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

Quote:

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Originally Posted by Lesslemming

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Sorry I missed this. This sounds very very similar to my experience, and in fact only within the past couple of weeks have I been getting scratch free (or, as you describe, very very shallow scratches) finishes from the 16k. I don't have a DMT 600, but the DMT 325 I now use seems to do the trick, I start by lapping with some pressure, and let up to very light pressure. This leaves a very smooth surface. I'm wondering if the lapping film I used was actually leaving aggressive scratches that in turn gouged my razors?

I still cringe thinking about the finish it was leaving after I lapped with the Norton 600 grit sandpaper.. Yikes. Oh well, anyone with a 16k reading this thread can hopefully avoid this issue.

I have the same exact problem with my newly purchased pro 12k, lapped with a new Atoma 400. The 2k is fine, the 5k is fine, the 12k scratches the bevel like hell, and is much worse in honing feel than the 5k. I will break in the atoma tomorrow with a skandi knife that needs rebeveling, maybe that will solve my issue.

Quote:

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Originally Posted by austy

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.....

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Every chance your DMT has a small high spot. The pic below shows a King 1200 that was lapped with an Atoma 400 that had 2 such high spots. Very rare for an Atoma as the QC is usually top notch. The spots on the Atoma were rectified by a minute or 2 on a Spyderco UF. WARNING ! Too long on the spydie will strip a lot of diamonds.

Mind you scratches on the stone don't translate to scratches on the razor. My Shap 12k had a few rough spots that went with some repeated lapping.

Hi Jeness,

Onimaru may be right. What is the surface quality of the Pro 12k.
I have a pro 12k, as well (and a 2k and 5k) and I had the same problems with the Pro 12k like with the GS 16k.
I lapped it on 800 grit sandpaper and the surface quality was good. Nonetheless it felt gritty and left horrible scratches on the surface.
Since then I use the DMT 600 to finish the surface after lapping on the 325 and the honing feel has improved dramatically.
In fact now the Pro 12k leaves a 100% perfect polish even under magnification. Better than the 16k, I would say.
So it is worth it.

Have you tried rubbing the 12k against your 2k to improve the surface quality?

I will try to smooth it out with my 2k, but won't grit get embedded in the 12k? Or if I rub them together with a lot of water and wash them afterwards than I will be fine?

Well I don´t know about grit getting embedded but it sure is worth a try since that is kind of the japanese way to lapping. Rub stones against each other.
Shapton did recommmend a steel referencing plate for lapping that used loose grit. I have one of those but never actually tried them on my shaptons

I think it's important not to press hard when lapping also ,especially if using loose powders on glass or sandpapers.. Embedding grit is less likely if it is just gently rolling around against the surfaces.

Lapped the 12k with the atoma= the stone works very fast, the surface is a bit rough, cratches on the bevel.
Atoma lapping, smoothing with the 2k= surface is smooth, stone works really nice, scratches remain still.
Atoma lapping, smoothing with a hard Jnat, washing the stone for 5 mins under running water= very nice surface finish, nice to use, but the scratches are still there...

I don't know what to do, the 2k and 5k were perfect after the first lapping, but the 12k hates me. I always start with a very nice bevel after the 5k, and the 12k scratches the bevel every time I use it.

So the scratches after 12k are worse than at 5k ??
Can you pinpoint rough or scratchy areas on the 12k during honing ? I can't think of any reason for the stone to scratch if the action feels silky & smooth unless you are exaggerating or not used to the stones. I find the pro's do leave tiny scratches compared top other stones eg the glass stones leave a smoother look to my eye but the pro's are aggressive cutters.

If the scratches are big gouges in the bevel you should have obvious areas of roughness on the stone.
You are sure the scratches are not from a lower grit that show after polishing with the 12k.?

I will try today again, and smooth the stone for a few mins with the 2k. To be honest the stone wasn't totally smooth while honing, I had a feeling like there are a few small particles here and there. This feeling was very strong after 400 lapping, but was almost gone after smoothing, but not totally. The 5k compared to this is like a piece of glass, silky smooth all the way, without any smoothing with higher grit stones.

I am 100% sure that the scratches come from the 12k, I have did even mircobevels to confirm this. The mircobevel which was formed had the same deeper scratches, and a few microchips too.

I will try to lap the 12k to the point where I don't feel any weirdness while honing, I am pretty sure that this will solve my problem. I am just a bit surprised, because a lot of people are using their shaptons lapped with 325 DMTs and 400 Atomas, and they didn't have a problem like me.

Quote:

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Originally Posted by jeness

The 5k compared to this is like a piece of glass, silky smooth all the way, without any smoothing with higher grit stones.

I am just a bit surprised, because a lot of people are using their shaptons lapped with 325 DMTs and 400 Atomas, and they didn't have a problem like me.

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The 12k should be smooth like your 5 k.
3 people on this page other than you have had similar problems so we're just all lucky. :)
If it's only in isolated spots you could just use the stone & wait until regular lapping removes the problem. My one was faulty only on one edge so I just turned it round. Eventually it smoothed out. You should mark your stone & set a limit on how much you are prepared to lap tho. Sometimes a product warrants returning.

I bought a 16k stone a month ago and have been pulling my hair out. 8k leaves a mirror-like shine and 16k leaves deep streaks like a 1500 grit stone would leave.

Then it dawned on me - I'll bet the Shapton 16k and 30k have periodic manufacturing issues simply because a supplier mistakes those 4 zeros for 3. So, in every few batches you might be getting a bunch of grit added to a batch of 16k stones that's 1600.

Knives & Stones in Australia kindly offered to refund the stone & shipping and will arrange to get this particular stone back to Shapton to find out.

I don't think you're losing your mind at all.

First of all, Shapton does not make a 1600.

Second, "every few batches?" Do you really think any company could function that way?

Did you lap the 16k? If so, with what?

What other GlassStones do you have?

interesting... I just acquired the 16k GS. I too noticed the scratches on it after lapping (DMT 325) but only under
a 40x loupe. I lapped it again but very softly for quite a while....20 mins or so and the scratches were still visible. I decided to just go ahead and use it anyway on a pretty average stainless blade I got on ebay. First I gave it the norton 4/8k treatment and then straight to 16k GS.... followed by a few back strokes on crox balsa then strop. 50 linen 50 leather. The result was the finest straight razor shave I've had yet. I'm well pleased with the 16k finish. It might be too early to say but it seems to me to be a sharper and smoother finish than the nani 12k. not selling the nani yet though. lots more experimenting to do.

On realynfine stines aspecialy sinthetic stines lappingnshouldbbe done onndiamond plates, preferably under running water to wash away the grit. You dont need tonprep the stone surface higher then 600 grit...just use a nagura or rubbing stone.

Higher grit is dangerous because it can remain embeded in the stone and it's harder to wash out.

Avoid using low quality sandpaper that drops grit like crazy when wet.

Getting a finer finish on the stone will not solve the problem...
Get it under running water...lap again with the lapping plate...then use a nagura tobrub and prep the surface under running water.

It may also be a problem in the stone that you accidentaly started to notice after lapping....but the change in performance is whatbworries me.

Scratches shouldn't hurt anything if it takes magnification to see, but you could check your plate and see if you have a few high crystals, I worked my DMT with a heavy cleaver to break it in. But if it ain't catching your blade t should be fine. After a while the DMT will wear down pretty smooth, makes for good slurry. Tc