Rope Cutting Test Usefulness

[BluntCut MetalWorks]

In the last 8-9 years, occasionally I cut rope to test edge durability but hasn't found result useful. Today I decided to keep cutting until edge (15dps this time) no longer slice phonebook paper. Useful data, nah!

BCMW Re-hardened 65rc Walmart $10 Ozark Trail D2 60rc Knife - 15dps edge, Rope Cutting Test (video link: youtu.be/Z67KapEBMOg)

Your take?

 

[unwisefool]

Don't strike a spark by accident!

 

[knarfeng]

Rope cutting using a single knife provides marginal useful data. But performing the same tests on multiple knives using the same technique can lead to some useful comparison data.

Thread 'Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope'

Nov 24, 2010

What I have done is rank the steels in Categories based on edge retention cutting 5/8" manila rope. We are looking for big differences here, not ranking the steels in order such as 1,2,3,4,5. The categories or groups mean that one can expect those steels in that category to have close to the same performance as the other steels in the same category. The categories are ranked in order by edge retention, category 1 will have better performance than category 2 etc.

The Custom Phil Wilson knives in M390 (62) and ELMAX (62) are not added to the data, they wouldn't fit into any of the...

• Ankerson
• Replies: 3,218
• Forum: Knife Reviews & Testing

• 

 

[BluntCut MetalWorks]

Rope cutting using a single knife provides marginal useful data. But performing the same tests on multiple knives using the same technique can lead to some useful comparison data.

Thread 'Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope'

Nov 24, 2010

What I have done is rank the steels in Categories based on edge retention cutting 5/8" manila rope. We are looking for big differences here, not ranking the steels in order such as 1,2,3,4,5. The categories or groups mean that one can expect those steels in that category to have close to the same performance as the other steels in the same category. The categories are ranked in order by edge retention, category 1 will have better performance than category 2 etc.

The Custom Phil Wilson knives in M390 (62) and ELMAX (62) are not added to the data, they wouldn't fit into any of the...

• Ankerson
• Replies: 3,218
• Forum: Knife Reviews & Testing

• 

I guess - when number of cuts in 200-400 range then result could be useful per given test person+setup. Whereas long cutting session (1+hr) would introduce fatigue; bad technique/impact; excess # of grooves/scores in cutting board, thus not sure how to draw useful data from this.

 

[Twindog]

Thank for all the work you do, Luong.

As Knarfeng says, it can be a useful test if you're comparing a lot of knives, like Ankerson used to do. But you have to have a really clear and accurate ending point. Three thousand cuts gives useful resolution, but only to the extent that it is accurate.

But for practical reasons, it's a pain in the butt to test that way.

 

[lambertiana]

The problem with such tests like that linked above is that they are as much a test of geometry as they are of the steel/knife/heat treat.

 

[Twindog]

I guess - when number of cuts in 200-400 range then result could be useful per given test person+setup. Whereas long cutting session (1+hr) would introduce fatigue; bad technique/impact; excess # of grooves/scores in cutting board, thus not sure how to draw useful data from this.

I don't think you can do it with a range that small. If you look at Ankerson's test, he recorded 2,400 cuts with a Phil Wilson blade of 10V at 64.5 Rc (.004 BTE)

On the other end, he had an Opinel in XC90 at 80 cuts.

The smaller the range, the more precise your end point has to be. And the precision of the end point is usually the weak link in these tests.

 

[Twindog]

The problem with such tests like that linked above is that they are as much a test of geometry as they are of the steel/knife/heat treat.

That's a fair point. If you look at Ankerson's tests, he included the BTE for most of his tests. I think he started adding that measurement because it was quickly apparent to him that the edge width is such an important variable. He always kept the angle constant.

 

[BluntCut MetalWorks]

CATRA removed many rope cutting variables (varying pressure, backing, wedge geometry[angle+BTE+primary bevel+stock thickness), thereby avoid wild variances in rope cutting configuration. Even when sharpening consistency is given/perfected, CATRA still highly correlated to heat treatment and test card stock (iirc ~4% silicate content). It is obvious that per given cross section geometry interact with cutting medium, given perfect apex - best/ideal performer when steel can support lowest angle PLUS thinnest BTE PLUS tallest cross section height. For given ht protocol & geometry, Larrin's CATRA data show TCC is linear proportional to hardness. Well, rope cutting usefulness is questionable, doesn't it? On the positive side, rope cutting complexity reflects closer to real-world use, where CATRA testing is contrived.

