Got the scope out again.

[SliceOfLife]

Adjusted to be same magnification via FOV. Obviously the resolution isn't there at 5k optical mag, but the difference is so ridiculous you don't need resolution to see it.

Both images have an ~24micron FOV.


Not trying to be a dick about this, but his edges are horrible. The fact that he didn't suspect he was doing something wrong is hard to believe.

 

[eKretz]

Not sure what I'm supposed to be seeing there...

I don't know what to say, but I don't agree with a lot of that. There's no way in heck that the razor is hitting below the diamond and contacting the nickel plating IMO. And I've tried the experiment myself with the very worn DMT325 and got a DFS that was damn near a very comfortable shave.

 

[SliceOfLife]

You're seeing gaps in his edges that are large enough to visible under a 30x loupe, but are plainly not present at 400x in my edges. This is a pretty big discrepancy.


Get your 325 out. Get a loupe. Look at it. Then tell me you still don't think the razor touches the surface of the plate. It's kind of insane to believe the razor rides on the surface of the diamonds with any amount of downward pressure unless you've simply never looked at the surface of a diamond plate under magnification and wildly overestimate the density of the diamond surfacing.


Here is a 4 micron key on his image overlayed with a 4 micron key on my image with the keys matched. These images are the exact same magnification. (Clipped about 60% of my images borders off for sizing). The edge on mine should mimic the edge on his... unless he's doing something very, very wrong.

 

[SliceOfLife]

What was the last hone to touch the razor before the 325 when you did this test?

Now the razor can ride on the diamonds if you don't use any pressure. It'll be a laughably inefficient cutter in this case, but the <600 grit DMT's aren't great cutters for razors anyway. So it's not impossible to get a shaveable edge off the 325. It's no harder than getting a shaveable edge off a coarse india, or washita, or almost anything that doesn't cut very aggressively without the appropriate pressure. You're not completely off base when you say that larger diamonds take more force to penetrate the steel, that's just reasonable. A DMT 220 (and even 325) do almost no cutting with no pressure added. The 8k chugs along happy as a clam if you don't let the razor skip. The 1.2k and 600 can go either way but like a bit of pressure for best results. You're taking a reasonable understanding of function and extending it to the absurd. The belief that the diamonds get too large to cut steel cleanly is baseless. The belief that Diamonds can cause edge damage through metal fatigue (which by your own logic should be a greater problem on coarser plates where he doesn't see any evidence of this and in fact gets miraculous 325grit shaving edges) is grasping for an explanation to damage much easier explained by user error.

I'd be surprised if you or he would be capable of taking an unbeveled razor (truly unbeveled, not glass dulled), and bevel it to a shave you'd be able to bear on exclusively a 325DMT... but taking a finished razor onto a 325 and not completely ruining the edge? Sure. Taking a 4k or 8k refined razor and managing a little edge thinning without banging it up too horribly, enough to get it to shave? With a little luck, it could be done. You could do the same thing on the 8k with a bit more care. The 1.2k is pretty insanely aggressive even with minimal pressure, it'd be tricky, but I wouldn't rule it out. The thing is, when you're honing with the aim to avoid removing material, rather than to remove material, you're getting into a rather silly region where any hone can be a finisher, provided the right circumstances or sufficient user skill. That's where you see guys insisting their greasy carborundum they bought at a flea market is a Thuri because they can shave off it.

 

[eKretz]

The razor I finished on the 325 got bread-knifed before I finished it with the 325. The edge was definitely all DMT325. I am sure that on a brand new diamond plate the diamonds are sharp enough to let them take a good bite and possibly get down there to the nickel plating, but once they dull to where my 325 is, there's no way. I've tried the same "trick" with several other coarse stones, none got anywhere near the edge that the DMT did, by a long shot. The fatigue doesn't result in instant edge failure, that's not how it works. It merely causes the edge to fail faster. The 325 edge I shaved with failed after several shaves.

 

[eKretz]

Also, I'm not sure his 8k plate was broken in enough. That's the one you have posted comparison images of, right? He mentioned it was only used for something like an hour. It's not likely to have gotten to the point that it should be for best finishing with that little use IMO. Yours probably has had hundreds of hours use, eh?

