Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

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Larrin
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Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Larrin » Mon Dec 02, 2019 9:14 am

New article about super hard high speed steels. I included information on the history of the development of these steels. Toughness and edge retention values on Maxamet, and a comparison with the toughness of Rex 121. Also a comparison with other knife steels in terms of toughness, edge retention, etc. https://knifesteelnerds.com/2019/12/02/ ... explained/
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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby The Meat man » Mon Dec 02, 2019 9:31 am

Thank you Larrin! Great read and very informative.
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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Enactive » Mon Dec 02, 2019 10:02 am

Awesome, Larrin! Thanks for your work. I read it once, but will have to read again for better understanding.

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby JD Spydo » Mon Dec 02, 2019 10:32 am

Again Larrin another great thread :) Since I had my ups and downs with ZDP-189 I've kind of strayed away from exceedingly hard steels. It seems like many of those super hard steels have an Achilles Heel when used as a knife blade steel. At least that's been some of my own experience anyway.

Oh I like stuff in the Rc 59 to 62 range but it seems like when you go higher than that there are a lot of trade offs with overall performance.

But this is great information as you always are so gracious to share with us.

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Larrin » Mon Dec 02, 2019 10:57 am

JD Spydo wrote:
Mon Dec 02, 2019 10:32 am
Again Larrin another great thread :) Since I had my ups and downs with ZDP-189 I've kind of strayed away from exceedingly hard steels. It seems like many of those super hard steels have an Achilles Heel when used as a knife blade steel. At least that's been some of my own experience anyway.

Oh I like stuff in the Rc 59 to 62 range but it seems like when you go higher than that there are a lot of trade offs with overall performance.

But this is great information as you always are so gracious to share with us.
For certain steels they can maintain quite good toughness even up to 64 Rc or so. In the 66 Rc and beyond though there are definitely limits.
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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Pancake » Mon Dec 02, 2019 11:57 am

Larrin, another excellent article!
I think we are very fortunete that Spyderco is not afraid to work with Maxamet and it´s crazy when you think about it that you have one the best edge holding steel in production knife.

HAP 72 would be cool as a Seki-City sprint run.
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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Larrin » Mon Dec 02, 2019 11:59 am

Pancake wrote:
Mon Dec 02, 2019 11:57 am
Larrin, another excellent article!
I think we are very fortunete that Spyderco is not afraid to work with Maxamet and it´s crazy when you think about it that you have one the best edge holding steel in production knife.

HAP 72 would be cool as a Seki-City sprint run.
I agree Spyderco is probably the best production company in terms of providing a diverse array of steel options, often in sprint runs, to please the steel nerds. I'm sure it's not cheap or easy to do.
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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby The Mastiff » Mon Dec 02, 2019 12:33 pm

Great read Larrin, thanks! This article covered some things I have tried to look up over the years. It's easy to get info on the more well known steels but the old ones that are no longer used have been largely forgotten. You must have a better library than I do. :)

Joe

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Larrin » Mon Dec 02, 2019 12:45 pm

The Mastiff wrote:
Mon Dec 02, 2019 12:33 pm
Great read Larrin, thanks! This article covered some things I have tried to look up over the years. It's easy to get info on the more well known steels but the old ones that are no longer used have been largely forgotten. You must have a better library than I do. :)

Joe
For steel history I have had to work really hard. Getting articles that are not available digitally and obviously are not searchable. When patents are available that makes it easier but even finding those is more challenging than I expected. It took me several months to find the patent for D2, for example. But there are many common tool steels without patents and you have to track down contemporary journal articles. Most articles by metallurgists do not cite the history of a steel in it, and most of them do not know the history. At best you might get, "D2 has been used for several decades for dies." I believe I may know more about the history of tool steel than anyone alive. If anyone knows more I would definitely like to know who they are because they could have saved me a lot of time. Certainly searching the Wikipedia is going to tell you almost nothing.
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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby emanuel » Mon Dec 02, 2019 12:51 pm

Awesome I'll read this tonight once I get home and relax a bit.

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby ABX2011 » Mon Dec 02, 2019 1:02 pm

Very interesting. Thanks.

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Pelagic » Mon Dec 02, 2019 3:55 pm

Thanks once again!
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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Naperville » Mon Dec 02, 2019 4:00 pm

Thank you, always. As usual, I'll have to read it several times to digest the material completely.
Spyderco Collection: Military (S110V), Bob Lum Darn Dao(CPM-154), Yojimbo 2 (1 in S30V & 2 in 20CV), Sustain(20CV), Native 5(Maxamet), Jumpmaster 2(H1), Province(4V). SHORT LIST: CF Shaman(S90V), Native Chief, Street Bowie(4V at 60+ HRC), Nightstick, Yojumbo.

