M390 (and cognates) rolling?

I didn't get to cut quite as much cardboard last night, but I did cut enough to determine that the rolling is most likely caused from stropping. There was a tiny bit of apex deformation, but nothing even close to what I have been getting.

This would also explain why CPM-154, D2, and XHP don't roll. What's confusing, though, is that S35VN hasn't been rolling or deforming, and Elmax has been rolling very little. Odd stuff.
 
dkb45 said:
I didn't get to cut quite as much cardboard last night, but I did cut enough to determine that the rolling is most likely caused from stropping. There was a tiny bit of apex deformation, but nothing even close to what I have been getting.

This would also explain why CPM-154, D2, and XHP don't roll. What's confusing, though, is that S35VN hasn't been rolling or deforming, and Elmax has been rolling very little. Odd stuff.
Click to expand...

There's a growing consensus of opinion among some experienced BF members here, that steels with ~ 3% or lower vanadium don't present as much trouble for refining using abrasives other than diamond or CBN. When the vanadium gets up to ~ 4% or higher (think of S30V as the threshold, at 4% vanadium), that's where issues like this come up.

Just so happens, all the steels you mention above^ are at/below that 3% threshold for vanadium (Elmax & S35VN at 3% vanadium; others mentioned are much lower). Your observations would seem to confirm the 3% vanadium thumbrule. And the M390, 20CV and CTS-204P are at 4% vanadium. Interesting...
 
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I think we identified early in thread--it's the OP's sharpening process combined with these particular steels. I do not believe there's anything wrong with the product HT in the steels from these companies, based on my somewhat limited experience of working with them. As David and also I posted, try 1 knife, sharpen coarse on diamonds without stropping, or strop VERY lightly minimally just a few strokes on diamond or cbn. That will solve your problem. I use knives with lower edges than OP in these steels and do not experience excess rolling.
 
I have this exact same experience with 20CV. After just a few pieces of cardboard, the edge rolls. I sharpen on a KME, 100 grit through the 0.10 micron lapping films at 17 DPS.
 
Again, don't know all your details, but sounds like it could be a similar issue: over-refined/polished edge where the process weakened the matrix of steel + vanadium carbides. I'd suggest a really easy test, just try a different, more basic sharpening progression on 1 knife, where the goal is to create an optimally sharp edge that is tailored for durability under slicing heavy material like cardboard. Create a nice coarse edge on the diamond abrasive of your choice, anywhere from 180 to 400 grit ANSI. Try creating the edge first without stropping at all, just deburr/finish on your stones. This is David Martin's suggestion, and I totally agree that is the best way to start such a test. You start minimal, see if that works, then gradually add back refinement steps/abrasives to your progression, adding back 1 step at a time and testing after each one. Ideally, this would help you identify which step in your progression is the one that causes the rolling to start happening.
 
Obsessed with Edges said:
There's a growing consensus of opinion among some experienced BF members here, that steels with ~ 3% or lower vanadium don't present as much trouble for refining using abrasives other than diamond or CBN. When the vanadium gets up to ~ 4% or higher (think of S30V as the threshold, at 4% vanadium), that's where issues like this come up.

Just so happens, all the steels you mention above^ are at/below that 3% threshold for vanadium (Elmax & S35VN at 3% vanadium; others mentioned are much lower). Your observations would seem to confirm that 3% vanadium thumbrule. And the M390, 20CV and CTS-204P are at 4% vanadium. Interesting...
Click to expand...

Just want to thank you for this comment - what you've said cannot be stressed enough.
Vanadium contents determines whether you can use common abrasives like aluminium oxide or Japanese stones, or should stick with diamonds and CBN.

Mike Brubacher has developed an edge rolling tester, we should get it in a month at Knife Grinders and will carry out a study to get more details about this issue, the Vanadium contents threshold, the abrasives to use etc.
This tester proper name is "Structural Edge Tester".
The below thread on the BESS forum tells how the idea was conceived, and the tester developed:
http://www.bessex.com/forum/showthread.php?tid=240
 
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I do want to take a minute to thank the community for the response, especially Obsessed with Edges. This has been awesome information to have, and finally pushed me to get more sharpening equipment. Learning what steels I like and dislike the properties of is also a great way to save money.
 
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