 

[SliceOfLife]

Thousands. But it was finishing like this from the get go. Maybe he has a defective plate, but I really suspect he simply hasn't learned how to use the 8k... if he's only used it an hour. Diamond plates don't cut like most whetstones. Leaning into it and then easing off as he describes his technique simply doesn't work the way it does on whetstones, because with too little pressure the razor skips and tends to put a wave in the edge, too much and the edge foils or wires and breaks off. I've seen edges exactly like his off the 8k when I got frustrated with a badly warped or misground razor and used extremely excessive (like 500% or more) pressure on it, which is why I suspect it's his error and not a defective plate. It happens more often on the 600 though, as I do use that one for grinding more often and have many many times gotten overzealous and ground a seriously toothy edge into a razor while trying to remove material.

Using the 1.2k and 8k plates you don't really vary pressure at all. You can dig in on coarser plates to grind, but honestly it doesn't really increase speed beyond a certain point (because as I said, you bottom out relatively quickly and are just increasing your pressure into the plate, not into the diamonds), and just bangs up the edge worse. This is roughly testable by doing a few seconds honing with as much pressure as you like and then with normal pressure and comparing swarf production. It will have little difference, or even favor the correct amount of pressure. What this pressure MAY do is damage the plate (DMT has advised many years ago not to use excessive pressure on their plates because it's not helpful or necessary), as you can actually affect the nickle surfacing with a sufficiently small tool and enough downward pressure, take an icepick to a DMT and stab it into the plate a few times to see just how impossible it is to touch the surface past the diamonds.

I'd suggest you take out your 1k chosera or king. Bevel on that, completely. Do at least 5-10 minutes work on one of those stones. Then go right to the 325 and see if you can produce a great shaving edge. I'd be very surprised if you can.


If metal fatigue is pushing up edge failure to the extent you describe, then post shave the edge should show the edge folded over to the extent you theorize happens during honing, as the edge will be more and more prone to this deformation as it nears failure. You should take a razor with this finish to the scope post shave and pre strop and see if this is the case.

 

[SliceOfLife]

Here's a DMT 8k edge honing with excessive pressure, like someone who has never used a DMT 8k would hone. Where have I seen this edge before?

 

[SliceOfLife]

220 using same excessive pressure (325 is at work). Shaves arm hair just fine, but I sure as hell wouldn't put it to my face. Edge is in the same ballpark as the really really bad barbers hones I've tested. Cuts hair about as well as a 1-2k finish I'd suppose. The plate cuts slower than the 600 and probably no faster than the 1.2k, though; so kind of a pointless comparison. Yeah, the diamonds cut shallow even if you go insane with pressure because there's a steel plate behind them and only 20% or so of their radius is exposed. This probably does make the edge on the thin side for 220 grit. That's great. The plate isn't fast enough on razors I'd really care, to be honest. Is it possible to get a shaving edge off it? Sure. I won't rule that out. I doubt it's as good as he claims or you remember, but you could probably cut a beard off with it. Doesn't really matter, since the plate is not suited for that work. I could get a better edge off another stone faster. Maybe his 220grit results are accurate. I doubt it. I expect he probably stepped down to the 220 and did very little work on it, but I may be wrong. I do know beyond any doubt that his 8k and 1.2k results are not accurate. He damaged the razor through poor honing on the plates.

 

[eKretz]

According to the accompanying text on the page with the images the maximum pressure used was less than a pound - I believe it was written as a "few hundred grams." I wouldn't call that excessive personally, and I know he has tried this more than one time as well. I guess we will just have to chalk it up as you have a different theory as to what is going on at the edge with diamond plates.

As regards the fatigue, yes the edge fails. It doesn't fold, it breaks away. The icepick analogy doesn't hold any water (haha) - the reason that the surface of the plate doesn't get touched with razor honing is because of the surface area; of course point contact can touch the nickel plate. With as many points of contact as there are with the razor bevel and spine touching the hone, one would have to apply immense pressure to get all those diamond points to penetrate the steel far enough to allow the steel to contact the nickel plate. In reality the razor is skating on the tips of the diamond particles and they barely penetrate. The leading edge probably catches the edges of the leading particles somewhat more than the rest. With a knife and much less surface area in contact at one time, or even a razor with a pretty hefty smile this would be within the realm of possibility.

 

[SliceOfLife]

The contact area of a standard full hollow ground razor without much wear can easily be less than a cm squared. On a DMT 325, I'd say you can at most expect 20% of that area to contact diamonds at any given time.

