apart one by one. We don't really need a scientist to tell us this, do we?

Clearly, the use of a course ground edge as discussed in this forum is intermediate in mechanism between a serrated and smooth edge, since it grips and tears on a microscopic scale.

It was interesting that the author suggested that the serrations on T. Rex's teeth had less to do with cutting than they did with the beast's use of biological warfare agents. Apparently, the teeth are a lot like the Komodo dragon's where the serrations hold on to bits of decaying flesh and fat which serve as food for all sorts of awful bacteria and corruption. This gives the dragon and presumably gave T. Rex very bad breath and periodontal disease and a very infectious bite. Thus even the one that gets away with "just a flesh wound" is struck down within a few days with a terrible infection only to be eaten by the patient lizard and/or his friends.

So it seems to have been scientifically proven that a really filthy serrated blade is the most lethal of all possible.
 
The most lethal blade is the cheap hollow handle survival knife filled with matches; one sticks it in someone and ignites the matches which then blow up.... :^)

I don't think that the issue is settled on serrated vs plain. Even with fibers like rope a very good plain edge seems to do just fine, as one author commented that the Hartsfield (?) A2 blade that he used seemed to cut thru rope with no apparent sensation of force being used. Scapels are usually plain edged but saws seem to be used on bone.
 
Okay, I will have to go get this SciAm article now, but if I may, I'd like to make an "I haven't read it but here's what I think" comment.

The use of infectious agents in T. rex's teeth in a mode similar to the Komodo dragon seems like nonsense. The Komodo dragons occupy a fairly unique ecological setting. They occupy well-isolated small islands that lack any other large predators (excluding humans) but do have a population of large herbivores. The islands also lack large scavengers. This means that a deer (or are they bovids?) wounded by the "dragon" will not be taken by another predator in the days it may take to die, and the likelihood of that same dragon getting to feed on the corpse is also high. The only competition they need worry about is from other "dragons" finding the corpse (and perhaps a few birds that are easily driven away), and this is likely balanced by sharing of the corpse and a degree of mutual "stealing" that regularly occurs.

This situation is very different from T. rex's, where prey could range over a wide area and multiple predators and scavengers abounded. There could not have been the Komodo Dragon's unique luxury of biting on Tuesday what it would eat on Friday. Another predator would surely take the wounded animal, and if it died of the wound other scavengers would likely pick the body clean before T. rex ever got the chance.

I also wonder if the Komodo dragon may have an advantage to its "deadly bite" in being a lizard with rather different bacterial resistance than its mammalian prey. Perhaps for T. rex to have a "deadly bite" to its fellow saurischians and ornithischian cousins, it would have risked infection itself?

It is interesting to note that recent finds of theropods related to T. rex have revealed more agile predators with slimmer, smoother teeth - so clear there is some importance to the character and it may be related to a more scavenging lifestyle in T. rex. If we are to take a cue from the sharks (and many convergent bony fish and mammals) we would believe that pointed, smooth teeth are for grasping prey, while broad, serrated teeth are for tearing out chunks.

-Drew

(I hope taking this "animal attack" turn doesn't get the thread booted to the Community Forum
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[This message has been edited by Corduroy (edited 01 September 1999).]
 
Cougar - Carving is not done by many, or often, but a relatively small plain blade has the "edge". For scraping, I use the back of the blade on my serrated knife. Why bugger up the edge scraping? Chopping (such as food) can be done with multiple slicing (in which case a serrated edge will more often than not work better). And when was the last time you shaved with a knife?

Now Slicing, slashing tearing, ripping or most needs for High Performance Matter Separation are what a knife is used for most often.

Boxes or rope for example are neither; carved, scraped, chopped or shaved.

Not a good comparison with your car that seems to only work on sidewalks.

Drew - smooth pointed teeth are still teeth.

sal
 
Can't resist replying to Drew, but I'll try to relate it to bladed weapons.

The situation with T. Rex is similar to using a throwing knife or arrow compared to a knife to take down a well-antlered deer. The deer might run a great distance after being wounded by an arrow, and you might be able to slash the beast's throat or eviscerate it with the knife, killing it instantly, but the risk of being seriously impailed by the antlers makes the thrown weapon the wiser choice for the career man. Similarly, the highly sophisticated defensive weapons of T. Rex's prey would have made a slash and track approach much safer.

And back to blades. Natural selection has had hundreds of millions of years to perfect cutting devices in critters and clearly serrated devices are the winners by a good margin.
 
On natural selection .... if all one had to work with were bone for material and were content with dismembering critters into any type of pieces parts, as long as they were smaller, then I guess serrations 'win' :^)

A gentleman in another thread has a site on his favorite knives including a Spyderco (?) 440V model, and he commented that the 440V cut so well that he usually used the plain edge as the serrations just got in the way.
 
