Rope Cutting

[UnknownVT]

The other day I cut away some sisal/hemp rope off of a rope rug (used as a door-mat) that was fraying and tripping up people - I used my EDC Victorinox - and it was pretty unremarkable - the knife did its job fine.

But on the same evening I was idling looking at the knife and thought I could see some shiney flats on the edge.

Using a Tasco 30X illuminated microscope, to my shock, there were indeed shiney flats on the edge - enough that mere stropping would not remove them (rough side of the strop is loaded with jeweller's rouge), and I had to resort to using the fine (white) crock sticks to bring the edge back.

So was the edge of the SAK so "fragile" that a mere two strokes on some sisal/hemp rope would damage the edge?

This evening I had to do the same thing and cut away another 2 long lengths of rope from the same rug (4 cuts) - but I took them home with me this time.

I again examined my EDC SAK and, as expected, there were shiney flats on the edge.

So I test cut the sample rope I brought home with a couple of other knives to see the effect.

Kershaw Vapor - with combo edge to see how the plain and serrated edge coped, and a Gerber ATS-34 E-Z-Out to see how a premium steel would perform.

Note I was NOT interested in cutting until the blades became too dull to cut any further. I merely wanted to see with a few limited cuts how the blade edges looked under the 30x microscope.

left to right - sample of sisal/hemp rope and cut pieces; Kershaw Vapor; Gerber ATS-34 E-Z-Out; Tasco 30X illuminated microscope

I formed a loop with the rope holding with my hand and cut off a piece about 2" long. Then lay that piece on a cutting board and cut off about 1/3" pieces - ie: 5 cuts. So each blade made a mere 6 cuts.

Cutting the loop - both the plain edges made the cut cleanly. The serrated edge caught the rope and really only cut with one concave section/serration - although it did it cleanly - it did not feel as clean as the plain edges.

Cutting the section to pieces on the cutting board the plain edges did it well with sawing strokes.

The serrations points were too high for the small diameter rope to cut well - so I did not proceed any further with the serrated edge.

Looking at the edges after these minimal cuts I also saw shiney flats on the plain edges BOTH on the AUS-6A blade of the Vapor and the ATS-34 blade of the Gerber E-Z-Out.

This really should not have come as too much of a surprise - because thinking of it - that door-mat rope rug has seen years of use - as evidenced by its fraying condition - it is always very dusty/dirty - that could explain why my knife edge was damaged so quickly - the rope was most probably loaded with fine abrasive dirt/grit.

So it really didn't matter if it was Vic SAK steel, humble AUS-6A or even premium ATS-34 - the edge is going to get damaged. Although to be fair the blades were still cutting the grit loaded rope fine after a practical number of cuts/strokes that one would typically use a pocket knife for.

Any comments, similar experiences?

 

[calyth]

Well you'd probably find some more household items that would seriously dull your knives.
If you got something that you keep a pristine edge, don't use it as a steak knife. The ceramic will wreck an edge pretty quickly.

 

[Cliff Stamp]

Normal hemp rope can be cut for awhile under you can see edge deformation by eye. However dirty rope can produce it in just one cut regardless of steel as you could be cutting rocks. Try used carpet. The living room carpet was replaced awhile back and I cut it up into strips for packing. This actually worse a visible notch in the edge knife I was using, a large faction of a mm deep.

-Cliff

 

[UnknownVT]

Originally posted by Cliff Stamp
Normal hemp rope can be cut for awhile under you can see edge deformation by eye. However dirty rope can produce it in just one cut regardless of steel as you could be cutting rocks. Try used carpet. The living room carpet was replaced awhile back and I cut it up into strips for packing. This actually worse a visible notch in the edge knife I was using, a large faction of a mm deep.

Yes, that's exactly why I was at first surprised (shocked even) to find my trusty SAK with flats after only probably a couple of cuts on what I thought was just hemp/sisal rope.

That is until obviously I thought about it and realized that the "rope" was going to be loaded with abrasive dirt/grit.

I then had to "prove" this to myself - by using known steels and different configurations - hence the ATS-34, AUS-6A and serrations.

