Can CATRA Predict Rope Cutting Performance?

Larrin

Larrin

Joined
Jan 17, 2004
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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/can-catra-predict-rope-cutting-performance/
 
It's pretty cool to see the correlation between datasets. Is there enough overlap in steels tested to see if the rope tests correlate well with each other or has that already been looked at before?
 
milkbaby said:
It's pretty cool to see the correlation between datasets. Is there enough overlap in steels tested to see if the rope tests correlate well with each other or has that already been looked at before?
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Maybe. I didn't check.
 
Interesting. Among other things, Mr. Sandor's data seems to kind of confirm what we have heard over the last few years about Elmax. It seems to become a completely different critter when the hardness levels get up around 61Rc.
 
jdm61 jdm61 - How about explaining that statement about Elmax @Rc 61. I ask because I have been trying to decide on standardizing my skinners, filet knives, and general backpacking knives in either M390 or Elmax. Edge keeping is a major consideration _ Skin at least 2 deer or 1 elk without sharpening, filet 10-12 Kenai salmon without sharpening, and make a 5 day backpacking trip without sharpening. Peters seems to feel Rc 60 is max for both. What happens to Elmax at around Rc 61 or 62 in your experience? Larrin, you might chime in, too.
Tim
 
tim37a said:
jdm61 jdm61 - How about explaining that statement about Elmax @Rc 61. I ask because I have been trying to decide on standardizing my skinners, filet knives, and general backpacking knives in either M390 or Elmax. Edge keeping is a major consideration _ Skin at least 2 deer or 1 elk without sharpening, filet 10-12 Kenai salmon without sharpening, and make a 5 day backpacking trip without sharpening. Peters seems to feel Rc 60 is max for both. What happens to Elmax at around Rc 61 or 62 in your experience? Larrin, you might chime in, too.
Tim
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In Bohler-Uddeholm's CATRA testing there was a big jump from 60+ (60.5?) and 62 Rc with Elmax. At 62 Rc it had nearly the edge retention of the more wear resistance M390 at 61+. To me it looks like too big of a jump from 60.5 to 62 Rc, and either the 60.5 Rc test underperformed or the 62 Rc test overperformed. In the large CATRA dataset I analyzed I didn't see any similar big jumps with an increase of 1.5 Rc. Alternatively it could be that there is some shift in behavior, I just don't know what that would be.
https://knifesteelnerds.com/wp-content/uploads/2018/08/Bohler-Uddeholm-CATRA.pdf
 
IIRC, the rep from B-U said a few years back that once you go up to 61+, Elmax did indeed have abrasion resistance getting fairly close to M390 ( I think that he said 85-90%) but still retains the advantage in toughness. I talked to him at Blade. this was also when i asked if the dry ice Slurpee was a tad too "warm" for Elmax and he said yes. As for edge keeping, who knows what you need? MY brother and I used a big W2 hunter at like 62 to skin two sand encrusted feral hogs with no need for sharpening. Another knife of the same stuff was used to skin out a nilgai or two. They are elk size.
tim37a said:
jdm61 jdm61 - How about explaining that statement about Elmax @Rc 61. I ask because I have been trying to decide on standardizing my skinners, filet knives, and general backpacking knives in either M390 or Elmax. Edge keeping is a major consideration _ Skin at least 2 deer or 1 elk without sharpening, filet 10-12 Kenai salmon without sharpening, and make a 5 day backpacking trip without sharpening. Peters seems to feel Rc 60 is max for both. What happens to Elmax at around Rc 61 or 62 in your experience? Larrin, you might chime in, too.
Tim
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Larrin said:
In Bohler-Uddeholm's CATRA testing there was a big jump from 60+ (60.5?) and 62 Rc with Elmax. At 62 Rc it had nearly the edge retention of the more wear resistance M390 at 61+. To me it looks like too big of a jump from 60.5 to 62 Rc, and either the 60.5 Rc test underperformed or the 62 Rc test overperformed. In the large CATRA dataset I analyzed I didn't see any similar big jumps with an increase of 1.5 Rc. Alternatively it could be that there is some shift in behavior, I just don't know what that would be.
https://knifesteelnerds.com/wp-content/uploads/2018/08/Bohler-Uddeholm-CATRA.pdf
Click to expand...
 
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