You're wildly overestimating the amount of resistance the diamonds offer towards increasing their depth with honing. You also seem to presume that the diamonds penetrate the steel and retain the depth of penetration or somehow further diamonds adjust the razor upwards sufficiently to prevent it from moving towards the plate during the stroke regardless of downward pressure (implying that the steel is able to resist abrasion to such a degree as to overwhelm any users downward pressure and prevent cutting). If this were the case, the diamonds would be wildly ineffectual cutters. Rather, with continual downward pressure, the diamonds will continually deepen their cuts until you are inevitably in contact with the plate. This is the nature of the process. If the razor in fact skated on the surface as you believe, DMT's would be ludicrously slow cutters. They aren't. They're insanely fast. Why? Because the diamonds can and do penetrate the steel to the full extent of their exposure from the plate. Since they are not free, they are far more effective at fully penetrating the steel compared to a medium where the abrasive can be freed, since forward pressure is applied just as effectively at creating penetration as downward pressure. In fact, only by carefully limiting downward pressure and matching the amount of resistance the diamonds DO offer, can you prevent driving into the plate. This is part of the "feedback" you must learn to effectively use DMT's at higher grits. A DMT 8k hones like crap if you let the razor ride on the diamonds. It also hones like crap if you grind the razor edge against the bottom of the plate. The skill required to hone on one is almost entirely based around managing the level of penetration you allow the diamonds to make.


Why do you think you do not dig an arkansas into the DMT or use a high grit DMT when lapping the arkansas? DMT has flat out said because you will put a giant brick of quartz, which has hundreds (thousands?) of times more resistance ((8x2" ark) = 100cm^2 x Quartz vs 1cm^2 x Steel) than a razor into direct contact with the plate, and abrade away the nickle holding the diamonds.

 

[eKretz]

I definitely don't agree with that. Lapping another stone produces slurry, which when ground between the two surfaces will abrade the nickel and remove the diamond. If what you theorize were true, the first time you used a diamond plate with any pressure, all the diamond would be stripped from the plate. Nickel is very soft, and as soon as hardened steel hit it would be removed, stripping all the diamond away with it. The reason they don't want you to use any pressure is because if you use too much pressure, the axial force applied to the diamond by the steel (or whatever) is high enough that the diamond will just be pulled right out of the soft nickel matrix when it grabs the steel. I can't tell you the number of times I've put way more pressure than one is "supposed to" on my DMT325 setting a new bevel on a knife with steeper angles on something like D2 without stripping all the diamond away. (Though certainly the weaker bonds have been broken). I guess we may as well call it a day on this though, as we don't seem to be making any headway.

 

[eKretz]

BTW, the only scars in the nickel of my DMT325 are from a breadknifing. No other marks in the nickel plate anywhere. Same for my Atoma plates. The only scarring of the nickel plating in any of my diamond plates other than breadknifing is from stone lapping when I let too much slurry build up. The only exception is the 8k, which isn't surprising.

 

[Brooksie967]

Interesting stuff. I like to think that Todd is doing enough 'control' testing that he can figure out 'how to use' a DMT 'properly'. The debate here has been interesting but it's way too above and beyond my knowledge to even begin to comment past the fact that the SEM images and cooresponding documentation seem pretty spot on.

 

[SliceOfLife]

Steel is not a rasp by default. Rubbing smooth steel on a nickle surface does not abrade the nickle at an appreciable rate, especially while the steel is not able to apply pressure to the nickle as the diamonds are continually removing the points of steel that are to apply the pressure. You have an inefficient cutter that is in a situation where it can not efficiently apply force. It won't abrade well. The amount of force the steel can apply to the nickle is not enough to strip the nickle, especially since it is almost entirely downward, not forward as with the diamonds. However, the force the nickle applies in return is more than enough to cause this damage to the thin edge which you are attributing to the diamonds. Because the nickle can not cut the steel. The diamonds can. The diamonds "fix" the damage they do to the edge. The surface of the plate does not.

