To: atm{at}shore.net
From: "Matthew L. Brown" 
Reply-To: "Matthew L. Brown" 


The pipe fitting idea works great for hogging the cavity out.  Cheap, and
it saves time.  Here's a photo doing it on even a small 4.25" mirror.
Longish strokes, center over center came out surprisingly spherical, and
the 80 grit between glass and metal felt great.

http://host67.everstrive.com/~mlbrown/ASTRONOMY/DSCN0575s.JPG
High res photo at: http://host67.everstrive.com/~mlbrown/ASTRONOMY/DSCN0575.JPG

The 1" Home Depot tile mat also worked a charm and was pretty cheap:
http://host67.everstrive.com/~mlbrown/ASTRONOMY/DSCN0577s.JPG
High res: http://host67.everstrive.com/~mlbrown/ASTRONOMY/DSCN0577.JPG

I did 2 small mirrors simultaneously, one I cast the tile mat into the
dental stone, the other I epoxied on the tiles, just to compare them side
by side.  Tiles on the outer edge of the cast-in tool came out, but had no
deleterious effect.  Ace hardware waterproof epoxy worked well, but I
worried a bit about the grit that collected in the excess epoxy.  I had no
scratches, so I eventually learned to Worry Less, Grind More.  Both tools
required about the same maintenance, although I found it easier to grind
the dental stone out between the cast-in tool than to carve the soft epoxy
out from between the tiles.  If I failed to maintain the epoxy level below
the tile, the epoxy would swell and rise up between the tiles, replacing
grinding with something that felt like using a rubber eraser.

Comparison photo, after fine grinding, epoxy tool on the left, cast-in on the right:
http://host67.everstrive.com/~mlbrown/ASTRONOMY/DSCN0610s.JPG
High res: http://host67.everstrive.com/~mlbrown/ASTRONOMY/DSCN0610.JPG

Note that I felt a need to trim tiles on the small mirror.  I don't think
you need to do that on anything larger.

=Matt


At 10:41 PM 3/11/2003 -0500, you wrote:





>>From: "Kevin H Williams" 
>>Reply-To: "Kevin H Williams" 
>>To: 
>>Subject: ATM tool options
>>Date: Tue, 11 Mar 2003 18:22:18 -0500
>>
>>
>>I would like to get an opinion from everyone on tool ideas
>>
>>1 - I found 1" porcelin tile for $4/sq ft, is this a good
price, is porcelin
>>a good tile type for a tool?
>>
>>2 - what about using a concrete circle and attaching tiles?  I can get a
>>concreate circle from lowe's, but how would I attach the tiles? epoxy? what
>>size to work by hand - same diameter/larger/smaller? TOT or MOT?
>>
>>3 - I saw someone using glass dolops from wal-mart, this looks promising,
>>has anyone tried these one concrete? what about TOT or MOT
>>
>>thanks
>>kevin
>>
>>
>("atm{at}shore.net")
>
>    Kevin, Have you started digging your central curve yet??  If you hve
> done this then you need to find
>the hardest ceramic tile you can find for your grinding tool. I have made
>the mistake of using substandard
>tiles (way too soft) and had to replace all of the tiles and glue them
>down with epoxy...
>              If you use the hard tiles you can pour them to the curve of
> your grooved out glass , using it
>as a mold., with dental stone.  Look on the web for the ATM site and there
>are many explanations for
>my small description...                   Russ Jocoy
>("atm{at}shore.net")
>
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