Used carpeting is a very good example too, I found a "Stanley" replacable blade knife needed changing far more often than usual - and I hadn't even thought about the effect of the (now obvious) abrasive dirt/grit - and just used to think carpet was tough stuff........

Thanks

 

[Pinoy Knife]

Rope Cutting . well i compete in rope cutting competition's and will say the edge need's to be different for rope than anything else . The blade shape for my rope cutter is way different than any other's who compete , think of a carpet or tile knife , slight hook at tip . the heat treat can be very tricky to get a good rope cutter not something i would expect from any " Factory knife". Just sharing my Experience / opinion's here

 

[Cliff Stamp]

For regular rope cutting, high performance requires a proper sharpening, optomizing the grit choice, and the minimal edge configuration.

On a slice you want the maximal aggression which allows a smooth draw. I have found 100 AO to be very good, 40 grit Diamond to be too coarse. 80 grit AO might be better than 100, have not tried it. The edge just needs to be as thin as possible, I have used ~5 degrees per side on D2 at 62 HRC.

With a knife made out of mild steel, not hardened, I have cut 126 slices of 3/8" hemp on a two inch draw, with an increase of ~20 lbs through the cuts. That knife was also damaged due to previous bending, and the angle less than optimal, too obtuse at 12-15 degrees per side - so its not the performance limit for that steel.

If you are push cutting rope instead of slicing you want a high polish, same angle criteria. The same general rules apply to slicing or push cutting any material. The critical durability requirement is to not make the edge so thin or acute it collapses too readily.

-Cliff

 

[UnknownVT]

Originally posted by Pinoy Knife
well i compete in rope cutting competition's

Since I have "discovered" that a dirty rope can be very abrasive and easily damage any steel knife edge....

So what, if anything, is done to ensure that the ropes used in rope cutting competitions are equal and uncontaminated?

Wouldn't any competitor that got a very dirty rope (abrasive dirt/grip loaded) be at a severe disadvantage?

Thanks

 

[Don M]

Dirt in the rope could explain it. However, before you make general statements about all steel, remember that the SAK is soft (55-56?), the AUS6A is the same or not much harder, and despite the fact that the Gerber has ATS-34, I question how well Gerber heat treats their blades (based on personal experience with Gerber).

 

[Don Luis]

My daughter has been in a Scout-like local group for many years and uses lots of sisal.

To cut it I often use a Camillus demo, I preffer using that one as a beater rather than a SAK and it seems to hold the edge a bit longer. I also sometimes use a rigging knife.

A lot of the kids use cutters or cheap steak knives with fine serrations, they get dull fast, but a couple of passes on a coarse stone can get them back in usable shape.

 

[UnknownVT]

Originally posted by Don M
Dirt in the rope could explain it. However, before you make general statements about all steel, <snip> and despite the fact that the Gerber has ATS-34, I question how well Gerber heat treats their blades (based on personal experience with Gerber).

No general comments here -
here's a very specific comment,
done at great personal sacrifice -

Same 6 cuts -
one to sever a 2" length,
then five sawing slices of about 1/3" on same cutting board.

Steel = ATS-34 -

Result - edge damaged - visible and obvious shiney flats under 30x magnification, as well as score marks on the polished edge face - that are not visible on parts of the blade that were not used for cutting -

Casting aspersions/doubts -
Is the knife and steel heat treatment trust-worthy?

I leave it for you to draw your own conclusions.

Chris Reeve small Sebenza - ATS-34 steel - the fact I could see score marks on the polished edge face was a hint, since Sebenzas have polished edges.

Now I'll have to go polish the edge on that small Sebenza.

Stropping alone did not remove all the shiney flats - although it did polish out the score marks on the edge face.

Had to resort to light strokes on fine white crock-sticks to remove all the flats and final polish out on the strop.

 

[Alberta Ed]

Dirty rope, sisal footmats and old carpet are probably some of the most abrasive materials you can find and will likely take the edge off any steel except for Unobtanium . Animal hide is also usually very gritty, at least, moose and black bear are. So would be anything you have to drag, if you don't have any snow. Trying to saw through that stuff instead of slitting from the inside out will take any edge off quite quickly.