From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


The first tool would have worked just fine.  Any tiles poking out will need
to be beveled just like you would have done with any glass tool around the
edge - it is good to even bevel the hydrostone tool itself although it
won't matter as it is so soft compared to the glass or tiles. The gaps in
the fill of the second stone are also not any problem.  Make a thin mix and
then fill in with dry hydrostone after you have worked the thin stuff into
the cracks if you really feel the need.  Use a spatula or putty knife to
work the stone into the slots as this nicely tends to push the air out of
the cavities.  You might as well fill the little pinholes at the same time
as they also will gather in grit and glass.  Otherwise, just grind away.
Sometimes I have indeed had a scratch, usually at the 25 micron stage from
possible grit droppage out of a slot and that merely makes me grab a spray
can of paint and paint the tool, followed by a wiping off of the face of
the paint with some thinner for that paint, trying to get it into the slots
and thus capturing the grit in the slots.  You can even grab an unused
bottle of the wife's fingernail polish and dab in the slots to freeze the
grit. Remember that things don't need to be perfect looking in order to
work well. There are those that epoxy the tiles on (after removing the
links between the tiles!) to the tool and they end up with a lot of big
slots all over the place with the possible need to bevel all of the edges.
When you make the tool after you have dug the hole in the mirror for the
approximate spherical curvature, you usually don't remove that much from
the tiles so you don't have to worry about the tiles being worn down with
just one mirror.
I haven't seen your tool so I can't say all that much out of it but if I
did, I'd probably tell you to just start grinding and worry less. Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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