Sharpening high hardness and wear resistant steels

bluntcut said:
HH - good ending question and of course insight... LOL - seem that we have been here before with these stuff ;)

btw - I can generate a large visible wire-edge when strop with 0.25um diamond on hard felt or leather. After numerous 'dohs', I threw away those make-shift strops.
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That's interesting to me. I had for a time improvised some diamond based compound at 3 micron using the binder base for my stock compound. It worked well and no issues with burring though not very convenient. I even used it on high density 3 mil poly with no issues, though at times it would flip an existing burr rather than eliminate it - more of an issue of attack angle and weak hinge connection.

The latest version of my Washboard compound has 8 carats diamond per 35 gram (approx) slug in addition to the silicon carbide. I have yet to see it contribute to any burring, even on mild stainless. It helps to have a drop of oil worked on it for best use on budget steels, but that's really to tame it a bit and is optional - still no real evidence of burring. Might be the effect of being in the mix with mostly SiC, though it is enough to work well on high VC. Your S110v featured prominently in the initial testing.

Always more mysteries...
 
steel drake beat me to the punch, this is a chore for nothing less than Sigma Power Select II series… they were designed from the get go to be specific to this application. I will soon have one of bluntcut's 10v paring knives in my kitchen, I will be sharpening it with the SPS II series stones that I have… 240x & 1000x.
 
Here is 10V after 2 minutes edge trailing on 1K waterstone heavily doped with 1200 grit green SiC (hardest type of SiC)

Through the eyepiece - I can clearly see virtually zero carbide shaping (in other word, couldn't find any carbide with clean flat facet). Lumpy protruding objects are carbides - yep there are so many of them.
400x
7rmCc3E.jpg


I wasted a couple 800grit SiC belt in futile attempt to remove some 10V lower grit scratches - each belt belt lasted about 3 revolutions before glass smooth.

Edit to add: Edge after 1 minute sharpen on DMT EF. It looks like a clean abraded surface (a lot of plowing done)
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wnIFGwA.jpg


Smooth bumps are carbides - 1000x reduced 50%
AItiTXd.jpg
 
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You are right, oil reduces friction quite a bit especially when plate is new. Some of my plates are rusted - so oil would be beneficial here as well... ok, I neglect & hard on these plates - yes, most of them stay outdoor under a patio table :)
Maggot Brain said:
You might also consider using oil on your diamond plates, would likely lessen friction and cut deeper more effectively than just water.
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Slightly OT, I have sharpened my HAP40 to face shaving sharp, carried it several days without using, and found out that the edge has dulled and no longer shaved well. Stropped a bit with green (Dialux) on end grain paperboard, and it came back.

Is it dulling due to micro corrosion because of sweat?

Luong, if you can test this on semi stainless such as M4, and look at magnification, perhaps we find the answer?

On Topic:

That clump of carbides on first image, do they the one contribute to the edge wear retention? Makes me wanting BCMW 10V now :D
 
bluntcut said:
You are right, oil reduces friction quite a bit especially when plate is new. Some of my plates are rusted - so oil would be beneficial here as well... ok, I neglect & hard on these plates - yes, most of them stay outdoor under a patio table :)
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It is possible that if your plates are rusted, you are actually using a loaded plate… the rust being from the steel loading it. Have you tried cleaning with a scrub brush and abrasive cleaner?
 
Hi,
Chris "Anagarika";16629768 said:
Slightly OT, I have sharpened my HAP40 to face shaving sharp, carried it several days without using, and found out that the edge has dulled and no longer shaved well. Stropped a bit with green (Dialux) on end grain paperboard, and it came back.

Is it dulling due to micro corrosion because of sweat?

Luong, if you can test this on semi stainless such as M4, and look at magnification, perhaps we find the answer?

On Topic:

That clump of carbides on first image, do they the one contribute to the edge wear retention? Makes me wanting BCMW 10V now :D
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Hi,
It should be easy to confirm or rule out corrosion,
table the knife for a few days, in dry spot, oiled or ...
then check sharpness
if sharpness hasn't changed its probably sweat corrosion
if sharpness has changed its probably metal fatigue
 
Here is my quick/rough calculation on corrosion rate after 4 days on a freshly sharpened hap40 edge. Urban + high ambient humidity (ignore sweat)

Conservative calc.

Corroded thickness(in nm) on edge = (2 facets * (est corrosion thickness per year in urban with high humidity on carbon) * (prorate for hap40 4%cr)) /(365/4) = (2 * 30000 * 0.6) / (365/4) = 438nm

A freshly sharpened apex with radius 300nm (decent shaving). so with this calculation, after 4 days (w/o sweat or P on it), its apex radius now be in 700+nm, which won't shave too well any more.

Stainless steel will also loose some sharpness due to minor thickness increase (due to volume gain) from passivated layer + tiny amt of corrosion to outside facing c&fe.

Yeah 10V ~25% carbide volume is pretty much shielding the matrix from wear. From a perspective of 2x2x2 um cube, effective and conservative shield/coverage rate from abrasion wear: perpendicular/pure-push is 25%; 45* 50%; less than 25* is about 100%. Toothy (micro serrated edge) actually increase the incident of push/perpendicular/pressure force. These kind calculations sort of common sense, once envision how much the matrix face/interact with cutting material. Of course when relevant we need to take into account impact/adhesion/steer/torsion.


