180 grit mirror polish

[bodog]

WTF is going on?

I normally use congress ruby(alox) and moldmasters (SiC) stones or cheap chinese stones. They usually work well. I've sharpened S110V at 59 RC. I've sharpened 52100 at 64 +/- RC. I've sharpened a lot of different steels and both work about the same.

The Chinese stones glaze a little faster but with water or oil they work fine. They wear just a little faster and cut a little faster than the Congress stones, normally.

I have sharpened vanadis 4E at 61 RC with both sets with no trouble.

I now have a cpm 4V blade at 62-63 RC I'm trying to sharpen. I am able to cut it with the Congress ruby stones at 220 grit, albeit slowly.

I swapped to a 180 grit chinese stone to work it a little faster. The stone is barely taking any metal off. But here's the deal. The 180 grit is leaving a close to mirror finish. 180 grit.

I scrubbed the stone, resoaked it, and tried again. Basically the same thing happened again. It feels like it's skating on the edge. The Congress stones feels like it's doing the same but a little less and leaving what I'd consider to be a normal 220 grit finish.

With Vanadis 4E being so close to 4V and them having very similar Rockwell hardness, why is 4V acting this way with stones that readily cut the vanadis steel?

I don't believe it's overly hard, the other day I was beating the 4V knife through nails and metal pallet straps with barely any chipping (about .016" behind the edge). If it wasn't tempered (leaving it at full hardness) I would have broken the knife because I was beating it so hard with a hammer.

I worked the surface of the adaee stone with the 220 grit ruby stone and no change. Scrubbed the surface with scotchbrite and dish soap under hot water. The normal stuff. No difference.

I assume the Chinese and ruby stones are both alox so I don't ever consider them to be fast cutters but when used on most knives I've sharpened they've gotten the job done, leading me to suspect something is going on with the steel.

Any ideas?

 

[bucketstove]

WTF is going on?
... 4V blade at 62-63 RC ... 180 grit chinese stone to work it a little faster. The stone is barely taking any metal off. But here's the deal. The 180 grit is leaving a close to mirror finish. 180 grit.
I scrubbed the stone, resoaked it, and tried again. ...
...
I worked the surface of the adaee stone with the 220 grit ruby stone and no change. Scrubbed the surface with scotchbrite and dish soap under hot water. The normal stuff. No difference.
...
Any ideas?

sounds like glazed / worn / dull stone, its not cutting anymore, its burnishing,
it needs conditioning,
to condition a stone you need coarser grit / lower grit,
so your 180 grit stone needs a light 5-10 second rub with plenty of water on 150 grit sandpaper
or 120 grit sandpaper
... or you can also use a nail or a rock to scratch a grid and raise a little slurry

then try sharpening again with oil

it should start cutting again

the curious thing will be how fast it stops cutting and starts burnishing again
(how easy is it to grind the cpm4v steel)

 

[BluntCut MetalWorks]

It's a stalemate between your 4v blade & chinese sharpening stone - burnished close to mirror each other If you gently sharpen Van4E blade against this or similar stone (abrasive + binding strength + etc), you would end up with polishing too. Sharpening stone effective heavily depend on blade carbide shielding and matrix strength (resisting to penetration). In this case, AlO instantly dulls by carbide shield, so abrasive failed to digging deep enough to grab hold of carbide+matrix to plough them away.

 

[bodog]

It's a stalemate between your 4v blade & chinese sharpening stone - burnished close to mirror each other If you gently sharpen Van4E blade against this or similar stone (abrasive + binding strength + etc), you would end up with polishing too. Sharpening stone effective heavily depend on blade carbide shielding and matrix strength (resisting to penetration). In this case, AlO instantly dulls by carbide shield, so abrasive failed to digging deep enough to grab hold of carbide+matrix to plough them away.

I just sharpened an S30V and a 1095 knife yesterday. Seemed to working fine. They were softer than this knife. You think that has something to do with it? It felt like it was cutting into the other steel normally. It was almost immediate that it started skating the 4V.

 

[BluntCut MetalWorks]

Cementite in 1095 is no match of AlO ceramic, so carbide shield is not applicable. Need higher pressure strokes to effectively abrade 65+rc 1095, especially at coarse grit.

S30V MC shielded quite a bit but matrix doesn't resisted enough(not as hard as 4v) so AlO penetrated and plough taken placed. If s30V has similar hardness, then yeah sharpening behavior will be similar as your 4v.

