Analysis of Recent M390 CATRA Testing

[Larrin]

The minor controversy with hardness and edge retention of different M390 knives led to two different small CATRA studies on M390 knives, and one knife in S30V. I went through both of them including what was measured and a couple small surprises. https://knifesteelnerds.com/2019/10/07/ ... 90-knives/

[Sharp Guy]

Thanks Larrin! Interesting read, as usual

[Dazen]

Thank you for reassuring me that I should keep my M390 knives, and Nice Work!

[Naperville]

Thank you for the article. I love reading them.

[Naperville]

Mmmmmmm M390 and S30V are good steels to write about.

[JonLeBlanc]

Always fascinating!

[Larrin]

Thanks guys, glad you like the analysis of the interesting testing.

[Doeswhateveraspidercan]

Interesting article but I am not the brightest bulb in the socket. Could you please tell me which angle inclusive was found to be best by the testing? I am pretty sure I am misunderstanding this but it looks like 20 degrees inclusive or 10 degrees per side.

In addition it appears 600 grit described as 40 microns proved best but I have yet to find a purchasable stone declaring 600 grit to be 40 microns

In fact I am seeing a much smaller micron rating like 16 microns equating to 600 grit for example from the Wicked Edge company https://support.wickededgeusa.com/porta ... ison-table

DMT is showing their coarse stone at 45 microns maybe I missed something but what stones were they using in the test with to report 40 microns as 600 Grit. https://www.dmtsharp.com/resources/dmt-faq/

The reason I ask is out of a desire to reproduce the results and to do that I need to purchase the stones used in the excellent write up you have provided.

Thank you.

[Larrin]

Interesting article but I am not the brightest bulb in the socket. Could you please tell me which angle inclusive was found to be best by the testing? I am pretty sure I am misunderstanding this but it looks like 20 degrees inclusive or 10 degrees per side.

In addition it appears 600 grit described as 40 microns proved best but I have yet to find a purchasable stone declaring 600 grit to be 40 microns

In fact I am seeing a much smaller micron rating like 16 microns equating to 600 grit for example from the Wicked Edge company https://support.wickededgeusa.com/porta ... ison-table

DMT is showing their coarse stone at 45 microns maybe I missed something but what stones were they using in the test with to report 40 microns as 600 Grit. https://www.dmtsharp.com/resources/dmt-faq/

The reason I ask is out of a desire to reproduce the results and to do that I need to purchase the stones used in the excellent write up you have provided.

Thank you.

I'm confused as well because edge angle and grit were not variables tested. A target edge angle of 34° was used with small variation. All were sharpened to the same grit. Perhaps you are talking about this article: https://knifesteelnerds.com/2018/06/18/ ... retention/

There isn't really a "best" edge angle. More acute is better for any CATRA test I've ever seen. Presumably there is some point where the edge is so thin it rolls or chips in the CATRA test but I haven't seen what point that is.

A mistake in an article in terms of converting grit to micron is always a possibility. That article was written last June and my memory of grit conversion charts from last year isn't very good.

[Albatross]

No idea how accurate this is, but it's what I've used for micron to grit conversions.


http://www.rahulgladwin.com/docs/micron ... ersion.php

[Doeswhateveraspidercan]

No idea how accurate this is, but it's what I've used for micron to grit conversions.


http://www.rahulgladwin.com/docs/micron ... ersion.php

Thank you I found this site as well and it is very close. Wicked edges declarations of micron size are all over the place.

https://www.gemsociety.org/article/gem- ... h-microns/

[JD Spydo]

Larrin thank you again for sharing this great and timely information with us. The information on these blade steels that you share with us is just about to inspire me to go back to college and take more metallurgy classes. I've taken a 101 and 102 rated courses in the past which probably gave me enough knowledge to be dangerous :D But you present these facts in a really intriguing and interesting manner that is relatively easy to understand.

I've been really hung up on my M390 Military for going on 3 years now. And for the types of cutting chores I encounter on a daily basis I've yet to find a blade steel I like more than M390. Oh I'm sure there one or two out there that I just haven't got to try yet but I think I'll be using M390 blades for a long time to come because that steel just really works well for me bottom line.

[Albatross]

No idea how accurate this is, but it's what I've used for micron to grit conversions.


http://www.rahulgladwin.com/docs/micron ... ersion.php

Thank you I found this site as well and it is very close. Wicked edges declarations of micron size are all over the place.

https://www.gemsociety.org/article/gem- ... h-microns/

No problem. I came across that site as well, but preferred the ability to input numbers that are not on the chart. Just personal preference, as both conversion methods seem to work.

As far as the Wicked Edge discrepancies, I can only speculate, but it makes me wonder. Whatever the reason, a manufacturer of guided sharpeners(or any other type) needs to fully understand grit/micron/mesh, especially if they plan to advertise these things.

[Larrin]

Larrin thank you again for sharing this great and timely information with us. The information on these blade steels that you share with us is just about to inspire me to go back to college and take more metallurgy classes. I've taken a 101 and 102 rated courses in the past which probably gave me enough knowledge to be dangerous :D But you present these facts in a really intriguing and interesting manner that is relatively easy to understand.

That's awesome! Hopefully the website is easier to understand than a textbook. :)

[Cycletroll]

Thanks Larrin! As usual an objective and circumspect treatment. I really appreciate your discussions of the gathered data as well as the cautions against unsubstantiated inferences.

[Larrin]

Thanks Larrin! As usual an objective and circumspect treatment. I really appreciate your discussions of the gathered data as well as the cautions against unsubstantiated inferences.

I do my best!

[Doeswhateveraspidercan]

No idea how accurate this is, but it's what I've used for micron to grit conversions.


http://www.rahulgladwin.com/docs/micron ... ersion.php

Thank you I found this site as well and it is very close. Wicked edges declarations of micron size are all over the place.

https://www.gemsociety.org/article/gem- ... h-microns/

No problem. I came across that site as well, but preferred the ability to input numbers that are not on the chart. Just personal preference, as both conversion methods seem to work.

As far as the Wicked Edge discrepancies, I can only speculate, but it makes me wonder. Whatever the reason, a manufacturer of guided sharpeners(or any other type) needs to fully understand grit/micron/mesh, especially if they plan to advertise these things.

Agreed and thanks Larrin It was from the link you posted within the article. Appreciate the time and effort. Had to read it a few times but it sunk in.