K390 Chipping, how long till "good steel"?

Seedy Lot said:
Side loading the edge with pruning cuts in the farm and same with weeding woody shrubs with the knife. Not big chips, micro, but happens regularly enough. I could sharpen with more obtuse edge geometry and not have an issue but like the way it cuts with a thinner edge.

The toughness of K390 is on the low side for me and has higher carbide volume than I usually like for edge stability but it is working out well enough. Not hard to sharpen out the micro chips on diamond plates.
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Makes sense. Even the best steels have limitations. I too enjoy how easy K390 is to touch up.
 
oldmanwilly said:
Makes sense. Even the best steels have limitations. I too enjoy how easy K390 is to touch up.
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Yes all steels have limitations and when you exceed the limitations you have failure.

My son has a para 3 in S45VN and he is micro chipping it constantly. I think for him it is when he is carving on wood. I sharpened the edge thicker for him and if he is OK with how it cuts it should hold up better.
 
The only blade steel of any type that I had a chipping problem with was on a Spyderco (several years ago). I had bought two different Native models, one in CPMS30V and one in VG-10 to compare the steels. One of them, I think it was the VG-10, chipped like crazy after field dressing a whitetail deer and then more during normal EDC use. After the second fairly heavy sharpening with a diamond stone Lansky set, the chipping stopped and the steel performed wonderfully.

I theorized that whoever originally sharpened that blade at Spyderco may have overheated it? Hopefully, your K390 will stop chipping after you have a bit of that original steel sharpened away.
 
desmobob said:
The only blade steel of any type that I had a chipping problem with was on a Spyderco (several years ago). I had bought two different Native models, one in CPMS30V and one in VG-10 to compare the steels. One of them, I think it was the VG-10, chipped like crazy after field dressing a whitetail deer and then more during normal EDC use. After the second fairly heavy sharpening with a diamond stone Lansky set, the chipping stopped and the steel performed wonderfully.

I theorized that whoever originally sharpened that blade at Spyderco may have overheated it? Hopefully, your K390 will stop chipping after you have a bit of that original steel sharpened away.
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With your 2 fairly heavy lansky sharpenings you most likely thickened the edge which added more edge stability.
 
"Thickened the edge"?

I didn't change the secondary bevel angle at all. After a couple of good sharpenings, the thickness behind the bevel may have increased a tiny bit, but that has no effect on the edge stability; the secondary bevel angle was unchanged.

if the knife had continued to chip, my next step would have been to increase the bevel angle and/or convex the edge.
 
Seedy Lot said:
With your 2 fairly heavy lansky sharpenings you most likely thickened the edge which added more edge stability.
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Do you not have any experience with factory edges that ran hot, or is it by and large a myth? I've had a similar thing happen with D2 chipping, took a few good sharpenings and now it holds up great (but I did convex it).
 
desmobob said:
"Thickened the edge"?

I didn't change the secondary bevel angle at all. After a couple of good sharpenings, the thickness behind the bevel may have increased a tiny bit, but that has no effect on the edge stability; the secondary bevel angle was unchanged.

if the knife had continued to chip, my next step would have been to increase the bevel angle and/or convex the edge.
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Sorry the Lansky I know the recommended bevels were all a little obtuse.
 
SwissHeritageCo said:
Do you not have any experience with factory edges that ran hot, or is it by and large a myth? I've had a similar thing happen with D2 chipping, took a few good sharpenings and now it holds up great (but I did convex it).
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Maybe and very possible. I have sharpened my K390 knife a decent amount over the last couple years and I still chip it.

I think it can be worse with some steels. I am assuming the K390 is a high temper so has a high hot hardness. Less likely to have a major issue then a lower temepr steel but obviously still possible. I am also assuming that Spyderco nows about edge issues with excessive heat and are trying to mitigate the problems.
 
The geometry being a big factor and exceeding the yield strength is all true. But the interesting thing to me and why I asked the question was the drastic difference in this knife vs my delica in k390 and pm2 in 15v that those two both have been used way more and probably a bit harder than this new endela and those two have had zero chipping. All three are at 30 degrees. So the other 2 have proven that 30 degrees is fine for this class of tool steel for me in my uses at least. If I didn't have that knowledge to go off of I would've probably just sharpened it to 40 degrees and not been too excited about k390.

I'm interested to use it over the next few months and see how it goes.
 