Low grade AlO (usually grey in color) is easily fracture (high friability), so easily end up with a flat top(burnish after) or fluff off(a muddy lapper). Mid grade AlO(alumina - usually white color) usually hold up well to around 1K grit. Red AlO (high temp ceramic) has hardness close to brown/black SiC, of course lower friable but will handle higher pressure, in turn abrade harder material.

It's no joy try to sharpen my 64+rc aebl knives using my cheap AlO stones. White lumina waterstone does well, grey alumina(king ws) easily glaze - unless I whip up a bunch of mud to add lapping action then it work so so (still sucks).

I just sharpened an S30V and a 1095 knife yesterday. Seemed to working fine. They were softer than this knife. You think that has something to do with it? It felt like it was cutting into the other steel normally. It was almost immediate that it started skating the 4V.

 

[jamiesaun]

Sounds like a similar problem I had sharpening a titanium blade one time. It just wouldn't cut that thing. I finally gave up and told the guy to quit buying titanium blades. It's a good metal for a lot of different tasks. But knife blades...not so much.

 

[Noctis3880]

Sounds like a similar problem I had sharpening a titanium blade one time. It just wouldn't cut that thing. I finally gave up and told the guy to quit buying titanium blades. It's a good metal for a lot of different tasks. But knife blades...not so much.

Isn't titanium technically softer on the Rockwell scale than steel is?

 

[bodog]

Cementite in 1095 is no match of AlO ceramic, so carbide shield is not applicable. Need higher pressure strokes to effectively abrade 65+rc 1095, especially at coarse grit.

S30V MC shielded quite a bit but matrix doesn't resisted enough(not as hard as 4v) so AlO penetrated and plough taken placed. If s30V has similar hardness, then yeah sharpening behavior will be similar as your 4v.

Low grade AlO (usually grey in color) is easily fracture (high friability), so easily end up with a flat top(burnish after) or fluff off(a muddy lapper). Mid grade AlO(alumina - usually white color) usually hold up well to around 1K grit. Red AlO (high temp ceramic) has hardness close to brown/black SiC, of course lower friable but will handle higher pressure, in turn abrade harder material.

It's no joy try to sharpen my 64+rc aebl knives using my cheap AlO stones. White lumina waterstone does well, grey alumina(king ws) easily glaze - unless I whip up a bunch of mud to add lapping action then it work so so (still sucks).

The ones I have are a red clay looking stone. I doubt they're high grade because of where they come from and how much they cost but they've handled everything I've thrown at them up until now. But it's also the first time I've thrown a high wear resistance, high hardness steel at them, too. My sic stones don't like the steel very much, either. I guess it'd help if the edge was thinner.

I have a rex 121 blade at 68 rc coming. I'm gonna have to figure something out.

 

[Noctis3880]

Just get a set of DMT diamond plates.

 

[BluntCut MetalWorks]

Norton SiC fine side should gives you 2K finish on the Rex121. Bear down on it, otherwise a boat full of VC would polish the stone. I found 80-120 xstiff ceramic belt will yield 600 to 1K finish depend on belt speed - LOL on a 1.5+hp 2x72 grinder of course.

Having too much fun, aren't you!

The ones I have are a red clay looking stone. I doubt they're high grade because of where they come from and how much they cost but they've handled everything I've thrown at them up until now. But it's also the first time I've thrown a high wear resistance, high hardness steel at them, too. My sic stones don't like the steel very much, either. I guess it'd help if the edge was thinner.

I have a rex 121 blade at 68 rc coming. I'm gonna have to figure something out.

edit: Diamond plates will work very well for sharpening. However, it won't take much to dull diamond, especially when try to thin a rex121 blade grind. To be clear - bodog is playing with blades not knives

 

[jamiesaun]

Isn't titanium technically softer on the Rockwell scale than steel is?

Yes it is. But it's way tougher. At least that's the way I understand it.

Not too sure, I just know my medium Arkansans cuts any steel I've tried so far,, but took forever to sharpen that titanium. Actually it never really did get all that sharp before I just gave up.

 

[Obsessed with Edges]

I just sharpened an S30V and a 1095 knife yesterday. Seemed to working fine. They were softer than this knife. You think that has something to do with it? It felt like it was cutting into the other steel normally. It was almost immediate that it started skating the 4V.

The S30V likely started glazing it; once it starts, it's a very fast slide downhill from there. I killed two essentially 'new' Lansky AlOx hones (XC, C) on S30V attempting a rebevel job; they dished & glazed over and would no longer cut anything afterward. That was my introduction to the meaning of 'abrasion resistant' carbides, and how they relate and respond to certain abrasives; it was a lesson that stuck. Even with less-hard abrasives, like AlOx, that do OK for a while in scooping out harder carbides from the steel matrix, eventually the harder carbides will wear the stone more than the other way around.


