rope cutting and serractions.

J

jjcoolay

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Jul 4, 2002
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I Just tested my small little kershaw scallion on a piece of rope versus a spydie native SE. Now i would have expected the native to far outperform the kershaw but this was the exact opposite.


I know that serraion were meant for line but why did the native perfrom so poorly??
I know that some rope increases its toughness and tension when it is wet. This is where the serrations would come in handy. Is the only incdent where Serrations are good or did the small size of the rope not let the serrations perform at its peak?

The test rope was a 1/4 rope that was quite smmoth, nothing rough.I gripped two strands together and pushed cut the rope with the scallion. I tried that with the native then sawed through

Did I test it wrong or is this an anomly?
 
From the way you describe the cut I think it's beacuse the actual surface cutting area of the scallion on that section of rope was greater than the native.

The native been serrated had those peaks stopping the cutting area of the blade from touching the rope.

Straight edged blades would likely always perform better than serrated edges on a pushcut.
 
I believe it is a myth that serrated blades cut rope better. A sharp plain edge will cut it as well (or, as you point out, sometimes better.) Your test might have mislead you for two reasons. The first is that the level of sharpness (or bevel angle etc.) of the two blades might be different. Dull blades, serrated or otherwise, won't perform well. The second is that you would need to saw with both blades to compare them because serrated edges only work well with a sawing cut while plain edges work well with all kinds of cuts. Had you sawn with both blades the serrated edge might have outperformed the plain edge. So basically, I don't think your test was likely to have proven anything but I think it's cool that you ran the test. Let us know if you run it again.
 
The sharpenings were the same or at least I think they were the same. I forgot to say that I also tried to sawed through the knife with both knives with the same result. The Kershaw came out on top
 
I don't know these knives so I can't comment on this particular test, but I once took two brand new Spyderco Delicas (factory edges), one with a straight edge, and one fully serrated, and sawed both through tensioned 3" thick hemp tug rope. Both knives cut the rope, but the one with the serrations did it in half the number of strokes.

(Edited to add)
I think your rope might be to thin for you to notice the real effect of properly sharpened serrations.
 
Originally posted by Knife Outlet
I believe it is a myth that serrated blades cut rope better. A sharp plain edge will cut it as well (or, as you point out, sometimes better.)
Click to expand...
I agree with one exception - polypropelene line. If your plain edge has too fine of an edge, it will slip off of the line instead of biting; especially on lines that are > 1/2".
 
One of the biggest factors in the increased performance of serrated edges is that they are ground more acute than plain edged knives, often at 1/2 to 1/3 the angle, Steve Harvey was one of the first people to point out this huge geometry difference. If you have a thin plain edged knife of similar edge geometry to the serrated one, you can push through small rope easier and faster than sawing through with a serrated knife. Joe Talmadge was one of the first people to quantify this, noting the high performance of his Spyderco Calypso Jr doing such cutting.

However as Matthew noted, when the rope gets a lot thicker, it becomes very difficult to push cut. You now have to slice it and the serrations will begin to show their true abilities. However if you take a fine plain edged knife, and give it a coarse finish (use a rough stone or a file), it can still hold its own against a serrated knife. Serration patterns do have durability advantages though (and some disadvantages as well), and they can act like weak saws much better than a coarse finished plain edge so they have benefits on sawing wood / plastics and the like.

-Cliff
 
Just to add that in my experience a file sharpned plain edge knife, or as I am using today, a knife with a convex edge sharpened on cardboard backed 60 grit AO sandpaper, will outslice any serrated edge that I have used.
Serrations, depending on design, have a tendency to snag, and are over all less useful for the type of cutting I do.
The one advantge that serrated edges have is in cutting hard plastic or oft metals. As Cliff pointed out the serrations allow you to saw threough. Also the tips act as a guard to protect the scalloped portion.
As has been pointed out, serations are typically ground mure acute )like 1/2) the angle of straight edges, accounting for the difference that some people claim.
 
Hi guys - I thought I would get in to this one if you don't mind.

You will notice that the Scallion has a "reverse" serration.

We have started to use this configuration due to the improved cutting performance.

basically you create a smoother sawing action - resulting in a better cut.

Also, you have a much stronger serration. no serration points to break off.

Enjoy.

Craig Green
Factory Manager
Kershaw Knives.
 
Hmm thats what i thought. My test was stacked in favour of the small plain edge knife. If I had a wet rope, the water tension on the rope would have made it impossible for anything other than a serrated knife to get purchase on the slick surface.
 
I was a commerical fisherman here in Alaska for many years and I tried every knife I could get my hand on . I also spoke to many other fisherman and to a man the serrated cut rope or line better than any plain edge. I always carried 2 knives one under my slicker and a Spyerco serrated rescue model clipped to the top of the bib of my slicker. It was used many times in rough weather when a sandy rope had to be cut quick. One pull was all it took to go through a 1" rope. Just about all the fisherman I know have several of the little 4" serrated Forshners taped to their suspenders or in several places on the boat where they can get to them quickly.
:D
 
I have a Spyd Merlin and it cuts rope like crazy. Supposely the Cold Steel unique micro serrations does a wonder of a job cutting rope. Its pretty impressive the way they cut free suspended rope like butter!!!
 
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