Thread: Lapping new Naniwa 12K stone

thats good for flattening it quick then you can use a higher grit for polishing it off

I'm going to deposit my experience with a Naniwa 12K and the Norton lapping stone here. I just got both in the mail today. I've had a Norton 4K/8K for a while and am experienced at lapping it. Before I got the lapping stone I just used 320 wet/dry sandpaper on my kitchen counter. It worked well enough but I was excited to try a lapping stone as I thought it would be faster. I thought I could do the softer Naniwa in a few minutes....AN HOUR LATER I'm finally done.

First off, my Naniwa was very high in the center. It took forever to get that "bubble" out. The second I did, the whole sound of the process changed. It got louder and scratchier and swarf started building up like crazy. But that's when I hit another plateau where nothing happened for like ten minutes.

I should add, I was using the Norton lapping stone in the sink under running water as some have suggested. This worked well for the Norton 4K/8K (I lapped that one first). But I was getting tired of splashing water everywhere so I turned the tap off. After just a few figure-eights, the loud scratchy sound came back and I could feel the friction between the stones. Instantly the pencil grid on the ends started to come off. Curious, I turned the water back on and....nothing. Different sound, different feeling. I turned the tap off again and immediately felt the difference.

So in my (only) experience, while you definitely want some moisture between the 12K and the lapping stone, I got way faster progress without water running on it constantly. After just a few minutes without the running water I was almost done, but I could not get the ends of the pencil grid for the life of me. Frustrated, I pulled out the sandpaper, slapped it on the kitchen counter, and in like 30 seconds those marks came off.

Next time, I think I'll stick to the sandpaper for the Naniwa. The Norton lapping stone was just ok for the 4K/8K. Maybe I need a DMT 325?