thoughts on CPM D2 (updated)

kane22 said:
Cruwear will be a little tougher, and should have better wear resistance. CPM D2 has more chromium so it should have the edge in corrosion resistance. No first hard experience yet, but that's what I'm thinking.
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About half of D2's chromium is used in carbides. Cruwear is rated by Larrin to have a bit better corrosion resistance than D2.
 
Crag the Brewer said:
Not sure about the Dozier test? Was the edge angle the same? Similar bte? Idk?
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Twindog said:
I was surprised at the Dozier results, too. But Ankerson had an excellent testing protocol. He worked with Phil Wilson to get it down to a science. The edge he used in testing was 30 degrees inclusive, polished with 6,000 grit. Maybe that is too fine a polish for D2.
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6,000 grit it too fine a finish for that testing. In addition, if you look closely at the data, he was testing edge geometry as well as steel. There are some examples in his test results where he took the same knife, reground the edge to be thinner behind the edge, and got significantly better results. That essentially turned it into a two variable test, rather than just a one variable test that only compared steels.
 
lambertiana said:
6,000 grit it too fine a finish for that testing. In addition, if you look closely at the data, he was testing edge geometry as well as steel. There are some examples in his test results where he took the same knife, reground the edge to be thinner behind the edge, and got significantly better results. That essentially turned it into a two variable test, rather than just a one variable test that only compared steels.
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That makes a Lot of sense
 
lambertiana said:
If he had ground all of the blades to the same thickness behind the edge, it would have been a one variable test, comparing specific knives (steels) from specific manufacturers. He did do a good job showing that geometry matters a lot.
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It's almost, Everything...
 
lambertiana said:
6,000 grit it too fine a finish for that testing. In addition, if you look closely at the data, he was testing edge geometry as well as steel. There are some examples in his test results where he took the same knife, reground the edge to be thinner behind the edge, and got significantly better results. That essentially turned it into a two variable test, rather than just a one variable test that only compared steels.
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Yes, that is a fair point. However, Ankerson did show that thinness behind the edge is a major factor in edge performance. He also showed that heat treatment from a master knivemaker was also a big factor. I don't remember anyone proving that before.

And he wasn't testing just the steel -- or comparing various heat treats -- he was comparing the knife's performance from the maker with the edge thickness and heat treat as the maker provided. All he standardized was the edge angle and sharpness. He was showing what kind of edge wear you could expect from various knives as you would buy them and after you put a decent edge angle and sharpness on them.

Larrin's edge-wear tests are a gift to the knife world. But his tests are scientific using TCC abrasion cards. They test for abrasion wear, but not toughness. In the real world, toughness -- and strength -- can prevent or limit micro-chipping and/or rolling and extend the useful life of the edge. A high-abrasion steel might not hold up as well in the wild as a lower-abrasion edge that has more toughness.

Ankerson's tests nicely augment Larrin's work, because they show how various knife edges hold up in real-world use.
 
Twindog said:
Yes, that is a fair point. However, Ankerson did show that thinness behind the edge is a major factor in edge performance. He also showed that heat treatment from a master knivemaker was also a big factor. I don't remember anyone proving that before.

And he wasn't testing just the steel -- or comparing various heat treats -- he was comparing the knife's performance from the maker with the edge thickness and heat treat as the maker provided. All he standardized was the edge angle and sharpness. He was showing what kind of edge wear you could expect from various knives as you would buy them and after you put a decent edge angle and sharpness on them.

Larrin's edge-wear tests are a gift to the knife world. But his tests are scientific using TCC abrasion cards. They test for abrasion wear, but not toughness. In the real world, toughness -- and strength -- can prevent or limit micro-chipping and/or rolling and extend the useful life of the edge. A high-abrasion steel might not hold up as well in the wild as a lower-abrasion edge that has more toughness.

Ankerson's tests nicely augment Larrin's work, because they show how various knife edges hold up in real-world use.
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He certainly showed the importance of geometry. But at first it was not clear that he was testing knives as they come from the manufacturer. The thread is titled "Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope", not ranking of knives. And the OP for that thread also only says ranking of steels. When I saw his results I immediately concluded that it was not a one variable test ranking steels. The original table only listed manufacturer and/or hardness for some of the knives. It wasn't until he later added the second table that showed all steels and which knives they were used in, with hardness and edge thickness for most of them, that it became clearer exactly what was going on. The second table also had the knives at 400 grit finish, which would be much more appropriate for many uses. I find the high polish 6000 grit edges only useful for things like wood carving.

Results in manila that Ankerson measured could well be different from results with the CATRA that Larrin used. Knife edges will behave differently in different media.

Your comment about higher toughness in a lower abrasion resistant steel possibly holding up better in real world use reminds me of my very good results with steels like CPM Cruwear. And the people who swear by steels like AEB-L at 62 Rc may be onto something.

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lambertiana said:
He certainly showed the importance of geometry. But at first it was not clear that he was testing knives as they come from the manufacturer. The thread is titled "Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope", not ranking of knives. And the OP for that thread also only says ranking of steels. When I saw his results I immediately concluded that it was not a one variable test ranking steels. The original table only listed manufacturer and/or hardness for some of the knives. It wasn't until he later added the second table that showed all steels and which knives they were used in, with hardness and edge thickness for most of them, that it became clearer exactly what was going on. The second table also had the knives at 400 grit finish, which would be much more appropriate for many uses. I find the high polish 6000 grit edges only useful for things like wood carving.

Results in manila that Ankerson measured could well be different from results with the CATRA that Larrin used. Knife edges will behave differently in different media.

Your comment about higher toughness in a lower abrasion resistant steel possibly holding up better in real world use reminds me of my very good results with steels like CPM Cruwear. And the people who swear by steels like AEB-L at 62 Rc may be onto something.

​

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That's why I've always liked the tougher steels. In the real world they seem to hold up better, or enough to off set their lower edge holding.
 
iYGdpzI.jpeg

It wasn't that sharp from the factory but it is now. It will whittle hair with ease. I have other knives that feel as sharp cutting phonebook paper, but you have to work harder to get it to grab a hair like that. It seems to have some good bite. So far I'm happy with it.
 
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