Thread: Lapping a 4k/8k

Tried lapping my new 4k/8k on 400 grit wet/dry sandpaper and my bathroom granite countertop.

I got about 90 % flat and smooth (confirmed with pencil grid) on both sides after a fair bit of work, but for some reason some of the corners and very edges on both the 4k and 8k won't go flat no matter what I do.

I'm about to cave and just buy a DMT.

It's always the last 10% that's killing you, even with a DMT....

I really can't say enough about owning a 325 DMT plate...buy the big one 3x8 inches. You will use it all the time, lap everything with it and you can use it for major chip removal.

Are you sure the counter top is Exactly flat? You may need to get a cheap tile from home depot or something for a flat surface.

Like Blix said, the corners are always the tough last bit.....So close! yet so far ..

I just can't figure out if my surface isn't flat enough or I'm just not lapping long enough, but the corners/edges are taking forever, I've already gone through 2 sheets of 400 grit sandpaper

Two sheets of 400 grit sandpaper is not all that much if it was the initial lapping. After the initial lapping, it will go much more quickly.

So do you recommend i lap some more? I took about 15 minutes for both sides before I gave up. I was just concerned because other ppl on here are saying it shouldn't take more than 10 minutes tto lap a new norton

Originally Posted by canuckblade

So do you recommend i lap some more? I took about 15 minutes for both sides before I gave up. I was just concerned because other ppl on here are saying it shouldn't take more than 10 minutes tto lap a new norton

Lap more, lap until it's flat, that's kinda the point

On my small "C12K" I spent almost two hours lapping.....

Don't give up. Mine took a little longer than that as well to get flat and I actually used 220grit paper..then I went out and bought a flattening stone...lol.

When I flatten my sharpening stones, I don't draw a pencil grid. What I do is use a DMT 325 and just run it up and down on the stone and use my fingers to feel when it is smooth all around. It has worked very well for me.

Make sure when lapping that the stone is smooth. The Norton 4k is notorious for needing to have a good bit of material removed to get to smooth stone.