M398 the brittle brother?

[BeggarSo]

I recently purchased a PITS2 M398 and the edge is a bit obtuse with narrow bevels. Probably in the 18 degrees or higher without measuring.



Kind of assuming this might be due to difficulties with shaping the stuff.

So I am preparing to do a reprofile maybe as low as 15 degrees using my CBN Stones and Hapestone RS.

I have been able to get away with starting at 150 grit or so but reading about the brittle nature of this steel looking for some advice on where to start maybe 300 Grit? IDK.

Where would you start?

I like this picture for the colors Military S90V Bento Box Shop blue I stone washed and Scandi ground it, it was a used knife with messed up bevels so I turned it into a project knife. Not pretty had to take off alot of steel which taught me how wear resistant S90V really is.

Cutlery Shoppee REX121 Wharncliffee reprofiled came in not fully apexed at the heel. SE Endela K390 great steel. And ofcourse the PITS2.

[silver & black]

I really don't find any steel "hard" to sharpen. Some just take more time because they are so hard.

[BeggarSo]

I was thinking more along the lines of maybe causing chips with too low of a grit.

[silver & black]

I usually start with 400 grit on these types of steels. It takes some time to get a burr. More times than not, I finish with 600 grit. Sometimes I will go to 1200 grit... never more than that. I strop with 6 micron diamond solution and finish with 1 micron solution. I find most of these "super steels" do best with a corser finish. That's just me. You might find a finer, more polshed edge to your liking. I think the harder steels "slick out" with a finer finish.

[BeggarSo]

That is a really good observation "SLICKING OUT" YES I believe you are right I have noticed this also.

Thanks.

[vivi]

I was thinking more along the lines of maybe causing chips with too low of a grit.

In all my decades of sharpening I've never come across a steel that chips out when sharpening at low grits (80-200). Whether by hand on diamond plates or on a powered belt sander.

Have you?

[Brock O Lee]

Very hard high-carbide steels like Maxamet does not play well with coarse grits. It leaves a damaged and fractured apex that is not repaired when you eventually finish on finer grits. There are several reports around about this. The workaround was to apex on a higher grit with very light pressure.

When I sharpened Maxamet recently, I progressed from coarse (160) to med (600) to fine (1000), but only apexed and raised a burr on the fine stone. It took a bit longer to apex. You could try 600 or 300 and see how it goes.

I'm not sure if M398 is as finiky as Maxamet... I don't have any.

[Red Leader]

If you notice in the 2026 Catalog, the Nand, Cobol, and P.I.T.S. 2 all have an 'M390' designation. The switch is probably coming.

[BeggarSo]

Yep Blade H.Q. is already selling the M390 version.

As to low grit chipping I have not done Maxamet, nor M398, so that is why I am asking about low grit chipping.

I did redo REX121 starting at 150 grit without problems. But I dont think it is brittle like the Maxamet reports. M398 does seem a reason for caution though.

[vivi]

Very hard high-carbide steels like Maxamet does not play well with coarse grits. It leaves a damaged and fractured apex that is not repaired when you eventually finish on finer grits. There are several reports around about this. The workaround was to apex on a higher grit with very light pressure.

When I sharpened Maxamet recently, I progressed from coarse (160) to med (600) to fine (1000), but only apexed and raised a burr on the fine stone. It took a bit longer to apex. You could try 600 or 300 and see how it goes.

I'm not sure if M398 is as finiky as Maxamet... I don't have any.

I know there are reports about this. I was just wonderi g if he had personally experienced it.

I've read reports about a lot of things that I've never personally witnessed when it comes to sharpening. X steels chipping out at low grits, carbide tear out, X steel liking a toothy edge, X steel not being able to hold a 30 degree inclusive edge etc.

I feel like a lot of these things just get accepted as fact by the knife community but when you dig around there's rarely people with personal experience with them.

[Bill1170]

Very hard high-carbide steels like Maxamet does not play well with coarse grits. It leaves a damaged and fractured apex that is not repaired when you eventually finish on finer grits. There are several reports around about this. The workaround was to apex on a higher grit with very light pressure.

When I sharpened Maxamet recently, I progressed from coarse (160) to med (600) to fine (1000), but only apexed and raised a burr on the fine stone. It took a bit longer to apex. You could try 600 or 300 and see how it goes.

I'm not sure if M398 is as finiky as Maxamet... I don't have any.

I know there are reports about this. I was just wonderi g if he had personally experienced it.

I've read reports about a lot of things that I've never personally witnessed when it comes to sharpening. X steels chipping out at low grits, carbide tear out, X steel liking a toothy edge, X steel not being able to hold a 30 degree inclusive edge etc.

I feel like a lot of these things just get accepted as fact by the knife community but when you dig around there's rarely people with personal experience with them.

I have seen the same thing. Direct experience trumps vague internet lore.

