OK I give up.
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OK I give up.
Ed, I really appreciate the work you put into this thread because of the extensive testing you have done and the time it took to document your results.
Many of us have done similar test and documentation… it is a pain to document.
But in this case the error is as Onimaru said, the use of the 80 grit lapping. It is not real world, 320 grit would be real world.
I agree that with a hard natural, even at 320 grit your result may be valid but not a synthetic stone they are far too friable by design.
None the less, I admire that you are one of the few, willing to do the work and document your findings, rather than pulling a theory out of their… Internet…
Again, the result would be the same with a new 325 or 400 grit diamond plate. I did the same testing when I had new plates, but I didn't have a good setup for taking photos. This was the entire point of the testing, to demonstrate that a new diamond plate can very easily negatively impact the resulting finish. A broken in plate will work fine whether it is 140 grit or 1200 grit. The more well-worn the diamond plate, the better the finish will be, but the slower the stone will cut. Even on the worn in plates that I used, a difference can be seen in the finish imparted to the razor when different grit plates are used to lap the same stone - even if you leave out the 80 grit results completely. The difference between a new diamond plate with sharp diamonds and a worn-in plate is greater than the difference between different grit diamond plates that are equally worn/broken in, and that was my entire point aside from the fact that the coarseness of the lapped stone does make a difference to the finish on the razor when using stones of medium hardness like Shaptons. It makes a much more drastic difference on harder stones, and on stones like the Suehiro Rika 5k (quite soft, readily self-slurries on straight water with even a razor) it makes a difference for about 3-5 laps, if that.
But only on the 16k & not on the 8k ? That's what I have trouble with.Quote:
Originally Posted by eKretz
The op's finish was finer on 8k than 16k. Why no negative impact from the new lapping plate on 8k ?
I don't really think it was finer. I think we are seeing only a superficial scratch pattern with no depth information like the raking light photos give - that is specifically why I light them that way. The scratch pattern from those two stones lit in that way is very similar. The coarse lap from a new diamond plate would only make them look closer yet, IMO. I will try to post a couple more scope shots tomorrow of this same razor lit similarly to his shots - I'll post one honed with the 8k Shapton Pro and one with the 12k Shapton Pro. I think you'll see that they look pretty similar with that kind of lighting. Lighting plays a very important role in what we see in a scope shot. Once these grit levels are reached, the scratches are so shallow as to be almost indiscernible from each other. The finer stones do of course produce slightly shallower scratches but we can't easily discern that difference by eye - I think the main difference is that the finer stones are just able to bring the apex to a narrower width without it crumbling or being pushed over into a burr or wire.
OK, here is a comparison of a scratch pattern from an 8k Pro and a 12k Pro with lighting that shows more of the scratch pattern but in a way that doesn't convey much info.
8k Pro:
Attachment 190342
12k Pro:
Attachment 190343
Then lit so we get a bit more info on scratch depth.
8k Pro:
Attachment 190345
12k Pro:
Attachment 190346
Very familiar with the scratch patterns from the Pros as I use them. They are a very deep cutting stone which I often, jokingly refer to as the DMT of synthetic stones. The GS stones however are less aggressive & a better polisher.
Nice pics btw.
Unless it's the lighting you appear to have used a lighter stroke on the 12k as it shows the edge area polishing & less so at the bevel shoulder. The edge looks more refined, obviously with the 12 k than the 8k.
I'm not quite sure how this relates to the op's pics tho as his pics are in identical light yet the 16k shows a more aggressive scratch pattern. His also has that random longitudinal scratch that looks like something was in the slurry that shouldn't be there.
It is partly the lighting and partly the fact that when I honed with the 12k I started with medium pressure to quickly wipe out the 8k scratches then went to light pressure for the last 40 laps. This is what I was referring to earlier about why using lighter pressure is important for repeatably hitting the apex.
The OP still has some questions to answer before we can reliably diagnose his problem actually - like what was the exact progression on each of the photo sets? Did he take photos of his 8k work then go straight to the 16k and then immediately take photos again? Are the photos of the exact same area of the blade? How many strokes were done on the 16k? Also, how old was the 325 grit diamond plate? It is conceivable that he could have a plate that has shed a few diamond bits if it's new, as well as there being the possibility that if the resultant lapped surface on the stone could have been ragged enough that the stone shed some abrasive as slurry.
Quote:
Originally Posted by eKretz
Nope, no, no, ya lost me right there,, see this is my hangup with honing for bevels and how they look rather then the most comfortable edge you can shave with...