 

[me2]

I was testing on cardboard for a long time. I never used rope because it was expensive. The handful of times I did try rope, it didn’t really tell me anything I didn’t already know. Cutting to the point a knife won’t slice light paper means even inexpensive knives can cut for a long time. I went through half a mile of cardboard and a $10 Chicago Cutlery knife and it would still slice notebook paper. Dulling from wear is not linear. The duller an edge is, the slower it gets more dull.

 

[BluntCut MetalWorks]

I don't think you can do it with a range that small. If you look at Ankerson's test, he recorded 2,400 cuts with a Phil Wilson blade of 10V at 64.5 Rc (.004 BTE)

On the other end, he had an Opinel in XC90 at 80 cuts.

The smaller the range, the more precise your end point has to be. And the precision of the end point is usually the weak link in these tests.

I plan to try make slices of green bamboo bundle (cane + leaves) as test 10-30% silicate content medium for testing. This would/could be a good way to test edge endurance(stability & wear)... or not

 

[Twindog]

CATRA is good for abrasive wear, as long as all the confounding variables that Luong mentioned are made equal. In real world use, edge wear comes from denting, rolling and chipping, as well as abrasion.

Those real world variables need different qualities -- more toughness or more strength or different geometry, etc.

Rope tests are better than CATRA for real-world use, but far from perfect, because rope is still pretty easy as far as toughness and strength are concerned.

The best test for edge wear is a test that matches your real world use.

Here is some chipping:

and here is chipping and cracking

 

[Sidehill Gouger]

There is rope and there is rope. What the late Wayne Goddard taught me on was one-inch manila. The problem is a lot depends on edge geometry and the how the knife was sharpened. Many shaving sharp knives will barely scratch the surface of the rope. It is also important that all testing is done on the same one-inch manila to keep things consistent. Heavy rope like this is not always easy to find. I ordered mine in a 100 foot roll from a farm supply store. Synthetic rope is useless for edge testing.

 

[BluntCut MetalWorks]

There is rope and there is rope. What the late Wayne Goddard taught me on was one-inch manila. The problem is a lot depends on edge geometry and the how the knife was sharpened. Many shaving sharp knives will barely scratch the surface of the rope. It is also important that all testing is done on the same one-inch manila to keep things consistent. Heavy rope like this is not always easy to find. I ordered mine in a 100 foot roll from a farm supply store. Synthetic rope is useless for edge testing.

I found cutting 1" dia manila rope is harder but mostly because the rope untwist and move/shift by the edge. I still have some (50-80ft) of 1" dia manila rope but it is for cut in the air test. At any rate, knife in this video also made 20 cuts of 1" dia manila rope as part of a larger test: here is the video link: youtu.be/eQ9sMOiAsME .

If I wrap tape around 1" dia manila rope, it would be more or less equivalent to taping 4x 1/2" dia sisal rope together into 1" dia rope - albeit a lot cheaper.

 

[knarfeng]

Rope is better than cardboard for testing because rope is more uniform. "Cardboard" comes in many grades. And it would need to be virgin cardboard to eliminate variations from contaminants (dirt and such). Even if you have a large stash of the same grade of cardboard, there will be variations in it due to the variation in fiber orientation.

There are many other variables in cutting tests, other than blade steel and test medium.
When I used to perform rope testing myself, I took precautions to remove some of the variables, so that the primary variable was the blade steel.
> All blades were sharpened at 15 dps on a Sharpmaker coarse flat rod (Sal says that's about a 600 grit). So minimal variation in edge angle between blades. And uniform sharpness.
> I marked out a set distance on each blade and made slicing cuts for that distance along the blade. So the same amount of edge was doing the cutting.
> I measured the hardness of each blade on a Rockwell tester So that I knew what I was testing
> I supported the rope with two boards with a slot between them. I performed the cut over the slot so that I was only cutting rope.
> I put a bit of tension on the rope so that it would pull away from the blade as it was cut. This removed the effect of variations in blade profile. A thick blade would cut equal to a thin blade, because only the edge would contact the fibers.
> I made the same number of cuts with each blade and evaluated the performance by looking for changes to the edge under a 3X hand lens.

