RE: ATM Ahh ! Crack in mirror. Please advise.

["Jon Cooper" <jbcooper@gte.net>]

If a crack occured in an area of no stress as shown by crossed polarizers,
would it still be necessary to treat it in some way?

Jon Cooper

Ventura  CA


-----Original Message-----
From: owner-atm@shore.net [mailto:owner-atm@shore.net]On Behalf Of Ken
Lowther
Sent: Sunday, December 19, 1999 12:29 PM
To: Gary Heiner
Cc: atm@shore.net
Subject: Re: ATM Ahh ! Crack in mirror. Please advise.



Gary Heiner wrote:
>
> Second this motion. you can't afford to leave an unterminated crack
> in a mirror, Murphy's Law will eventually send it places you don't
> want it to go. Either grind it out as Roger says, or diamond drill
> a small hole at the end, the former preferred but the latter ok.
>

The Hubble has a small core out of the mirror.  Since it had gone
unnoticed until late in the process, they weren't sure if the crack was
pre or post anneal.   They had to core that section to enusre it
wouldn't get worse.  Post testing revlealed that it was pre anneal and
wouldn't have posed a threat.

--
Ken Lowther
Youngstown, Ohio
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