Is k390 overrated?

[Catchadroppimgknife]

Sharpen it??!! Who sharpens it??!!

Actually I so far have just touched it up on my Sharp-Maker and she’s good to go

I really like K390 - for me easy to keep sharp and any patina that occurs makes it look more interesting. (Although I do try to keep them cleaned, dry and oiled)









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[Mrj]

Without derailing this. Is there any chance we can get some Golden knives with same k390 ??? If I remember correctly the Para 3 and PM2 were done a little different. I’d love to get a bodacious or shaman in it.

[VandymanG]

the thought of K390 being overrated immediately makes me question the OP's sharpening methods and materials.

I will admit, my sharpening technique can be a lot better. Is it possible that a very small, undetectable burr on the k390 will initially pop hairs and whittle, but mush over in a few ten feet of cardboard, creating a very dulled edge? I sometimes have problems with the burr not wanting to come off.

Also, sorry if this post is delayed as im still on the probationary period for posting.

Early on I had issues with sharpening when I first joined the forum. I remember creating a wire burr edge on several knives I had and thinking wow these are razor sharp. I couldn’t figure out how the edges were dulling so fast when forum users were able to keep a razor sharp edge. The trolls didn’t help me figure it out. But finally someone suggested that I was probably not knocking the burr off. Turns out they were right.

[VandymanG]

Over rated? No way! I wouldn't call it my favorite, but it's still a great steel. IMO it's a lot like Cruwear but less stainless. I live in Washington State, and it got a patina pretty quick. I don't even carry it that much. Now I just keep a coat of oil on the blade and all is good. No rust to speak of. I agree with some of the other posts that it does well with a more course edge. When I went over 1000 grit it lost it's bite and had a hard time starting a cut. I say anywhere between 400 and 800 grit is where K390 does the best.

I live in Washington state also. I do carry my LeafJumper SE K390 daily. The knife usually gets carried in the fifth pocket which is a mesh pocket on the various Prana hiking pants I like to wear. It often gets soaked in sweat multiple times a day as I work in the yard, go for walks or hikes. I use it in the rain and while near or on the Puget Sound. I’ve had no rust issues. I do keep it oiled and wipe it dry often. I’m letting my knife develop a natural patina but that’s slow progress with the type of oil I use.

[JoviAl]

K390 for me has been generally excellent. I’ve come to prefer it in SE (P4) rather than PE (DF2 Wharncliffe) as the serrations done on CBN rods just keep on cutting and cutting. When I first got my DF2 I put a mirror edge on it and was somewhat underwhelmed by its longevity, but CBN rods then a very gentle but thorough stropping with a bit of diamond loaded tech cord works wonders.

To the OP - have you tried a fixed angle system to eliminate your sharpening technique from the equation (to a greater extent anyway)? I thought I was going crazy with an M398 mule that I just couldn’t get sharp. Turns out something was up with the edge (it was crumbling to sandy dust when I tried to sharpen it) and in the end I abandoned it after a silly amount of stock removal. Since then I’ve sharpened other M398 blades just fine, so there is the very (very very) small chance that maybe you’re having a similar situation. I’d try taking technique out of the loop first though and using a fixed angle system (or just getting sharpened by someone else) to see if that may have been the issue. Also you might not be stropping enough - I find I sometimes have to strop up to ~30 (very light) strokes to deburr my K390. I use 1 or 5 micron diamond pastes on K390 as mother’s mag (which I use at work on H1/2) literally doesn’t cut it.

[Brock O Lee]

I've had my leafjumper in k390 for almost 8 months today and I keep experiencing fairly fast edge wear.

A few questions, if I may?

- how many complete sharpenings have you done on this knife? I.e, full edge rebuilds, not "touching up", or "stropping back" an existing edge?

- when you resharpen from scratch, do you first "cut off" the old fatigued edge? I.e. slice perpendicularly into a ceramic stone, as if to slice it in half. It would then refect light evenly edge-on, and be uniformly dulled. A great non-fatigued foundation for the new edge.

- how large is the burr you raise between grit progressions? Only visible under light, or large enough to see easily with the naked eye?

- when you're done, is the edge able to slice very thin paper cleanly? Like for instance Rizla cigarette rolling paper, with a slow controlled slice, from heel to tip, without hangups? My test for lingering, tiny, invisible aligned burrs. Not a good test for a coarse edge (coarser than 1000 grit).

[LazyOutdoorsman]

To the OP - have you tried a fixed angle system to eliminate your sharpening technique from the equation (to a greater extent anyway)? Also you might not be stropping enough - I find I sometimes have to strop up to ~30 (very light) strokes to deburr my K390. I use 1 or 5 micron diamond pastes on K390 as mother’s mag (which I use at work on H1/2) literally doesn’t cut it.