Chris "Anagarika";16629768 said:
Slightly OT, I have sharpened my HAP40 to face shaving sharp, carried it several days without using, and found out that the edge has dulled and no longer shaved well. Stropped a bit with green (Dialux) on end grain paperboard, and it came back.

Is it dulling due to micro corrosion because of sweat?

Luong, if you can test this on semi stainless such as M4, and look at magnification, perhaps we find the answer?

On Topic:

That clump of carbides on first image, do they the one contribute to the edge wear retention? Makes me wanting BCMW 10V now :D
Click to expand...
 
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Coat the apex with facial/neck oil to slow down ambient corrosion for non-stainless steels.
Chris "Anagarika";16632144 said:
Luong,

Thanks it explains the VG10 is better after similar treatment. :)
One element why some likes VG10 more, I guess.
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Maggot Brain said:
steel drake beat me to the punch, this is a chore for nothing less than Sigma Power Select II series… they were designed from the get go to be specific to this application. I will soon have one of bluntcut's 10v paring knives in my kitchen, I will be sharpening it with the SPS II series stones that I have… 240x & 1000x.
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The 240 will work ok, you are going to be sadly disappointed with the 1000. Also, dmt is pretty up front about no oil on their plates.

Russ
 
mycough said:
The 240 will work ok, you are going to be sadly disappointed with the 1000. Also, dmt is pretty up front about no oil on their plates.

Russ
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DMT's caution about using oil on the plates is more about making sure they're cleaned properly afterward, which is simple.

If cleaned regularly, DMT plates can be used with oil, and to no harmful effect. It's common sense to clean a diamond hone after use, as they'll be prone to clogging if not cleaned, no matter what is used for wetting them (or even if used dry). They'll clean up easily with dish soap & water after use with mineral oil. It's how I've been using mine, cleaning them after each session. Takes about 5 minutes to wash them up, no matter if they're used dry or with water or oil, and they'll stay as unclogged as when new.

And just enough oil to 'shine' the surface of the hone is all that I've needed. On a 6" or 8" DMT hone, that usually means I deposit enough to make a dime-sized drop on the hone, and spread it around with my fingertip on the surface. Periodically during sharpening, I sometimes wipe the dirty oil away with a microfiber towel and reapply fresh oil, and still using the dish soap & warm water afterward to clean it all up completely.

This is how DMT explains use with oil on their hones, from their FAQ page ( https://www.dmtsharp.com/resources/...er-dry-or-with-water-but-can-i-use-oil-anyway ):
"DMT recommends you use DMT products dry or with water only. Although mineral oil or WD40 will not harm the DMT products, they can impede sharpening if used in excess and can damage the sharpener overtime if not properly cleaned/removed from the sharpener. DMT recommends that you always wipe your Diamond Sharpeners clean and store dry after use. Put away your benchstones dry and store in a dry area. Use leafing (paper towels, cloth, plastic storage bag) in between your bench stones to prevent abrasive sides from rubbing.
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So, if you keep it clean: no damage. If you neglect cleaning it: might be damaged over time. The "if not properly cleaned" wording sounds sort of scary, but it's a piece of cake. Just clean them as you'd clean a dish in the sink after supper, and you'll be fine.


David
 
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mycough said:
The 240 will work ok, you are going to be sadly disappointed with the 1000.

Russ
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Why would he be disappointed with the 1000? As the video I posted in this thread showed, the Sigma Power Select II 1000 had no difficulties in apexing a ceramic knife. By comparison to a ceramic knife, literally any steel is easy to grind. Now granted, if you don't like soft and very muddy waterstones then you probably won't like the SPS II 1k, but if you don't want a highly friable stone for this application then you are pretty much going to be limited to diamond plates as SiC oilstones also tend to be highly friable.
 
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Steel_Drake said:
Why would he be disappointed with the 1000? As the video I posted in this thread showed, the Sigma Power Select II 1000 had no difficulties in apexing a ceramic knife. By comparison to a ceramic knife, literally any steel is trivial to grind. Now granted, if you don't like soft and very muddy waterstones then you probably won't like the SPS II 1k, but if you don't want a highly friable stone for this application then you are pretty much going to be limited to diamond plates as SiC oilstones also tend to be highly friable.
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I'm assuming you listen to cliff stamp a lot otherwise you wouldn't have used the word trivial where "easy" would've sufficed. If there's one truly horrible thing cliff imparted on the knife world, it's the extreme overuse of the word trivial: making otherwise intelligent people sound halfway retarded.
 
If there's one truly horrible thing cliff imparted on the knife world, it's the extreme overuse of the word trivial: making otherwise intelligent people sound halfway retarded.
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Sounds serious.
Wait . . . it sounds trivial . . . but the consequences of doing this trivial thing sounds . . . not so trivial . . . down right horrible.

I'm glad I have no dinosaur in this orgy. Now I know what that means . . . I was wondering before.
 
Good info Dave. Thanks Bodog, darndest thing, the other last few comments I can't read because of the handy, dandy ignore button.
Hopefully no new readers are being led astray, read with care.
Russ
 
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