David

 

[bodog]

Norton SiC fine side should gives you 2K finish on the Rex121. Bear down on it, otherwise a boat full of VC would polish the stone. I found 80-120 xstiff ceramic belt will yield 600 to 1K finish depend on belt speed - LOL on a 1.5+hp 2x72 grinder of course.

Having too much fun, aren't you!


edit: Diamond plates will work very well for sharpening. However, it won't take much to dull diamond, especially when try to thin a rex121 blade grind. To be clear - bodog is playing with blades not knives

It's definitely more of a challenge with the steels heat treated for high performance. There's definitely a learning curve.

It's much more fun dulling the knives!


Anywho, I've always been one to try to just let the stone do the cutting but I may have to start putting some real pressure on them. I've always been a little worried that it'll stress the edge degrading performance.

 

[BluntCut MetalWorks]

Is plowing a key reason for using 180grit (~70um abrasive)? Well, a 180grit stone won't plow matrix+carbide of high alloy+rc steels with light pressure. But high pressure would dull/destroy diamond, so 'let the stone do the cutting' slowly... very lowly, to preserve diamond sharpness. But ironically, you are not really using light pressure because there are less contact points at coarse grit compare to say 10um abrasive, for simplicity say - 7 to 1 linear density differences, which equal to 49 times higher pressure at 70um compare to 10um. (1). your coarse diamond probably dull relative to freshly fractured/shipped. (2). Are you plowing or slowly abrading carbides away?

To find out (1) - try to abrade a solid stick of WC with 'let the stone do the cutting'. No swarf (no black powder) = dull diamond.

Easily avoid 'stress the edge' by using appropriate size and high-sharpness abrasive to abrade/shape (don't plow here) the apex.

...

Anywho, I've always been one to try to just let the stone do the cutting but I may have to start putting some real pressure on them. I've always been a little worried that it'll stress the edge degrading performance.

 

[bodog]

Is plowing a key reason for using 180grit (~70um abrasive)? Well, a 180grit stone won't plow matrix+carbide of high alloy+rc steels with light pressure. But high pressure would dull/destroy diamond, so 'let the stone do the cutting' slowly... very lowly, to preserve diamond sharpness. But ironically, you are not really using light pressure because there are less contact points at coarse grit compare to say 10um abrasive, for simplicity say - 7 to 1 linear density differences, which equal to 49 times higher pressure at 70um compare to 10um. (1). your coarse diamond probably dull relative to freshly fractured/shipped. (2). Are you plowing or slowly abrading carbides away?

To find out (1) - try to abrade a solid stick of WC with 'let the stone do the cutting'. No swarf (no black powder) = dull diamond.

Easily avoid 'stress the edge' by using appropriate size and high-sharpness abrasive to abrade/shape (don't plow here) the apex.

So polycrystalline diamonds or cbn.

 

[fsatsil]

I would try one of the inexpensive diamond stones for the EP like one of these....
1-ChefKnivestoGo 140grit diamond
2-Ruixin Pro 200grit diamond

 

[BluntCut MetalWorks]

For plowing - beside powerful belt grinder, I recommend: Town Food Equipment (49012) - Large Carbide Sharpening Stone. The fine side will glaze up by high rc + alloy but easy remedy by doping with green SiC powder.

For abrading - beside belt grinder, I prefer fine side of the same SiC stone above - as it and dope up with SiC. Shapton Pro/Glass up to 5K.

For touchup - DMT C thru EE (diasharp 8, duosharp 8 and diafold). Sure would like to try Atoma, if given one. A spyderco UF doped with 0.25um diamond powder = sticky 3 fingers.

So polycrystalline diamonds or cbn.

CKTG 140diamond plate is very durable - I own 2, so far with hard uses, only 1 is worn out. I prefer DMT for flatten waterstone but this will do fine since I don't need that flat. I also have a couple block of HF 4 sides cheapo (SE) diamond stone. I shaved a few bald spots on them now

I would try one of the inexpensive diamond stones for the EP like one of these....
1-ChefKnivestoGo 140grit diamond
2-Ruixin Pro 200grit diamond

 

[jpm2]

I gave up using alox stones on high carbide blades in the 80's.

The only 4v I have is the spyderco mule and notice it's more resistant to my SiC and diamond than most other high carbide blades. I would like to know its actual hardness.

If rex121 is anything like my high 60's exotic blades, diamond will be appreciated.