Re: [ATM] ATM from Paqkistan

["Bob May" <bobmay@nethere.com>]

Mahmood, sounds like you're doing a lot of things right!
The grit, after it has been sorted in the water, can be left to settle in
the jar.  The smaller the grit size, the longer it takes to settle.  The 80
grit will literally fall cathaunk to the bottom of the jar while something
like the 1000 grit will take several minutes to do the same fall.  FWIW, I
use the little 1/2 liter water bottles that we have all over around here,
the ones with the pop top seals, for holding and dispensing grits.  The
grits in the water technique keeps the grits from being contaminated with
other stuff (the tops are sealed when not in use) and a quick wash of the
outside before using a particular grit size makes it easy to keep the
contaminates out of the grit.  I don't know if you have the bottled water
like that around your area tho but if there is a care package going to him,
I'd suggest that a dozen or so empty bottles be sent as well, the ones with
the pop tops are the ones to send.
The glass tiles will work fine for you.  We use ceramic tiles just because
we can get them in 1x2 foot mats that have nice slots for grout to go
between the tiles.  They are available in both square and hexagonal shapes
and are small enough to easily form to the shape needed to grind anything
but the very fastest mirrors.
As to trying to print a Ronchi grating on a printer, you have to get away
from the high level graphics program and get down to the nitty gritty of the
printer's language to make a grating which you can then photograph.  There
are several problems with directly printing with a personal printer.
First is that the dot size is large and fairly random in shape.  Finer
resolution printers will have finer dots but they will be even more random
in size and actual position on the paper.  This is the nature of the
xerographic laser printers.  What this means is that you can't do a nice
line that is only 5 dots wide as it will be supremely fuzzy.  You need to do
a lot more dots wide to get the percentage of the fuzzyness relative to the
width of the line down.
Next is that the high level drawing programs don't think in the dot width of
the printer but more rather in other terms.  This is partly becuse of the
number of printers that windoz or linux needs to handle as much as anything.
As a result, you get a nice even image on your screen and that prints out ot
the printer as a line of black 20 dots wide, a white of 19 dots, a black of
19 dots, a white of 19, and another black of 20 dots wide.  This won't work
well for a grating as the spacing needs to be the same.
Finally, there is a lot of people that have put up what they've done for
grinding and figuring a mirror on the web.  Some of it isn't complete in
some section as well as other sections but when you read several of them,
you will notice that there are a lot of things the same, some of them a bit
different and a few that are wildly different.  Just do a consenus check on
the various pages and take the general agreement between them to be the
right path to take.  There really is a lot of different ways to do these
things - glass polishing started way back in the early Egyptian times and is
still, in many ways, the same basic process that we use today to get a
polish on something.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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