 

[BluntCut MetalWorks]

Rope is better than cardboard for testing because rope is more uniform. "Cardboard" comes in many grades. And it would need to be virgin cardboard to eliminate variations from contaminants (dirt and such). Even if you have a large stash of the same grade of cardboard, there will be variations in it due to the variation in fiber orientation.

There are many other variables in cutting tests, other than blade steel and test medium.
When I used to perform rope testing myself, I took precautions to remove some of the variables, so that the primary variable was the blade steel.
> All blades were sharpened at 15 dps on a Sharpmaker coarse flat rod (Sal says that's about a 600 grit). So minimal variation in edge angle between blades. And uniform sharpness.
> I marked out a set distance on each blade and made slicing cuts for that distance along the blade. So the same amount of edge was doing the cutting.
> I measured the hardness of each blade on a Rockwell tester So that I knew what I was testing

Agreed - cardboard is wildly inconsistence - that was why I split each piece of cardboard into 2 for cutting comparison. I sharpened with an edgepro at 15dps, 600 grit diamond plate. Yep, I've a hardness tester so hrc was posted.

> I supported the rope with two boards with a slot between them. I performed the cut over the slot so that I was only cutting rope.

Sound good but without board impact, it will take a lot more cut to dull this blade.

> I put a bit of tension on the rope so that it would pull away from the blade as it was cut. This removed the effect of variations in blade profile. A thick blade would cut equal to a thin blade, because only the edge would contact the fibers.

Wouldn't this strain the fibers? Like cutting the stretch side of bend fibers (hm tiny sticks).

> I made the same number of cuts with each blade and evaluated the performance by looking for changes to the edge under a 3X hand lens.

Not sure if visual precision is useful here, since rope cutting is mostly qualitative backed by fuzzy counts/quantity.

 

[sodak]

So what exactly is the point of this thread? To disqualify all rope testing that has been done by others in the past?

You want to use bamboo instead of rope. How do you ensure uniformity among test cutting samples?

 

[BluntCut MetalWorks]

So what exactly is the point of this thread? To disqualify all rope testing that has been done by others in the past?

You want to use bamboo instead of rope. How do you ensure uniformity among test cutting samples?

Well, if rope is somewhat abrasive medium then this D2 blade wouldn't made 3+K cuts. So yeah, numerous tests in 8-9 years, I don't find this test useful neither in toughness nor wear resistance benchmark.
Bamboo is high in silicate [ stalk/cane up to 4%, leaves 30-50% by weight], combine hardness+stiffness of cane and high silicate%, which would test both edge stability and wear resistance. Whereas CATRA only abrasive/wear. Obvious this test medium won't be uniform nor consistency even at each cut, however it could be very useful when doing side-by-side comparison between N blades by alternate every M # of cuts(e.g. switch blade every 10 cuts). CATRA measures wear resistance in TCC (in mm), for this test medium would also measure wear resistance in mm and also subject must not fail toughness aspect when cutting through cane includes its eye/knot. Also by keep lowering the edge angle & BTE until 1 or 2 subjects didn't fail first few cuts, which give data on edge strength along with wear resistance#. When keep edge angle&BTE 15-18dps where edge passed at lower finished grit, now increase finish grit (higher keen/sharpness) until most edges take damage early, this would reveal steel toughness(strength+good elastic range).

 

[sodak]

Testing over the last 20+ years, I find rope testing very informative in determining wear resistance. I've never tested for edge stability, but don't worry about that. Rope can be fairly uniform when testing from the same batch. But bamboo, I would be very curious to see how each batch could be tested against each other, since it's not a consistent medium.

Don't be so quick to dismiss a ton of rope testing done in the past. There is a lot of information to be gleaned from it.

 

[BluntCut MetalWorks]

Testing over the last 20+ years, I find rope testing very informative in determining wear resistance. I've never tested for edge stability, but don't worry about that. Rope can be fairly uniform when testing from the same batch. But bamboo, I would be very curious to see how each batch could be tested against each other, since it's not a consistent medium.

Don't be so quick to dismiss a ton of rope testing done in the past. There is a lot of information to be gleaned from it.

When working/useful for you and others, all is good then.