I've only been doing freehand edges as I don't have a fixed angle system. However, I think I keep a relatively close angle because I mark where the knife spine sits on my finger. For the stropping, perhaps I should start stropping a lot more than 4-5 times per side. I don't strop too much on either side because I've heard that it reduces the edge aggression or something like that. Although, this "advice" was from reddit, so...

I've had my leafjumper in k390 for almost 8 months today and I keep experiencing fairly fast edge wear.

A few questions, if I may?

- how many complete sharpenings have you done on this knife? I.e, full edge rebuilds, not "touching up", or "stropping back" an existing edge?

- when you resharpen from scratch, do you first "cut off" the old fatigued edge? I.e. slice perpendicularly into a ceramic stone, as if to slice it in half. It would then refect light evenly edge-on, and be uniformly dulled. A great non-fatigued foundation for the new edge.

- how large is the burr you raise between grit progressions? Only visible under light, or large enough to see easily with the naked eye?

- when you're done, is the edge able to slice very thin paper cleanly? Like for instance Rizla cigarette rolling paper, with a slow controlled slice, from heel to tip, without hangups? My test for lingering, tiny, invisible aligned burrs.

I got this knife before I knew that I should be doing touchups, so there is a lot of resharpening on coarse diamond stones. When I do resharpen, I did not cut off the apex because I don't want the BTE thickening up too rapidly.

As for the burrs, I typically raise a very small burr, one that is slightly visible under a small light or somewhat detectable with my thumb. When I am done sharpening, the knife would get some small hang-ups, but with no burr visible from a light or a cheap "microscope."

Assuming that the hang-up is from a very small burr, how would I remove it without creating a microbevel?

[JBoone]

mine also rusts, and i also noticed the edge degradation, but keeping it oiled makes all the difference. just tested and still shaves after months in the drawer

I have started oiling my K390 blades for this reason as well (edge degradation via corrosion). I don’t use for food prep so non issue.

[VandymanG]

mine also rusts, and i also noticed the edge degradation, but keeping it oiled makes all the difference. just tested and still shaves after months in the drawer

I have started oiling my K390 blades for this reason as well (edge degradation via corrosion). I don’t use for food prep so non issue.

I use Frog Lube oil. It works long term and is food safe.

[RustyIron]

I use whatever oil is convenient. And sometimes I'll be working on engines, digging holes in the dirt, or on a wilderness adventure, and I'll eat lunch without even washing my hands.

[gk4ever2]

Looking at Larrin's data for high-speed steels, I noticed at least a few are rated "4" for corrosion resistance, including K390, M4 and 15V - I'm guessing in real world use there are probably differences between these three when it comes to resisting rust – has anyone had experience with 2 or all 3 of these regarding corrosion resistance?

I live in SW Ohio where the average humidity is 70%, although in the summer 80-90+% is not unusual, so I usually carry stainless steel knives (and a coated Sig Sauer pistol). I like DLC coated knives, but as some of you pointed out, the all-important edge is uncoated so it is still subject to rusting.

[vivi]

for me k390 seemed a tad more corrosion resistant than m4, but both of them are substantially better than budget carbon steels like 1095, 1075, O1 etc.

[RustyIron]

a few are rated "4" for corrosion resistance, including K390, M4 and 15V - I'm guessing in real world use there are probably differences between these three when it comes to resisting rust – has anyone had experience with 2 or all 3 of these

Yes. There are noticeable differences in their rust/patina resistance.
My K390 knives easily patinate and will develop rust spots if put away dirty.

My 15V knives haven't developed any rust spots. The newer one that I've used a lot more, appears darker in color, but the color is even. It might have started off with a darker-looking color. Regardless, it does not patinate nearly as easily as K390.

I only have one M4. The blade is coated, and I don't use the knife much. It just sits in the drawer, but the sharpened edge shows no signs of rust or patination.

[Ramonade]

Since sharpening questions from other experienced people often tend to cycle and not answer much (on a forum), I would send the knife to someone who claims to have good results with K390 and see how the edge he puts on your knife behaves

[Spyderfreek]

In response to the original post, there's definitely something wrong with the performance you're getting. If you are positive you are completely reaching the apex and properly deburring, there might be something wrong with the heat treat. I have a few years of experience using and sharpening k390 heavily and it shouldn't require a coarse edge as some have suggested. It should have stratospheric edge retention no matter if the edge is toothy or a mirror. It should also be pretty resistant to abusive tasks like cardboard, hitting staples or hard stuff etc.

[Jimandchris2]

I've had my leafjumper in k390 for almost 8 months today and I keep experiencing fairly fast edge wear.