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby curlyhairedboy » Mon Dec 02, 2019 6:01 pm

Thanks again Larrin!
EDC Rotation: PITS, Shaman, CF S90v Shaman, Ikuchi, Amalgam, CruCarta Shaman, Lil Native, Sage 5 LW, 4V Shaman, Watu, Rex 45 Shaman, Rex 45 Lil Native, Caribbean Sheepsfoot CQI, Waterway, Tanto PM2, CQI Kapara
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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Cambertree » Mon Dec 02, 2019 6:10 pm

Thanks for another great article, Larrin. The historical aspect of your research is greatly appreciated.

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby The Mastiff » Mon Dec 02, 2019 9:12 pm

For steel history I have had to work really hard. Getting articles that are not available digitally and obviously are not searchable. When patents are available that makes it easier but even finding those is more challenging than I expected. It took me several months to find the patent for D2, for example. But there are many common tool steels without patents and you have to track down contemporary journal articles. Most articles by metallurgists do not cite the history of a steel in it, and most of them do not know the history. At best you might get, "D2 has been used for several decades for dies." I believe I may know more about the history of tool steel than anyone alive. If anyone knows more I would definitely like to know who they are because they could have saved me a lot of time. Certainly searching the Wikipedia is going to tell you almost nothing.
I didn't get as far as you have and I have tried researching the M and t series for several years. There may be some university libraries here and there that benefited from some retirees donated papers but largely the only information online is more inclined to be advertising than reference material. I even bought a 1920's era salesman's General Catalog ( Tool and special steels : Vanadium Alloys Steel Co., Colonial Steel/Anchor Drawn) on Ebay in my pursuit as an example of the places I've looked. So far your writings have the most comprehensive info I've found so thanks! :)

Joe

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby sal » Mon Dec 02, 2019 10:58 pm

Hi
Larrin,

Excellent!

Thanx for posting here and sharing your hard work. I also found the CATRA accurate in most cases, from our own research. Also your "predictions" were also good.

We are pleased to be able to provide many of these steels in blade formation so those interested can actually use and test the steel on their own.

sal

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby BornIn1500 » Tue Dec 03, 2019 12:07 am

A big takeaway for a laymen like me is
Maxamet with a value of 222 for 68 Rc has approximately 2.2x the edge retention of 440C at 59 Rc if both have the same edge geometry and sharpening.
Maxamet will only cut twice as long as 440C. :eek: I'll stick to my softer steels. It really doesn't seem worth the hassle of decreased toughness and being harder to sharpen just to get 2x the cutting.

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby husq2100 » Tue Dec 03, 2019 5:05 am

Thank you Larrin for the info and to the spyderco team for giving us the varities.

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Re: Super Hard (70 Rc) High Speed Steels – Maxamet, Rex 121, and More Explained

Postby Cambertree » Tue Dec 03, 2019 6:05 am

BornIn1500 wrote:
Tue Dec 03, 2019 12:07 am
A big takeaway for a laymen like me is
Maxamet with a value of 222 for 68 Rc has approximately 2.2x the edge retention of 440C at 59 Rc if both have the same edge geometry and sharpening.
Maxamet will only cut twice as long as 440C. :eek: I'll stick to my softer steels. It really doesn't seem worth the hassle of decreased toughness and being harder to sharpen just to get 2x the cutting.
That's an interesting point and well worth further discussion on the forum, I think. Especially as lower carbide steels will have greater edge stability at more acute angles - which in turn has a strong influence on edge retention.

It's probably veering a little off topic for this thread - sorry Larrin - but I'm reminded of this experiment by Cliff Stamp, where he tested how much more acute the microbevel angle of VG10 needed to be to match the edge retention of S30V on 1/2" manila hemp rope.

The answer was a mere 2 1/2 degrees. Yep, that's right - just by applying a slightly more acute microbevel angle, VG10 would match S30V. Then consider the ease of resharpening and relative toughness, too.

https://youtu.be/OSDFLgq4EDs

The implication is that sharpening a lower carbide volume steel to an even more acute angle may outstrip the edge retention of a higher carbide volume/more wear resistant steel, which requires a more obtuse edge angle to stay stable.

Don't get me wrong, I love that Spyderco provide these interesting high hardness, high carbide volume steels for us to play with, but there's certainly something to think about in Bornin1500 and Cliff's points.


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