Burrs - SEM imaging - thoughts & theories

[eKretz]

It produces a very smooth edge comparatively actually, as far as I understand it, the theory goes that it's because of the deflection and tiny convex at the edge. It's basically the bevel you envision (nasty and ragged) with a tiny much smoother microbevel that's formed by the deflection and trimming off of the proud surface once the blade is flipped. The continual pushing away of the apex never lets the very apex form these very deep and ragged scratches. Only the very tip of the diamond particle is doing the work because the apex flexes away - so there are no deep scratches cut by the diamond, just basically a light brushing by the polished tip of the abrasive particle.

Without Todd's level of magnification though you'd never even see this, let alone have anyone trying to shave off of one of these coarse plates.

 

[HeavyHanded]

I'm not as daring as others... I would have to see a lot of microscopic evidence before I attempted this! That would seem to produce a very rough shave lol

I have seen evidence elsewhere where the lower you go in angle (on an edge) the more effect the grit has on leaving a ragged edge. So an edge finished at 11 dps on a 325 grit diamond plate would be a ragged edge indeed. There is a reason people have been shaving off of high grit stones for years....

I once managed a pretty good dry shave off of a Mora laminated blade done on an 800 grit King stone and stropped on newspaper - was amazed at how much stubble flew off and how smooth my face felt initially. After about 20 minutes my entire face started itching like mad and turned a nice blush of red. Just cause you can do something doesn't mean you should

 

[eKretz]

Yeah that doesn't seem to have the same mechanism at play though. The very hard abrasive particles with polished tips seems to be key. I had absolutely no razor burn at all, nothing.

 

[ToddS]

I suspect the ability to produce an outstanding shaving edge with a DMT 325 is a bit of an anomaly and really this is just a bit of fun.

This image is from a vintage carbon steel (Genco) razor honed on my DMT325 (note the magnification):

I know from experience (correlating images to shave performance), that this is the perfect edge for me. Ultra-keen with a slight convexity near the apex. After seeing this result, I honed a Gold Dollar razor (medium hardness silver steel) with the same light strokes (more than 100) stropped on clean leather and shaved with it. It was an outstanding shave, ultra close with no irritation. I shaved with it again the next morning and it had lost a subtle amount of keenness, typical of this Gold Dollar - but no evidence that this was a weak edge. I tried to hone the razor again, but had more chipping than the first time (I didn't note which side of the hone I used, maybe one side was better). I eventually managed a nearly chip-free edge, and tried shaving, but abandoned it after the first pass.

I think it is important that Eric and I are using the light strokes typical of straight razor honing - in some sense using the diamond plate incorrectly.
Personally, I couldn't see any evidence of swarf after a few hundred strokes.

I would also note that the edge from my DMT600 was a foil; keen but extending beyond the apex. Interesting because this the first time I have observed a foil-burr in alternating edge leading strokes on a surface other than lapping film. Also interesting is that the edge width became progressively LARGER with increasing grit from 325-600-1200-8000. Again, maybe evidence that this is incorrect use of the DMT plate in that the pressure is too low.

 

[HeavyHanded]

Is it possible the strong initial results from the 320 DMT razor stem from it being already prep'd with finer hones, establishing a much finer geometry. The coarse diamond, even battered to a blockier contact shape, was able to run with it for a honing or two but no further.

 

[ToddS]

Is it possible the strong initial results from the 320 DMT razor stem from it being already prep'd with finer hones, establishing a much finer geometry. The coarse diamond, even battered to a blockier contact shape, was able to run with it for a honing or two but no further.

I think you are exactly right. I took that razor back to the Chosera 1k and then to the DMT coarse with Norton honing oil - the edge looks perfect, not a single microchip.

 

[eKretz]

Definitely seems to be anomalistic. I didn't see any evidence of swarf when finishing either. Here's the thing though. My DMT edge started out as my Atoma edge, so it sure wasn't coming from a much finer finish. I also noticed my edge wasn't nearly as nice at the extremes of the blade (heel and toe) - where it was contacting the diamond plate in less worn areas along the edges. I also started honing with medium pressure with both my Atoma and my DMT to be sure I got rid of all traces of the previous finish. That produced quite a bit of swarf. After switching to finishing strokes with very little pressure then no more was produced. So it may be that this extremely smooth apex is just a burnishing effect and nothing more. It seems the more very light strokes the better, so that would fit I think.