Can CATRA Predict Rope Cutting Performance?

[Larrin]

There has been some question about whether CATRA is a useful test for actually predicting the edge retention of a knife. After all, it is a test performed by a robot, not a human, and the knife cuts cardstock with sand in it, which doesn't seem like a very realistic material. So I took three big datasets where people reported their own rope cutting experiments, and then compared those with what we would expect a CATRA test to tell us. https://knifesteelnerds.com/2019/02/11/ ... rformance/

[ferider]

Your comparison/correlation with Ankerson's test in particular is spectacular, Larrin. Thanks for doing this !

[NickShabazz]

This is wonderful, thanks for doing the math :)

[Pelagic]

This really highlights edge retention being largely about stability. Low alloy steels with great geometries didn't do well, and super steels with sub-optimal geometries only did ok. Combine the two (along with hardness), and you have something impressive.

[Larrin]

This really highlights edge retention being largely about stability. Low alloy steels with great geometries didn't do well, and super steels with sub-optimal geometries only did ok. Combine the two (along with hardness), and you have something impressive.

Yes, definitely can't look at only the steel type for predicting knife performance. Edge geometry is more important than steel.

[Pelagic]

This really highlights edge retention being largely about stability. Low alloy steels with great geometries didn't do well, and super steels with sub-optimal geometries only did ok. Combine the two (along with hardness), and you have something impressive.

Yes, definitely can't look at only the steel type for predicting knife performance. Edge geometry is more important than steel.

True, it just has to be able to maintain that geometry. The AEB-L, while ground incredibly thin, did horribly. Thanks for another great article.

[Bill1170]

Thanks, Larrin! Jim Anderson must be pleased at the high correlation between his rope tests and the CATRA card tests. What edge finish is regulation for CATRA testing, toothy or polished? I seem to recall Jim writing that the 400 grit SiC edge outperformed a polished edge on rope.

[Larrin]

Thanks, Larrin! Jim Anderson must be pleased at the high correlation between his rope tests and the CATRA card tests. What edge finish is regulation for CATRA testing, toothy or polished? I seem to recall Jim writing that the 400 grit SiC edge outperformed a polished edge on rope.

There is no standard for CATRA. Coarse edges are probably more common.

[Bill1170]

Thanks, Larrin! Jim Anderson must be pleased at the high correlation between his rope tests and the CATRA card tests. What edge finish is regulation for CATRA testing, toothy or polished? I seem to recall Jim writing that the 400 grit SiC edge outperformed a polished edge on rope.

There is no standard for CATRA. Coarse edges are probably more common.

Interesting. I guess that makes for good A/B testing opportunities, if one has CATRA access.

[The Meat man]

Thank you Larrin! Very interesting to see how the various "informal" testing measured up with the CATRA testing. That is an impressive amount of data to work through.

[Zatx]

Another great study and read, Larrin.

In particular, I agree with your thoughts about LC200N. You said,

"Steels that did better than expected based on the CATRA prediction include LC200N and CPM-M4. I don’t have a good explanation for the good performance of LC200N, which made about 230 cuts vs its predicted position at about 100 cuts."

I'm equally stumped, but my experience with this steel is identical.

I would love to see more about LC200N (I've taken to calling it a "miracle" steel). Since I received a new SpydieChef, it has rocketed to the top of my favorite blade steels. This steel is incredibly easy to sharpen and resharpen/touch-up, yet its edge retention is coming in around the same as the march harder to sharpen CPM S35V. I don't know anything about its cost, but I would love to see Spyderco consider making this their "default" steel in place of using S30V. Again, I'm ignorant of the specifics, but I would posit that any slight cost increase in the metal would be made up by less wear and tear on their equipment in working with it. Plus, it doesn't rust (at least from every test I've seen)!