Sharpening M390?

Razor

Razor

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Dec 8, 1999
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I guess diamonds would be best? I plan on using my sharpmaker with the diamonds rods. Would this work? I plan on not letting it get to dull and just try stropping it with diamond paste on the strop.
 
I have a BM griptillian in 20 CV which is essentially the same steel. I use dmts for everything. Piece of cake. I don't know what you can do with other stones as I never tried. Silicone carbide should work fine though although as I said I never tried. Lately I been using my 600 DMT for my edcs and then stropping on 1 micron cbn on balsa.
 
I've heard it enough...I think I need to run up to Home Depot here real soon and find some Balsa wood. I just gotta know....
 
I use diamonds on my gatco and it’s no problem. I use ceramic on my sharp maker to touch it up. Takes a little but works. I wouldn’t try to profile it with that. I would like to get the diamond rods for sharp maker but haven’t gotten around to it.
 
Sharpmaker diamond or cbn rods to set the bevel, microbevel on brown rods. Profit.

Sharpmaker works great. Use the brown rods to knock down the scratch pattern a little on the main bevel if the finish is too coarse for your preference. The diamond finish slices like a demon though, but you can almost mirror polish if you go up to ultrafine if you prefer smooth push cutting. I prefer a bit of tooth.
 
CPM S-30-V and M-390 both have 4% Vanadium, the Carbides of which are harder than Al2O3 and SiC. If you want to abrade those Carbides, you need either Cubic Boron Nitride or Diamond abrasives.
 
After the diamonds rods, what about touching the edge on the UF rods and not stropping it?
 
The UF rods are Al203. They won’t shine up VC. My finest Diamond stone is 1 micron. Diamond tapes on a platen get finer than that.
 
But doesn't it matter how small the vanadium carbide is? Unless you are at or under the micron size of VC, you're just taking out the matrix and carbides together. I never really go past the brown rods, so I don't even worry about it.

Also watched tests done at 600 grit with diamond and aluminum oxide stones and edge retention was nearly the same.

So at lower grits it doesn't matter what abrasive is used as long as it's harder than the steel matrix, but past a certain point (0.5 micron? How big/small are vanadium carbides?) you want what will cut the carbides.

That's what I gathered when I went down a rabbit hole. I am no expert! Lol
 
soc_monki said:
But doesn't it matter how small the vanadium carbide is? Unless you are at or under the micron size of VC, you're just taking out the matrix and carbides together.
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I understand and agree with this hypothesis, but technically speaking abrasive particles cut chips significantly smaller than their own size so you would want to keep the mean particle size perhaps an order of magnitude larger than the vanadium carbides to assure clean cutting.
 
Mr.Wizard said:
I understand and agree with this hypothesis, but technically speaking abrasive particles cut chips significantly smaller than their own size so you would want to keep the mean particle size perhaps an order of magnitude larger than the vanadium carbides to assure clean cutting.
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Understood. :thumbsup:
 
I am concerned with 3 things: 1) At what point are VC’s being pulled out of the matrix. 2) Is there any possibility that that the VC’s are scratching my finer soft stones. 3) Where do you get reliable information on the relevant sizes of the particles involved. All 3 concerns are obviated by using the harder abrasives. My ability to sleep at night is improved by several orders of magnitude.
 
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In my experience, I’ve never really had to use diamonds for M390 like I would S30V. Now granted, my knives weren’t exactly dull to begin with, but to bring it back to par I’d use a 1k Arkansas stone first and work my way up until I had a decently polished edge. Lately I’ve had good results with the standard stones that came with my Sharpmaker. I don’t think I’d put it to a diamond stone unless I really needed to remove a lot of material because of a chip or something like that.

M390 is probably my favorite “super steel” to sharpen because I’ve had such good results with it.
 
McFeeli said:
In my experience, I’ve never really had to use diamonds for M390 like I would S30V. Now granted, my knives weren’t exactly dull to begin with, but to bring it back to par I’d use a 1k Arkansas stone first and work my way up until I had a decently polished edge. Lately I’ve had good results with the standard stones that came with my Sharpmaker. I don’t think I’d put it to a diamond stone unless I really needed to remove a lot of material because of a chip or something like that.

M390 is probably my favorite “super steel” to sharpen because I’ve had such good results with it.
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The active ingredient in an Arkansas stone is microcrystalline quartz. It is even softer than Aluminum Oxide. In my experience, quartz has a tough time sharpening simple stainless steels much less highly alloyed super stainless steels. I am glad that it works for you although I don’t understand why. I usually sharpen Carbon steels on quartz stones.
 
tiguy7 said:
The active ingredient in an Arkansas stone is microcrystalline quartz. It is even softer than Aluminum Oxide. In my experience, quartz has a tough time sharpening simple stainless steels much less highly alloyed super stainless steels. I am glad that it works for you although I don’t understand why. I usually sharpen Carbon steels on quartz stones.
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I always likened it to being hard enough to clean up the edge without taking a lot of metal off. I’m not sharpening extremely dull knife, just cleaning up the edge. I’d use the Arkansas stone to freshen up the edge instead, probably around the same point someone else would use a strop.
 
tiguy7 said:
The active ingredient in an Arkansas stone is microcrystalline quartz. It is even softer than Aluminum Oxide. In my experience, quartz has a tough time sharpening simple stainless steels much less highly alloyed super stainless steels. I am glad that it works for you although I don’t understand why. I usually sharpen Carbon steels on quartz stones.
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Arkansas stones handle simple stainless with no trouble. I've been doing it for decades.

For the M390 I'd guess it's just burnishing the edge. I'd be cautious about glazing the stones. Been there done that with other steels and don't recommend Arkansas stones for this.
 
McFeeli said:
In my experience, I’ve never really had to use diamonds for M390 like I would S30V. Now granted, my knives weren’t exactly dull to begin with, but to bring it back to par I’d use a 1k Arkansas stone first and work my way up until I had a decently polished edge. Lately I’ve had good results with the standard stones that came with my Sharpmaker. I don’t think I’d put it to a diamond stone unless I really needed to remove a lot of material because of a chip or something like that.

M390 is probably my favorite “super steel” to sharpen because I’ve had such good results with it.
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Its a lot of people's favorite, it doesn't make as much vanadium carbide despite having 4% Vanadium due to the high chromium.
only 2.5% vanadium carbides formed and 17.5% chromium carbides.
Also most companies run it very soft so no one complains about sharpening it but the edge retention is watered down.

I feel there are better steels that kick more butt with more of the finer, harder Vanadium Carbides but the end user can't use soft stones or they won't get the edges as sharp and think it's the steel.
 
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