Re: ATM missing tiles

[Dave McCarter <McCarterD@claven.fanshawec.on.ca>]

>I am grinding a 6" apature newtonian reflector and am using a tile tool.  5
>out of 21 of the tiles have fallen off.  All but one of the tiles are on
>the outside edge. 

Geeez I hate when that happens. :-(

Well I'll bet you used the fast set epoxy. Nasty stuff. Or it could be the
plaster tool was not fully dry when you put the tiles on. Gotta give the
tool time to really dry. And don't try to dry it in an oven, as the heat
and excaping water will crack the tool.

I had these same experiences and more. On my first mirror the tile didn't
fall right off, one looosened but stayed on, and wore the edge extra bad.
When it came time to polish the mirror the edge took forever to polish out,
and then it was turned very very baddly. :-(  Of course I blamed my
polishing technique, went back to the same tool and ground again, then
polished again, same turned edge. Agggh! I finally figured out what was
happening after the third try. If you want to try to beat my sixty eight
hours of polishing record............

My best suggestion to you is to pluck all of the tiles off, carefully dry
the tool, rough up the surface with a wire brush or an old saw blade, wipe
off all dust with a clean dry rag, then mix up some new slow setting epoxy
and re-lay tiles. You probably could reuse the tiles you have if you put
them on in about the same way. Just scrape off the excess epoxy. (I'll bet
it just peels off.)

Good luck, and let us know how it goes.

David McCarter   McCarterD@claven.fanshawec.on.ca
R.A.S.C. London Centre VP & Observers Chair
ATM: Mirrors, Electronics, Heaters, etc.
Amateur Radio VE3GSO