I read stuff like that and you lose me, it just doesn't track for me in the least,,, way to many laps
In actuality I should have said 40 strokes, not laps - it would have been 20 laps. And the shave was excellent, I tried it. Aside from that, it's very difficult if not impossible to tell how an edge will shave (comfort/smoothness wise) from scope photos.
I'm not religious but that gets an amen! from me.Quote:
Originally Posted by eKretz
I will try to answer your questions, to the best of my ability.Quote:
Originally Posted by eKretz
First, just to reiterate, these are photos of a knife edge not a razor, just to make sure there is no confusion for any readers
The stone progression I do is 500,1k, 2k, 4k, 8k, 16k
the photos are two sections of the same side of the knife (a 7-8" fillet knife). The entire knife was honed to the 16k level. Then I marked half of the blade and honed the tip half on the 8k. The fillet had a slight bow in it curving very slightly to the left when the edge is pointed downward. Because of this I used the side that produced the best stone contact for the pics. As stated before even though I don't have pics of it the 8k I put on the knife before honing the entire edge on the 16k was comparable to the final 8k photos.
The photos again are two different spots, but I put in two photos of each spot just in case one was better than the other.
as for stroks on the 16k. I really don't know. For this I did not keep a log even though I'm hind sight it would have helped. I would say, and I know this was a lot, somewhere around 40 strokes on each the 8k and 16k. My goal was to show what the 8k was doing compared to the 16k.
My DMT is about 1 month old. But before it ever touched a stone I hit it hard with a large screw driver. And before this I had probably lapped flat my stones a total of 40 times plus also have used it to set bevels on about a dozen or so other knives
Before re honing on the 16k I lapped it flat with very light final pressure in hope thati would get a better finish.
As as a final note, since the beginning of this thread I have realized I must have been using too much pressure. Though I thought I was going light, I think I was still too heavy handed.
So I hope this answers some of your questions.
The diamond plate is a possible factor if it's only a month old. Have you lapped any very hard stones with it? Arks? Those will break in a diamond plate right quick. If you feel like you were using too much pressure it's possible you were dislodging abrasive particles from the binder and getting what amounts to a slurry...which is not good for finish. However it's odd that it isn't happening with the 8k also; unless you used less pressure with it than with the 16k.
For lapping, I have only lapped all my Shapton GS hones and my Norton 4/8. The hardest hone it has touched was my C12k (PHID). So other than bevel setting several knives, then that's it.Quote:
Originally Posted by eKretz
It should be fine or you would see evidence of bad scratches on your stones.Quote:
Originally Posted by rlmnshvstr8
Heres an example of what tiny high points a ml or so wide do to a King 1200
Agree, too much pressure appears to be the problem.
Scratch patterns are just patterns, it's how the edge looks that counts.
Never got too hung up on the science of the scratch, if it shaves comfortably it's right.
If the shaves uncomfortable and you can guarantee the bevel was fully set start at the top of your progression with a few very light laps, if still not there keep moving down shave testing as you go.
Also think different blades will contribute to differences in scratch patterns.
Interesting discussion but for me too much detail and analysis. I used to over complicate the science of honing, myopicaly looking at scratch patterns through a loupe but gave up and just checked the edge. I'm now very relaxed and chilled out!!
Come on now. The scratch pattern affects the edge. This is simple trigonometry. Doubly so as there are two bevels meeting at the apex. Just think about it - if you have a scratch of x depth on both bevels on a razor with a 17° bevel that coincide with each other at the apex, you're looking at a dip in the bevel of around 16*x. A scratch on a single bevel and you're looking at 8*x recession into the edge.
There's no need to obsess over scratch patterns, merely try to minimize scratch depth. The man asked us to analyze his problem, and again, this is not a razor, it's a knife. There's no shaving going on here.
Ok agree on that point and bow to superior knowledge, geometry was never my strong point! Thinking about this some more as I've just been hand sanding a blade, I totally see your point as if the scratches aren't smoothed out I'd never get the metal smooth enough to get that mirror shine on the blade. Maybe I'll pay more attention to the edge patterns when I next hone a razor from bevel to finisher then compare the edge to another razor where I've not been as fussy. You see that's what I love about this site you're always learning and it makes you think. ThanksQuote:
Originally Posted by eKretz
I've been PM'ed by a member who was doing the math, and just wanted to add that the numbers above were done with quick mental arithmetic - I have since rechecked and the actual difference is 3.5*x for a single scratch of depth "x," 7*x for double coincident scratches of depth "x." Quick working sketch below with a theoretical example showing scratch depth of .001" for the sake of easy comparison. (I made a boo-boo here in my original mental calculation, the 7*x is for the double scratch as it's calculated to centerline).
http://i240.photobucket.com/albums/f...114_132511.jpg
