Thread: Scratches after lapping a Shapton 16k glass stone

Originally Posted by Lesslemming

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.

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.....

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.