How I'm pretty certain that the edge is good:
→ I've only sharpened it freehand on either 325/400 to 600/1200 grit on both plated and resin bonded diamond stones at 15 dps. I would do my best at removing the burr by feeling for it and checking the edge with a microscope and light. I would then strop with alternating passes on a 1µm diamond strop on firm leather for about 4-5 times on both sides. This would almost always result in a hair whittling edge.
→ I also ground down a bit of metal over time, surely removing any burnt/fatigued metal. (the heel is currently 0.020" thick)
→ I was using sharpie on my thumb and pointer finger to keep the angle consistent

How bad the performance was:
→ When I first got the knife, I put my own 600 grit edge on it and cut up about 150' of cardboard. The edge afterwards was so worn, it wouldn't even initiate a slice into printer paper, even after cleaning the edge with alcohol and dragging it on wood to remove any debris blocking the edge. It was as if I dragged it across a brick a few times.
→ Another instance is when I cut no more than 60' of cardboard in 1 week. The cutting consisted of mostly thin cardboard food boxes and thin sheet plastic/mailing boxes. By the end of the week, it could not cut printer paper without significantly tearing or creating a super "fluffy" cut.
→ Even if the edge was never used, the aggression would fade over time
* Something that I think should be noted is that I live a few minutes away from the Gulf in Florida. Also, the humidity here can be anywhere between 55-95% in the warmer months.

How I'm pretty sure my expectations aren't too unreasonable:
This is kind of unrelated to the original post, but I recently got a lw manix 2 in 15v a few days ago. I've decided to use the factory edge (which still has a little bit of burr left) and tried cutting up a lot more stuff and being slightly careless such as making contact with glass jars. The edge is still toothy and sharp and cuts printer paper cleanly.
Edit: the geometry of my 15v manix is 0.025" bte at approximately 20°dps

Thanks for reading my ramblings. Does anyone else have a similar experience with k390? Or am I doing something wrong

While your heel is 0.020" BTE, if the edge geometry varies along the blade (e.g., thicker near the tip), it could affect cutting performance on denser materials like cardboard. Check the BTE thickness at multiple points with calipers. Strop it.

[VandymanG]

Definitely odd. I’ve never be super careful when sharpening, I’m very meticulous about it though. I don’t use a sharpening system that fixes the blade in place. I use the Sharpmaker for all my sharpening. That being said I haven’t had to sharpen my LeafJumper SE K390 as of yet. It’s been razor sharp since I got it and I use it daily. Holds an incredible edge. I’m stumped. Might be the heat treat might be very uneven bevels. Maybe ask some of the experts to post recommended links? I’d read anything that is posted about sharpening in the sharpening thread of this forum and maybe ask in the SE thread posted at the top of the forum page.

I think I remember a video by @vivi on sharpening serrated edges if that helps. Or anything @Deadboxheroe might post could help. The forum has a lot of great experts but they don’t always check in or read every link so sometimes linking their user name helps.

[LazyOutdoorsman]

Im gonna update the original post of the heel measurements.
The updated heel specs are 0.020" bte average (0.019" and 0.021"). The average dps is actually 17.42°(16.99°and 17.85°) I know 17.42 dps is a quite a bit less than 15 in terms of edge retention, but it shouldn't be so black and white that it's the difference between "cutting forever" and being out cut by just about anything.'

As for the tip area, its atrocious. At around 0.024" bte on both sides with an average dps of 19.7 (25.38 and 14.01), it needs a lot of regrinding and sharpening improvement on my end.

With that said, I start cutting paper at the heel, which is ok in terms of geometry. I don't think I realized how bad the geometry is on the tip because I wouldn't make it to there after cutting some stuff up.

[Brock O Lee]

Yes those angles are quite obtuse for cardboard. You’ll see a big improvement in cutting ability, and edge retention when you drop to 15 dps. K390 can handle that.

I still suggest you to cut off the old edge before setting the new bevel.

K390 in my experience with household recycling lasts me 2-3 months before I have to resharpen. My cue to resharpen is when it stops to slice cardboard cleanly.

This is on a relatively refined edge, 15 dps, 1000 grit diamonds, no micro bevel, except to deburr with 1 micron diamond spray (on a firm substrate like basswood).

A coarser edge should last even longer on cardboard, but I like it a bit more refined for hard plastics etc.

You may need a few edges to see the performance stabilise. Check out Outpost76 on YT for context.

[LazyOutdoorsman]

Yes those angles are quite obtuse for cardboard. You’ll see a big improvement in cutting ability, and edge retention when you drop to 15 dps. K390 can handle that.

I still suggest you to cut off the old edge before setting the new bevel.

K390 in my experience with household recycling lasts me 2-3 months before I have to resharpen. My cue to resharpen is when it stops to slice cardboard cleanly.

This is on a relatively refined edge, 15 dps, 1000 grit diamonds, no micro bevel, except to deburr with 1 micron diamond spray (on a firm substrate like basswood).

A coarser edge should last even longer on cardboard, but I like it a bit more refined for hard plastics etc.

You may need a few edges to see the performance stabilise. Check out Outpost76 on YT for context.

Thank you. Ima reprofile the next time I can. Also, I think I got better at removing the micro burr, so fingers crossed I can get this knife to cut as long as everyone says k390 can.