Thread: Nearly an hour of lapping, is this what a new DMT 325 should look like?

My first DMT 325 arrived the mail the other day, and I have sharpened quite a few kitchen knives off of it to break it in. I started lapping the norton 1000 side of my combo hone that came in, and here are the end results of both -



The first picture is of the DMT, and as I hope you can see there is a darker area on most of the hone. The lighter areas towards the outside of the hone seem to have more bite to them. My thought is that there is just less grit where it is darker given that I have been doing circles on the Norton 1000. I am kind of surprised though to see that dramatic of a difference. Is that pretty normal?

The second picture is of the Norton 1000, and it shows some feint/shallow but present scratch marks in a circular pattern. It looks pretty similar to the thread posted the other day about a new DMT 325 being used straight out of the box onto a hone. As I mentioned, I ran quite a few kitchen knives over the DMT before I tried using it on the hone. Do the scratches (if you can see them) mean that I need to break out the knives again for the DMT?

About thirty minutes into the initial lapping, I took a picture of the hone with the DMT to show the degree of flatness


I was expecting to lap the Norton for a little bit of time. I'm over an hour into it and though it isn't that drastic anymore, I have the feeling I have a bit more to do. Should this much lapping be required for the first run?

Cheers

"The first picture is of the DMT, and as I hope you can see there is a darker area on most of the hone. The lighter areas towards the outside of the hone seem to have more bite to them. My thought is that there is just less grit where it is darker given that I have been doing circles on the Norton 1000. I am kind of surprised though to see that dramatic of a difference. Is that pretty normal?"

I noticed the same thing when my DMT was new. The color difference was so pronounced I wondered if I had knocked all the abrasive off of some areas of the DMT. Over time that has pretty much gone away and the appearance of the surface of the DMT is fairly consistent.

My DMT looks just like yours & mine works fine, so don't fret. Believe it or not, I suspect that the differences in color are simply due to the fact that your hand exerts more pressure on the center of the plate than on the edges, so it "breaks in" quicker than the edges do.

As for the Norton 1k, well, it looks like you still got a little ways to go!

Like honing a razor lapping a hone is faster when you do the majority of the work on a lower grit. I use a lower grit DMT (like extra course which is 220 grit) when there is a lot of lapping to do then finish out with the 325. (I only let 'broken in' DMT's touch a hone that touches a razor) Sometimes then on finer hones I even 'polish' the hone a bit more with a DMT 1200. Once you get it right you won't have to do it like this again- providing you do a light lapping before each use.

My DMT 325 looked like yours when I finished lapping a 1K stone and separate 4K/8K Norton stone on it last year. It took a long time to lap each stone grit. I called DMT customer service to see if it was a defect, but they said that everything was OK; the dark spots happen. Although, they also said that the DMT 325 was not designed for lapping, even though they recognize that a lot of people have been using it for lapping. They said that I should try cleaning the DMT with a stiff bristle brush and Ajax. Cleaning it helped remove some of the dark spots, but not all.

Today I finished lapping my new Naniwa 12K stone using the DMT 325. It took me about 15 minutes, but the DMT still works great.

Most of the time it just gets clogged w/ stone particles. Mine did the same as all of them will. Some comet, a scotch brite pad and some elbow grease will get it out, and won't hurt the plate, just wipe it dry well, and you'll be good to go.

Thanks for all the words and suggestions, gents. I just did another 20 minutes of lapping and here are the results



I drew the grid on and left the pencil in the top right of the hone. That is the lowest spot it seems. After lapping, all of the graphite is gone with the exception of that one little spot in the corner. I'm thinking at this point I will just coat that one little spot with graphite and hone my razors on the 1k side, avoiding that little corner. I will still lap the stone and I'm sure it will even out eventually. I can't really see the benefit of grinding off more for the sake of getting that little bit in the corner flat.

I'm glad you got a 325 DMT lapping plate, because I have one and it has done a great job for me for three years. It doesn't have to be perfect. It's durable because it is made of metal. You don't have to work so hard to maintain it.

Just a note, you will not need to use the grid anymore! If you lightly lap it under running water with your worn 325, you will be able to see when the "color" of the Norton is uniform. I usually go (lightly) 20 strokes, change direction and go 20 more. The 1k is soft so it could require more frequent flattening, esp on hard chores!

Originally Posted by Jonah

I'm thinking at this point I will just coat that one little spot with graphite and hone my razors on the 1k side, avoiding that little corner. I will still lap the stone and I'm sure it will even out eventually. I can't really see the benefit of grinding off more for the sake of getting that little bit in the corner flat.

I agree the corner is not an issue,in fact I can't imagine how the razor would even contact it during honing.