Thread: Grit issues, does any one else see a problem here

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.

Originally Posted by eKretz

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.

But only on the 16k & not on the 8k ? That's what I have trouble with.
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:


12k Pro:


Then lit so we get a bit more info on scratch depth.

8k Pro:


12k Pro:

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.

Originally Posted by eKretz

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.

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.