[CCTALK] [CCTECH] scanners & circuit boards...

From: Doc <doc_at_mdrconsult.com>
Date: Wed May 22 21:06:19 2002

On Thu, 23 May 2002, Tony Duell wrote:

> I have found Cerium Oxide listed in the Walsh catalogue -- it's not _too_
> expensive (\pounds 17.00 or so a kilogram, but I asume a kilogram will
> last me for years). I can't find chromium oxide...
>
> Should it be listed by grade (particle size)?. The catalogue I have just
> lists one grade (and doesn't say what it is). I really need to find an
> optical place...

   Nah, after you get past the finer diamond pastes, the gradation is
in the compound itself, not the particle size.

> Why? IIRC Cerium oxide is a white-ish poweder. Chromium oxide is green,
> isn't it? Anyway, they can't be as bad as toner (and yes, I have rebuilt
> toner cartidges myself...)

  Yes, I've been corrected 4 or 5 times now. Chromium oxide is the
green one. And yes, it's about as pervasive and more permanent than
toner. The color is also much more revolting.

> I assume I use it in as clean a room as I can manage, but far from any
> delicate machinery (that is going to be the problem -- there are
> precision machines, etc everywhere round here). Abrasives and fine
> engineering do not mix. One book I have on experimental techniques covers
> lens grinding. It says something like 'A lathe is essential. But don't
> try to grind your lens on a metalwork lathe, for all it would do the job.
> The lathe is for making the tools and the mountings for the lens. There
> is no quicker way to ruin a lathe than to use abrasives on it. And there
> is no quicker way to ruin your lens than to drop it on the lathe bed'.

  You're also going to want lap discs for each grade, and wash
_everything_ between stages. A couple of times.
  Hrrm. I've done a little work with leaded crystal, and some with
bottle glass. Enough to tell me there are as many hardnesses and types
of grain to glass as there are to wood. Since i don't know anything
about optical-grade glass, I'm demoting myself to looking over your
shoulder.

        Doc
Received on Wed May 22 2002 - 21:06:19 BST