My own experience tells me that super hard high-carbide steels demand a more gradual grit progression than softer steels do. Otherwise you spend an eternity on the finer grits trying to erase the deep scratches left by the coarser stones. Plus, these alloys essentially force you into diamonds or CBN and those super abrasives make the most severe scratches at coarse grits.

[TkoK83Spy]

"But Larrins charts say blah blah blah"...glad to see I'm not the only one that feels that way.

Real use, personal use on matter that you cut and your own sharpening experiences are far more telling!

[Larrin]

"But Larrins charts say blah blah blah"...glad to see I'm not the only one that feels that way.

Real use, personal use on matter that you cut and your own sharpening experiences are far more telling!

What charts do I have recommending what grit to sharpen with for different steels?

[Mage7]

I made a post about my experience with grinding a Roadie XL in M398 here:

viewtopic.php?p=1870603&hilit=M398#p1870603

viewtopic.php?p=1870603&hilit=M398#p1870667

viewtopic.php?p=1870603&hilit=M398#p1870797


tl;dr

Started out with Atoma 140. It was unusually hard to grind, but had minimal micro-chipping at 15 dps. Aroma 400 continued to cause microchips, until they were absent off of the Atoma 1200. Afterwards I encountered microchipping with very light cutting tasks--cold medicine blister packs. I added a 20 dps micro-bevel and the edge has been pretty stable but I still encounter microchipping when cutting against a surface.

[BeggarSo]

"But Larrins charts say blah blah blah"...glad to see I'm not the only one that feels that way.

Real use, personal use on matter that you cut and your own sharpening experiences are far more telling!

What charts do I have recommending what grit to sharpen with for different steels?

I would love to see one from you it would be a nice informative write up I am certain.

[vivi]

The problem with that is 99% of the time the use determines the best grit to sharpen with, not the steel.

It'd be like picking your shoes based on which music you're going to drive to rather than your planned activities and the days weather.

[Sharp Guy]

I feel like a lot of these things just get accepted as fact by the knife community but when you dig around there's rarely people with personal experience with them.

I've reprofiled Maxamet pretty low for me (less than 15 dps) and I've never had an issue. I only have one knife with M398 but it's only seen limited use and no need to reprofile yet

[R100]

I was thinking more along the lines of maybe causing chips with too low of a grit.

In all my decades of sharpening I've never come across a steel that chips out when sharpening at low grits (80-200). Whether by hand on diamond plates or on a powered belt sander.

Have you?

I have had this issue with S110V in the LW Manix and Native 5. It made me really dislike S110V but I've come to realise it was because I was using too much pressure. The coarsest grit I use on this steel now is a well worn DMT coarse.

I think for the more brittle steels coarse grit stones need to be used cautiously with very light pressure rather than completely avoided. Apexing with something coarser than 400 grit is something I avoid with S110V and Maxamet but others may have a defter touch.

Dan

[Brock O Lee]

...
I have been able to get away with starting at 150 grit or so but reading about the brittle nature of this steel looking for some advice on where to start maybe 300 Grit? IDK.

Where would you start?

Very hard high-carbide steels like Maxamet does not play well with coarse grits. It leaves a damaged and fractured apex that is not repaired when you eventually finish on finer grits. There are several reports around about this. The workaround was to apex on a higher grit with very light pressure.

...You could try 600 or 300 and see how it goes...

I know there are reports about this. I was just wonderi g if he had personally experienced it.

I've read reports about a lot of things that I've never personally witnessed when it comes to sharpening. X steels chipping out at low grits, carbide tear out, X steel liking a toothy edge, X steel not being able to hold a 30 degree inclusive edge etc.

I feel like a lot of these things just get accepted as fact by the knife community but when you dig around there's rarely people with personal experience with them.

The OP asked a simple question. I gave an answer with a few caveats.

I stand by my post. To back it up, I link the following from Science Of Sharp. It shows sub-surface damage of cracked vanadium carbides in K390 at the apex, sharpened with a coarse stone (DMT Coarse = 325 grit).

Cracks are due to the flexing of the burr (even a small burr). In general, the coarser the stone the larger the burr. Also, the coarser the stone the deeper the sub-surface damage.

His conclusion: "...the cracked carbides will likely reduce its wear resistance. This is also likely one mechanism by which microchips form."

The point is, grit size matters at the apex for these very high carbide steels. To claim otherwise is ignorance.

Carbides in K390.
https://scienceofsharp.com/2021/09/14/carbides-in-k390/

Coarser grits causes deeper sub-surface damage than finer grits.
https://scienceofsharp.com/2019/10/02/g ... ge-part-1/

I agree that there is value in subjective experience. However just because I haven’t seen something does not mean that it does not exist. To be well-informed I should also ground my experiences in the understanding of the science and the related experimental evidence. Together they form the complete picture.

We all learn from each other. We do not have to individually reinvent the wheel. Use it, don't use it.

[vivi]

Ok, well I was still asking him if he had personally experienced it.