Thread: Lapping scratches...

After last year's discussion about how a DMT 1200 shouldn't be used to lap hones, I've been using a DMT8C. No matter how much I break it in, it still leaves some pretty deep scratches (localized to about 1/4 the total surface, which makes me think I have some "tall" diamonds on the DMT) in whatever I'm lapping.

So I'm wondering... what, if any, effect those scratches would have on the razor edge? I keep going back and forth: yeah, it's gonna degrade the edge, and no, it's not.

The scratches are visible, and you can really feel the difference between the scratched ares of the stones and the unscratched. It makes the hone feel much coarser than it is, as you can imagine.

But as long as the grit of the stone is constant, it shouldn't really matter if there is a VVVVVVV type of texture to the surface, right? As long as the blade is drawn across it in an X pattern, insuring even coverage along the edge, the effect should be the same as a completely smooth surface?

What do you guys think?

I'm tempted to go back to using the DMT8E until it's worn out, just cause it left such a great surface on whatever it lapped.

I've tried using the 1k shapton to get the scratches out, but they're too deep.

I don't think it will affect a razor unless you are using a lot of pressure when honing, in which case the scratches might lead to microchipping.

I figure the only way to get rid of problem areas on the D8C is to work it with something hard and flat. Like barber/Escher/Chinese hones.

But here's a thought. The back of your D8F is hard and flat. If you are willing to lose the nickel coating it would break in the D8C pretty well.

i found an old junk razor works pretty well to break it in and lapping a ch12k...

dab of soap and some water, then go to town.

Good ideas, gents, thanks... I'm going to lap the bejesus out of my Chinese 12k, and the *back* side of the DMT8F with the 8C and see if I can knock those high diamonds down a notch or two.

Edit: I took the 1200 DMT to the 16k and 30k shaptons and removed the scratches. Then I used the 1k shapton to smooth the 16k and the 30k, then I rubbed the 16k and 30k together. The 16 and 30 are back to being completely scratch free and smoooooooth. I wanted to do this months ago, as this has been a problem (or not?) for a while, but I've been recovering from spine surgery, and until recently couldn't rub two nickels together. This is the first time I've lapped my stones since January. They were really dished out.

Pizza,

How much pressure were you using with the DMT's?

I've found that even with the DGLP, which is #325/#375, it leaves scratches on the surface, but no where as deep as it sounds like you are describing.

Unless you are making actual grooves in the surface of the stone, the small scratches shouldn't effect your sharpening. The stone may feel a little more aggressive at first, but the grit of the stone is still the same. Those peaks will wear down quickly on the 16K and 30K stones.

I've just read your last post - sounds like you're doing some serious lapping. Just be careful not to pull out all of the diamonds from your DMT's!

Good luck!

Are the scratches merely visible and cosmetically unappealing, or can you feel them if you rub a fingernail over them?

If mostly cosmetic, I haven't had any problems with that. If it really bothers me, I will take the stone to 400 and then 800 grit paper.

Ah ha! I finally found them, them scratches people worry about. I had to hold the hone up in the light just right to get some reflection. I never found need to look at one so

You guys will worry ....unless you seeing something way more obvious. lap on. Maybe your fine finishers could be brought up higher which happens auto matic with diamond nagura; rubber-stone too

Did you break in your DMT as recommended by DMT? A DMT 325 shouldn't leave scratch marks on a stone. I've been using them for this purpose for years and it doesn't happen to me. It's not that you "shouldn't" use a DMT1200 but that it loads really quickly - like after 3 or 4 strokes and then it has to be washed out to be useful again. Break in the DMT by rubbing it with a flat piece of steel for about 5 minutes. Use soapy water as the lubricant.

Originally Posted by Howard

Did you break in your DMT as recommended by DMT? A DMT 325 shouldn't leave scratch marks on a stone. I've been using them for this purpose for years and it doesn't happen to me. It's not that you "shouldn't" use a DMT1200 but that it loads really quickly - like after 3 or 4 strokes and then it has to be washed out to be useful again. Break in the DMT by rubbing it with a flat piece of steel for about 5 minutes. Use soapy water as the lubricant.

Yeah, I'm kinda anal about doing things exact and per instructions. My particular 8C just had a couple of taller-than-normal diamonds that I was able to remove with a screwdriver tip. It now laps great!

Howard, I hate to disagree with someone that has a ton more experience than me, but.... DMT does actually say that you should not use a DMT 1200 to lap with. It really does ruin them. I found this out the hard way last year when I used a 1200 to lap a bunch of stones including my Shaptons. My 1200 is pretty much ruined now; the front side of the hone looks like the back side now. All the diamonds and the material they use to bed the diamonds on the nickel is gone. Well, most of it, anyway.

I believe that hi_bud_gl actually had a conversation with DMT about this subject, and they stated 1200's were not to lap with... let me see if I can find a link to that thread....

Edit: this thread... http://straightrazorpalace.com/advan...w-problem.html contains the information from DMT about what DMT's are suitable for lapping.

Yeah, that thread is what made me get the DMT D8X, definitely glad I went with the coarser one - makes lapping hard stones a cinch!