I’m not having any chipping issues with K390 with my normal cutting tasks which includes slicing through chicken bones but I never torque or twist the blade laterally. I always reprofile to a convex edge with 400 grit sandpaper and strop with Beavercraft green compound, nothing fancy but no vestige of the factory edge and all its grind lines left. I’m shocked at how fast this steel wears out abrasives and the Seki City blade smiths most likely are too. All three of mine came with rough spines unlike any other Spyderco I’ve ever possessed and I obtained my first in the late ‘80s. The spines are now smooth and polished.

I realize everyone has different and very valid techniques and uses and my farm working days are long behind me but I reckon K390 would castrate a lot more hogs without touching up than the old Case steel I used in those long ago days. I’m real happy with K390.
 
Lots of great info here presented already but I agree with Seedy on K390 being less likely to have issues with overheating given it's higher tempering temperature. It's much less an issue I'd think than other more finicky alloys like M390 which can have their temper ruined at a much lower temperature than k390.

Not saying it can't happen, it can and I've seen actual test data showing the hardness difference at the edge in steels overheated from the factory from high speed dry grinding, but thankfully Sal Glesser informed me that Spyderco uses flood coolant so that along with the higher tempering temperature of k390 should make this less likely of an issue.

Have you considered applying a micro bevel to your edge? That way you do not have to change the overall angle on the secondary bevel, but you can make the very apex more stable by adding a few degrees per side of a micro bevel. Great way to keep the efficiency of your preferred geometry while lessening the chance of chips starting in the first place. It all depends on how far up these chips are going though. I mean, if they're going well up your edge bevel, it may require a larger microbevel to prevent such damage.
 
Good info on the coolant grinding. It does seem like they've taken steps to prevent an overheated edge. Is the flood coolant used in all factories or just golden? I've used it for roughly a week now since sharpening again and no chips so far. I'm going to try to remember to post back on this after a few more months of use and a good number more edges.

I thought about a microbevel but I've had such good success lately in stropping to make sure I've fully deburred and eliminated burr issues that makes my edges last much longer, well I guess as long as they should've. A microbevel I think would be a royal pain for stropping. It's already difficult enough stropping keeping the angle right with only one main bevel.
 
Mora uses liquid coolant while grinding too and it has been a well known issue from multiple sources that requires sharpening back to get to unaffected steel. I bought a carbon Mora long ago that kinda crumbled along the edge so I tossed it aside, didn’t want to mess with sending back a ten dollar knife but one day picked it up and sharpened it back to a good edge profile and it performed very well. Then I sharpened it again and it was a very durable edge. While I didn’t experience this with every Mora it certainly happened with that one so I don’t believe this is some kind of knife world myth. However lend it the weight you think it deserves. I have not experienced this with any Spyderco but again I never use the factory edge and always reprofile to my own taste.
 
I've had some chipping on my k390 dragonfly but in comparison no chipping on my endura or PM3. I was a bit surprised on the dragonfly. All my edges are 30 Degrees inclusive and polished. It remains my favorite steel
 
IMO, I think there can be considerable variability in Spyderco’s factory heat treatment. The edge on my Rex 45 knife crumbled at 15 Dps and the tip snapped while I was cutting (not prying).

Rex 45 is a hot work tool steel, so you would think that the factory sharpening wouldn’t have a huge effect on the steel temper. All I think we can realistically do is make the edge angle more obtuse until the chipping stops. I would not keep sharpening at the same angle, hoping that the steel will get tougher the deeper you go.
 
K390 Delica:

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She's hit two of those nasty copper plated steel staples while cutting boxes at work and it made me grind my teeth both times. I've probably damaged my teeth worse. Both times showed a slight bright spot on the edge that a few swipes on a ceramic rod corrected. Besides that I've used green sharpal on a leather strop and she still cleanly slices printer paper. I wish the pic showed the bit of patina she has. I may have to buy a cheap light box for better pics.
 
Maximumbob54 said:
... those nasty copper plated steel staples while cutting boxes ...
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I had a small chip on the K390 Stretch after hitting one of those nasty staples. This was not the factory edge (15 dps with a 20 dps micro). It sharpened right out, and I've not noticed chips on any of my K390's since then.





This Endela has the most miles on. It is used to break down several large boxes per week, over more than a year. It also sports a 15 dps edge with 20 dps micro bevel. I typically go 2-3 months between edges, no stropping in-between, before it stops gliding through cardboard.

Top model. Top steel. 👍👍

 
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