Thread: Scratches after lapping a Shapton 16k glass stone

Hi all,

Until recently I was using the Shapton high carbon glass stones up the the 8k (max for the HC) and CrOx for shaving, and was generally happy with the results. Always wanting more, I went and purchased a 16k glass from the 'bay that came pre-lapped. I used it on two razors, and the results were exceptional. 8 passes on each side of the razor before CrOx gave me the best shave I've had.

However, since attempting to lap the stone I've had nothing but trouble. Initially I used 600grit Norton sandpaper on a granite slab. The stone was still pretty flat, but I used light pressure until all the pencil marks were gone. I tried finishing another razor and it *felt* very rough, I could tell something was wrong and stopped to wash the stone again, thinking I had particles from the sandpaper in the stone. Same result.

Since this I've tried: using my lower grit stones to make it smoother, using a hard tomonagura (this only raised a tomonagura colored slurry), and finally I caved and borrowed a friends' Shapton glass lapping plate. Thinking I had this nightmare behind me, I gave a few passes on a razor straight from my 8k that had an impeccable mirror finish... The resulting scratches looked like I was using my 2k!

So, my question is, do I need a stone that is equal in hardness to the 16k and higher in grit to give it a smoother surface? After a bit of reading, it sounds like the HC glass stones may be softer and not equal to the task.

I did ask the seller how he lapped it initially, he said with a plain old DMT D8C. Could the Shapton glass lapping plate I used not have been as broken in as the DMT, therefore leaving bigger scratches?

Sorry for the long post, but I'm pulling my hair out here.

I use my DMT 325 for a few swirls every time I use my 16k Shapton, with no ill effects at all.

+ 1 to what Blix said.
I use my DMT 325 to lap everything, even some old vintage oil stone to remove sractches and even them out. I've used my DMT some many times it has changed color, but will still cut the h*ll out of a grass jar.

Maybe lapping with the 600 grit paper and granite slab embedded sand in that Shapton and you did not lap down enough with the Shapton Lapping plate to remove the sand. I think that if you get a DMT 325 and lap that 16000 down enough, it will remove any possible flaws.

I look at my Shapton 16000,think of how much it cost me and I won't touch it with anything but my DMT 325.

Thanks guys.

I was worried that the sandpaper had some ill effect. I did have a DMT at the time but it unfortunately turned out to be not remotely flat. Laying it on a piece of marble, I could see a gap where the bend was!

I'm still waiting for a replacement, so I guess I'll have to make do until then.

I've used the DMT 325 all the way up to 30K, but don't use it below 1K. I've had no issues.

Well, I got my hands on some 3M 5 micron lapping film and used it on the stone, it seems to have fixed the problem completely.

I guess the Shapton Glass lapping plate I borrowed wasn't completely broken in, and was leaving peaks in the stone...?

Its possible or it could be contamination or something else.

I lap my 16k shapton with my 325dmt plate with no problems at all, maybe just a little bad luck.

I'm having this exact same issue. I can see circular scratches on my 16k.

I've lapped on a dmt325 for about 30 mins, washing every 20 laps, with no change.

It appears like the stone was scratched during lapping by a single piece of grit going around and around.

Any ideas on how long it could take to lap out?

I was considering sanding it with lower grit paper, stepping up to the 325 to re-finish it.....

Are the scratches only visible to the eye or do they affect the blade as it's being honed?

I would not go lower than 325, and I'm not sure I'd even lap it more if the scratches are not being felt instead of only seen.

I already mentioned in another thread that this was exactly what happened to me the first time I got a Shapton 16k GS.
I was really excited about the stone. I had not yet tested any other Shapton GS so far so I had no real idea how they would perform.
Using the 16k was nowhere near as nice as reviews had implied. Indeed it was smooth as glass but left horrible scratches!

I was forced to sell it and promised to never touch it again.
What can I say? Today I have a full set of Glasstones including the 30.000.

Heres the story:
I got a Shapton Pro 12.000 very cheap to get along with my Pro 2k and 5k.
I was not entirely surprised to see the Pro 12k had the same issue that the 16k GS had.
It scratched a bevel visible to the naked eye. It was the GS 16k experience all over again!

But since I already got the Pro 12k and I had gained a lot of experience since the 16k I experimented a bit.
Until recently I lapped everything I head using wet/dry Sandpaper up to 1k.
I did so with the 16k and the 12k as well.
This time I used my new DMT 600 (fine).

It worked like a charm! No more scratches that should not be there. Encouraged by that I bought the whole Shapton GS set.
The GS 16k leaves scratches only to the extend that the shapton GS do. That is: very very shallow ones, only visible under magnification.
The Pro 12k on the other hand leaves an even better surface. Both do look perfectly fine to the nakd eye. No scratches.

I don´t know exactly what went wrong but what I did to "repair" my 16k and 12k is simply:
get them flat on the DMT 325. And then finish the surface with a DMT 600.
This leaves an incredible surface on the stone. They feel smooth and glassy and should not leave scratches on the bevel.

If however this is not possible for you at this moment,
relapp the surface with the borrowed glass lapping plate until very flat and the top 1/10th of a mm is gone (just to be sure),
rubb your 16k against your GS 8k for awhile until the surface is evenly glossy. Maybe this will work.
You can even progress by lapping the 16k first against your 2k, ~5k and then the 8k

I guess these Shapton GS are bitchy when it comes to lapping. At least that´s what I found and I am very anal bout the polish of a bevel