Slurry causes the stripping of diamonds, without any surface in contact with it? Or is the slurry exactly the size to join the nickle and the stone? Because you know as well as I do that a thick layer of slurry will not transfer motion on its surface to abrasion on the base. If that were the case, dilucot would be impossible as a thick layer of slurry being manipulated by the razor on the face of the stone would force massive amounts of autoslurry from the stone. In fact the slurry forms a protective layer on the face of the stone, reducing autoslurry vs using the stone with water, because it minimizes the amount of stress put on the surface of the stone, by allowing the motion of the slurry to distribute force.
Yes, slurry can strip diamonds. It certainly makes things worse, but if slurry were the exclusive cause for the loss of diamonds, then a plate wouldn't last ten seconds of lapping except under water. I've had a plate that has lapped hundreds of stones over the course of nearly ten years, and is only reaching the end of its life now. It was virtually never used under water. For the simple fact that removing the slurry accomplishes almost nothing except reducing the "stiction". It doesn't preserve the life of the diamonds, unless of course you're already pressing the individual particles of slurry into the nickle plating, by pushing the stone too hard into the plate. In which case you'd strip the diamonds almost as effectively without slurry as with it. Slurry "stiction" makes lapping feel less smooth, so when people experience it and also damage their plates, well they extend the logic that the difficulty they faced is responsible for the damage they did. Reasonable, but not factual. The damage is from pushing abrasive into the nickle of the plate. Bound in a stone, or loose in slurry and simply trapped and moved by the stone is nearly irrelevant.

 

[SliceOfLife]

Why don't you test this? Take a balsa strop, and diamond compound. Create the edge damage that this user is seeing, without an unyielding base to drive the razor into.

Prove that the diamonds themselves are able to do this damage to the steel.

 

[Steve56]

Cheers, Steve

 

[SliceOfLife]

Maxxed out DMT C edge XXC to XC to C. Catches and pops HHT after stropping, same for Treetopping. Better performance than some "finishers" people use, for sure. Not shaveable in my book. Yeah, it's pretty amazing for a 325grit edge. Not better than the 8k edge, though. And that's not even shaveable.

Followed it up straight to a Thuringian, with 3-4x the amount of work required to follow the DMT 8k. Stropped and HHT. Lost HHT performance. Translation. The edge off the 325 is a thin and toothy edge, but nowhere near refined to the point of a pre-finisher such as the 8k. His edge radius measurements are an anomaly. Were the radius actually that thin, putting a Thuri polish on it would immediately get HHT to silent falling hairs. Instead, we see that the Thuri is affecting the edge, but rather is struggling to refine an edge that would be more suitable to be taken to a 4-8k stone. Resulting in a step back in performance as the tooth is gradually dulled. Further work on Thuringian could produce a shaveable edge, but already established that edge is significantly less refined than off the 8k. Potentially his hypothesis of the convexing of the edge creates this anomaly. More likely, it is simply an example of a trait being excellent for cutting but detrimental to refinement (the "toothiness" he dismisses for seemingly no reason). An explanation for his edge radius reading could simply be the toothiness itself, allowing a wild variance in edge radius as the edge extends so far from avg towards and away from the spine, creating extremely large edge radii nearer the spine and extremely small ones away from it, while neither accurately represent the condition or performance of the edge.


Put it this way, the variance in the line of the edge perpendicular to the scratch pattern is such that the edge will take a great deal of time to refine on a finisher; which is why it would be suitable to take it to a pre-finisher. At the points of the edge furthest from the spine, the edge may well be thin enough to shave off of, or to take to a finisher, but that is irrelevant due to the condition of the edge where it is recessed nearer to the spine.

 

[eKretz]

The balsa strop wouldn't work for a comparison as it must be used edge trailing. A better idea might be to try the diamond plate edge trailing, which I've suggested in other discussions in the past.

BTW, Todd has told me he has done tests on hundreds of blades with diamond plates, as well as been shaving with straights for a good number of years. I'm pretty sure he has got a decent handle on what's going on.

With all due respect, Todd has already done probably thousands of experiments and tests. What are you basing your deductions on Ian? Much of what you state, you state as though it is ironclad fact. From the beginning, I have made clear that what I'm discussing is theory, but theory that seems to fit what is observed under the scope, based on my own knowledge of working with steel (cutting, grinding, lapping, polishing) for a couple decades and also discussion with Todd, who has certainly pointed out a few things that I missed.

 

[eKretz]

BTW, upon reading back a ways, one comment that stands out as highly inaccurate though is the "steel is not a rasp" statement. You are quite wrong here. Even steel on steel with no lubricant will gall up and scar the hell out of both surfaces very rapidly... "Snouty" surfaces are never really smooth, and it only takes one little spot to cause a high amount of local friction and the two surfaces will almost cold weld together in this tiny spot, and this will cause the material to upset and tear when they are forced past each other - causing more galling and tearing, which just continues to snowball. This occurs with most any material, and the softer of the two is always the one to take the worse beating. This of course does get worse with increasing local pressure.