Sometimes I think telling stories about old cars is more fun than repeating the same old facts, but since the UBB people still haven't fixed the search function they fubared (and I am beginning to suspect they must have their heads up their bungholes)....

You can saw cardboard with a dull serrated edge, with great effort and special vocabulary to turn the air blue with. Another approach is to take a thin blade with a sharp polished edge and zip through it effortlessly, pausing every few minutes to give the edge a couple of strokes. The dialysis patient mentioned above could spare his kidneys, cut twice as fast including touch-up time, and lay off his assistant or put him to work doing something useful....

A dull serrated edge can saw through some kinds of rope, but fails completely on other kinds, just pushing and pulling the fibers back and forth without cutting them no matter how much effort you put into it. A sharp polished edge zips right through any rope of reasonable size in a single stroke with no sawing or special vocabulary required. If I ever have to cut a 4" (10cm) rope I'll whittle through it with several cuts to make clearance for the blade, like a woodsman chopping a tree, with no sawing involved.

A good sharp serrated edge will pushcut just as well -- if you keep it razor sharp. If you do that you'll find the serrations give you no advantage because you'll never saw at anything. Unless you're cutting steak on a plate or sawing bread, the teeth only interfere with sharpening. However, if you sharpen only the unserrated side your only difficulty will be removing the burr from between the teeth, and you'll have the advantage that the teeth will eventually disappear.

-Cougar Allen :{)
 
TDean,

I'm not sure I follow your reasoning, since whether T. rex's teeth were serrated or not it would still have to get in harms way to use them; it doesn't have the luxury of firing a "tooth" into its prey from many yards away. I admit it could deliver one bite and then back off while the prey died, avoiding further risk. This is what great white sharks do when they attack sea lions (which are themselves quite large and dangerous)- deliver one massive bite that removes literally pounds of flesh, then back off and let the animal bleed to death. This occurs in a matter of minutes, however, not days. The bacteria in the Komodo Dragon's teeth are not a fast-acting poison, but simply infect the wound and cause death days later. I cannot imagine this strategy working for T. rex, whose environment contained many opportunistic predators and scavengers. Like the great white's serrated teeth, I can see how T. rex might employ serrated chompers to produce a rapidly fatal blow before backing off, I am merely disputing whether it would have relied on bacteria rather than raw trauma and blood loss to finish the kill.

Mr. Allen,

I agree fully that there is not much a very sharp plain edge will not do well, and as I have said I prefer this on the knives I carry. I will argue that the serrated edge will stay sharp longer, however, by virtue of both its greater edge length and its ability to use a more resilient polished edge without loosing the aggressive "bite" this edge can lack. Also, should a serrated knife be dull and sharpening tools unavailable (this does happen!) it will still function (albeit poorly), while a plain knife will only serve to spread butter.

I recently spoke with my friend and presented him with a nice little Almite Walker from Golden for gentlemanly carry. He announced that he believes his Viele has cut its 1000th refrigerator box, and confirmed that it is so dull it's funny. I admit I'm on the point of taking the knife by force and sharpening it myself, but it's an interesting "experiment in dullness" he has going. Still, he's a "knife guy" and a competent sharpener - he should know better!

-Drew
 
This will go to the point of complete digression, but I'll add that the komodo dragon also wallows in its own feces and this probably contributes to the lethality of its bacterial arsenal.

In contrast, T-Rex probably didn't find the time or the fecal mass (even with yard long turds) to probably "soap up" as did the komodo, and I guess I'd concur with Drew that the bacterial contribution in the T-Rex bite was probably negligible to having a few hundred pounds of flesh removed.

Besides, plain-edged or serrated, knife-knuts are like the Great White Shark in having endless rows of new knives waiting to replace the broken or worn
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I ran across this just now on the Missions site and thought it had the ring of the last word in it. It's from July 1996 KNIVES ILLUSTRATED and it was introduced by our esteemed Moderator, Mr. Glesser. it's a< href="http://www.missionknives.com/articles/Serrations.html"> here. </a> A very good article to explain why serrations are so damn good.

Drew,

I suspect that you've been looking at too many of those intro to geology books that show T. Rex with a dozen or so varieties of pterasaur flying around, ichthyosaurs jumping, a few hadrasaurs, etc. Those pictures illustrate the variety of the critters, they weren't actually stumbling all over themselves like that. Actually the larger the critter, the smaller the population density, and of course huge predators are even more thinly spread out over the land. So if T Rex was tracking our faltering, disease-ridden prey, when it was about to fall over, he/she wouldn't have had many competitors to argue with. And I'd just bet that T. wouldn't have had to have been too bright to track a big triceratops through the forest. In any case, the Sci Am article points out the evidence that shows T. Rex to be likely a full fledged predator, not the scavenger that some scientists thought. Great serrated blades that boy had.
 
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