m390, how bad will it be?

JoshRG

JoshRG

Joined
Apr 24, 2014
Messages
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I've been strongly considering giving m390 a shot but have some reservations before doing so and would love some input from you gents if don't mind. :)

As of now I only use AEB-L and aside from breaking 90's on the edge and a tad bit of surface prep, pretty much everything is ground post heat treat. I imagine this way of doing things will have to change with m390 but just how abrasion resistant will it be post heat treat? Ceramic belts only or will I still be able to use finishing belts (trizact,cork,etc)?

Also, will I have any issues with drilling or cutting on the bandsaw? I believe I've read about other makers saying it was almost impossible to cut the higher vanadium steels on their bandsaws. I don't believe m390 falls into this category but I really do not know.

Thank you in advance for any and all information guys!

Blessings,
Joshua
 
The good thing about M390 is that it grinds and finishes almost as easy as AEB-L but holds an edge almost as long as the higher Vanadium steels that are so hard to finish. Your usual method should work but it may take a tad longer and you wont get quite as much belt life.
 
JoshRG said:
I've been strongly considering giving m390 a shot but have some reservations before doing so and would love some input from you gents if don't mind. :)

As of now I only use AEB-L and aside from breaking 90's on the edge and a tad bit of surface prep, pretty much everything is ground post heat treat. I imagine this way of doing things will have to change with m390 but just how abrasion resistant will it be post heat treat? Ceramic belts only or will I still be able to use finishing belts (trizact,cork,etc)?
Also, will I have any issues with drilling or cutting on the bandsaw? I believe I've read about other makers saying it was almost impossible to cut the higher vanadium steels on their bandsaws. I don't believe m390 falls into this category but I really do not know.

Thank you in advance for any and all information guys!

Blessings,
Joshua
Click to expand...

Maybe you would like to watch this video ...........

 
Darrin Sanders said:
The good thing about M390 is that it grinds and finishes almost as easy as AEB-L but holds an edge almost as long as the higher Vanadium steels that are so hard to finish. Your usual method should work but it may take a tad longer and you wont get quite as much belt life.
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Interesting, that is definitely not what I was expecting. Sounds like good news to me! Thank you for the information btw, really appreciate it!

Blessings,
Joshua
 
Hey Josh, I haven't used M390 but have used 20CV. I did a lot of grinding and finishing before heat treating. Edges down to 0.015" and at least 400 grit on the finish. It made post heat treat sanding less difficult. I found that it was on par with S35VN or N690 in terms of difficulty finishing.
 
Robert Erickson said:
Hey Josh, I haven't used M390 but have used 20CV. I did a lot of grinding and finishing before heat treating. Edges down to 0.015" and at least 400 grit on the finish. It made post heat treat sanding less difficult. I found that it was on par with S35VN or N690 in terms of difficulty finishing.
Click to expand...

Thank you Robert,

I've used N690 and while it was a bit tougher to grind than AEB-L it wasn't horrible. How much more of a headache do you feel it would be to grind from full thickness post heat treat, or do you feel that would be a terrible idea? Thanks again, I appreciate the info brother!

Blessings,
Joshua
 
If it's thin stock maybe 0.07" to 0.09" it probably wouldn't be too bad but thicker than that I wouldn't want to be tackling, personally. The blades I sent to Peter's came back perfectly straight so nothing was lost grinding pre HT. I was glad to not have to grind too much afterward.
Annealed the stuff works like butter so I think you'd save on belts and headaches grinding as much as you can pre HT.
 
Everybody grinds different and thusly they have different ideas about how hard it is to grind hardened steel. I use a LOT of 1/8" 10V and grind all my bevels after H/T. I can take the bevels on a hardened 4" 10V hunter down to ~.020" at the edge with a 60 grit belt in less than 5 minutes. If you turn up your speed, apply some pressure, and make the sparks fly you'll be surprised how fast you can grind a blade.
 
I must be doing something wrong then. I think AEB-L is butter compared to Elmax and it has even less Vanadium. But I haven't tried it fast and wet yet.
 
