New microscope, different steels, hypotheses?

[RustyIron]

The diamond matrix stones arrived from EdgePro a day early. I needed to try them out right away. First up was some S110V because. I've always been able to get a good edge on this blade, so it was a good place to start comparing stones. You guys suggested that I might have been a little sloppy about moving the blade during sharpening, so I took some extra effort to up my game. I gave the blade a bit of reprofiling on my cheap diamond plates then went at it with the new 650 diamond matrix. The resulting edge was nice, so I upped it to 1100. Much better, so I went to 2300. At this point, the edge was good enough, but I didn't pay good money for the 4k to let it sit in the box. I gotta say, after taking the edge to 4k with these stones, I'm very impressed. The edge is right up there with my best work... and I didn't have to put in any extraordinary effort.

Next was the Maxamet blade that hasn't been easy to work with since I got it. I could never get the edge as sharp as I wanted. Again, I started off with the cheap plates. As has been my experience in the past, these plates really tear up the edge. I think I should have thrown down for the 250 grit diamond matrix stone. There was a small area of the belly where I couldn't get rid of the chipping, so I just moved on to the new stones. I went through he progression as before. When I didn't mention was that I can really feel the edge with these stones. Call it feedback if you will, but it's pretty easy to know what's going on at the edge just from the feel.

Anyway, the new stones left a mirror-like finish on the Maxamet, which was somewhat of a surprise. It's only with the naked eye, though. Under magnification, there are the scratches you'd expect at 4k. The minor chipped area never polished out, but that's ok. I didn't want to hog away a lot of material just for this experiment. Regardless, the edge is substantially sharper than I'd ever before achieved on Maxamet. I'm VERY pleased.

Here's a pic that I took on a whim just using what was on my desk. A picture of the edge under substantial magnification didn't excite me much, so this will have to suffice.

 

[sickpuppy1]

Lol, somehow I knew you’d like em. Yeah, the 250 will take care of the heavy lifting on the chip I would think. For me, once I get to 2300 it is trailing edge strokes only for the best finish, but that’s just me.

 

[Diemaker]

If you use your microscope enough once you reach the apex you will only use edge trailing passes after that. The difference in microchipping between edge leading and edge trailing is quite noticeable.

Until you get the 250, and even once you do, try using almost no pressure, edge trailing passes, and flip the knife back and forth to try to reduce the burr formation from one side to reduce the damage done to the apex by the extra coarse diamond stone. The last suggestion is something I have been thinking of but haven't tried yet. I have noticed under the microscope that the 80 and 250 stones do so much damage to the apex that they are very limited on how keen they can get it, no matter what steel.

 

[RustyIron]

The difference in microchipping between edge leading and edge trailing is quite noticeable.

Y'know, you're probably right. I was being a bit hamfisted and impatient with the coarse one.

I have noticed under the microscope that the 80 and 250 stones do so much damage to the apex that they are very limited on how keen they can get it, no matter what steel.

Thanks. It's encouraging to hear that the problems I run into are not unique, but commonplace. The challenge is learning or figuring out how to mitigate the problems. Now I have some ideas for next time.

 

[eKretz]

When using edge trailing strokes at the end, I find that using as short a stroke as possible really helps to reduce burr formation. So basically, once you have the grind all the way down to the apex make only very short edge trailing strokes and frequently flip the blade. I can usually get very near almost no burr at all this way.

Edge leading on coarser stones does indeed do a lot of damage to the apex. The finer the stones get, the less of this damage that occurs. But it's still there. If you want the absolute finest edge you can get, finish edge trailing, minimize the burr a(hopefully you'll be down to about none at the end) then remove it if necessary.

Todd S. has some good stuff regarding this on his electron microscope blog. Edge trailing can produce a narrower than expected included angle at the very apex sometimes depending on the steel and how acute your angle is to start with. Something like a Suehiro 20k hone will produce almost a perfect geometry even edge leading.

 

[Diemaker]

My comments are specific to the Matrix stones, both post #23 and here. Early in their development, I was seeing random deeper scratches in the bevel with the 2300 and 4k stones. After dressing the stone all would be fine for a few knives then the random scratches would reappear. Even though the stones were still cutting fine I would have to dress them to get rid of the random scratches. Under the microscope, I noticed that some of the scratches traced to a microchip in the apex. It was the chip of steel that was causing the scratch and I suspect was getting stuck in the stone. The chips were only .0005"-.001" wide so you couldn't see them even with a magnifying glass. When I would use edge trailing passes the random scratches went away but so did most if not all of the microchipping. Soon after this, I read Todd Ss blog on edge trailing vs edge leading passes so it was pretty clear to me that edge trailing was the better direction when sharpening knives. The Matrix stones are very good at producing a much smaller burr so I don't worry about the burr when sharpening, but I also finish with a 4k stone on everything. What burr is left is virtually undetectable and easily removed with a strop, generally bare. I don't know how much this applies to other stones as I haven't tried it, but then I rarely use anything other than some type of Matrix stone when sharpening now.