Hand Tools

Re: A testament to the quality of atoma stones

Patrick Chase
The Atomas are indeed tightly graded and very flat. I don't use diamond plates often, but when I do...

The EZE-Laps have a couple traits that might have come into play here. I don't think they're as flat as Atoma, and they also use a mix of mono- and poly-crystalline diamonds, whereas Atoma is entirely monocrystalline. Poly diamonds are somewhat friable, which means that they continuously break down and expose fresh edges (until they're depleted obviously). A polycrystalline plate like the EZE-Lap will keep exposing new/jagged edges long after a monocrystalline plate like the Atoma has broken in, and I suspect that may be what you saw.

With that said, I would never use a diamond plate for this. It's basically as perfect an application as you will ever see for a cast iron or steel lap with a tightly-graded diamond compound. To wit:

1. The surface that you're lapping is much harder than any lapping plate, which (counterintuitively) minimizes wear on the plate and maximizes lapping speed.

2. The surface that you're lapping is so hard that transfer is a non-issue. Just clean up reasonably well between grits and you're good to go.

3. You're literally trying for optical flatness here, and the compounds are tightly graded and available down to ~0.1 um, whereas plates stop at ~3 um (and your Atoma 400 is ~40 um).

4. Compounds also avoid "projection height" variance from the nickel-electroplating process that bonds the diamonds to plates. From starting at SEM images in a couple places I think that this is one of the causes of DMT's "rogue particle" problem.

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