Hello To everyone,

My name is José and I'm from Barcelona/Spain. Been making small knives (just putting the handles on finished blades) for a while, and decided a bit more than a year ago to start doing some testing with M390...you may think I was totally foolish (no experience in heat treatment at all), I do not blame you...
Got a furnace, Rockwell tester, grinder, etc...and there I went...
Did some different testing on hardening, tempering, sub-zero (dry-ice, LN2), and finally got some nice results...(I bought a bar and 3,5 and 4,5mm thick plates...this steel is far from cheap)

Now on the question asked by Joshua:
- I had no issues in cutting it with a good belt, just be patience, no rush, slow speed and use cooling (the first piece of M390 I got was a bar).
- Same case for drilling...
- Avoid heating the blade as much as you can (in my learning process some of my blades were laser cut...all of them got hardened and had to throw them away -annealing did not work out-), ended up with water jet cutting with very nice results)
- It is a great stainless steel (in comparing with other blades I worked with, it definitely plays in a different league)
- I got reasonable corrosion results with dry-ice, however LN2 is better and long term cheaper. To give you an example, after polishing a blade and trying to etch it with acid, only some part of it got etched after 20' in the acid at room temperature...I always clean the blades before been etched with a special product in a ultrasonic cleaner (hot)
It is definitely a great stainless...

Greetings to all, this is a great forum.
José
 
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I laser cut air hardening steels quite regularly and have never had anything but a perhaps .005 (0.12mm) thick hardened skin at the cut edge to deal with.
 
Well, that's what I was expecting...the 4 blades broke like glass after cutting them...these were 3,5mm thick...
I'm wondering if the guy that adjusted the machine knew what he was doing (this is a respectable company in the industry)...Böhler advised me to avoid laser if possible (after I made the cuts!!)
I have also got to say that they were skeleton blades...maybe it was because of the thin sides...anyway, the thing is that with water jet I have no issues at all (besides the fact that it costs 4 times more!!)

I have learn a few things with M390...and they all sum up in been extremely careful with the entire start-to finish process, and keep the blades cool...I also grind the blades after being hardened
 
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Thanks! encouraging words :thumbsup:
Will keep on working and hopefully improving my technique...(been watching this forum and a lot of videos for a while).
I'm also familiar with special woods, own +50 different species...I love wood.

I work as a business consultant, but always been fascinated with knife making, unfortunately here in Spain is not that popular (my father got me into this when I was a boy...he's 84 and still makes knives)

Will post other pictures

If anyone needs any information on M390, please let me know, will be more than happy to share my experience
 
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Lipo423 said:
If anyone needs any information on M390, please let me know, will be more than happy to share my experience
Click to expand...

Those examples of yours look really nice!

About your M390 heat treatment testing, what was the austenitizing and tempering regimen for the samples that were nitrogen cryo-d and dry ice subzero treated?

Also, did I understand correctly that you found that, compared to the dry iced sample, the nitrogen cryo-d sample had noticeably improved corrosioon resistance with the same aust/temp regimen for both?

Thanks!
 
I followed a kind of "consistent methodic" testing approach, and documented everything (each step followed a Rockwell testing)...with my professional-level of ignorance, but been a process-oriented person I thought it was the best way, and it paid off.
Austenitizing time was 25-30' at 1150 celsius, then cryo, and followed by two temper cycles at 200 celsius.
The final results with the same heat treatment process were better with LN2 (in hardness & corrosion), I find the final product better, in my taste (the final blade can only be sharpened with a carbide stone...and it takes a while...)

The other issue with dry-ice, is that you need a "vehicle" to get the blades homogeneously treated...which is also messier, expensive, and you raise slightly the temperature because of the heat-exchange...just be extremely careful with the blades right after being taken out of the LN2 and get them inside a proper isolated container, so the temperature change is not that dramatical, but slowly balanced
I made this one myself (see attached picture), to avoid potential blade cracks...and it works...no issues so far

I followed Böhler heat treatment instructions, but went for a much deeper cryo treatment to get a higher level of carbides in the blade...
 

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More blade pictures...Macassar Ebony handle.
This is a knife I made to my English friend Dave Hilton (I gentleman who besides been a great guy has got an unlimited knowledge about exotic woods...his passion about them is like a "contagious disease" Thanks Dave!!)
IMG_2557 Low.jpgIMG_2579 low.jpg
 
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