Re: [ATM] Stubborn TDE

["Bill Kelley" <flex@commspeed.net>]

David,

The expression TDE can be misleading. The "TDE" zone has a longer focus than 
the interior area that looks good to you. From the standpoint of the "edge" 
the interior area with its shorter focal length looks like a "hole".  A 
smaller tool will keep polishing the hole deeper.. Some of us use laps 
larger than the mirror to avoid TDE.

Mirror making classes I have taught always produced edge problems to be 
remedied. These were long f-ratio, small  spherical mirrors. TDE was the 
most common. In a bad case we would locally polish the transitioin zone 
where the flattened edge drops into the deeper center. Usually, and more 
conservatively,  a firm lap, with the grooves opened up, and worked tool on 
top with long "W" strokes, would polish the edge down aand allow the center 
to rise up.

Think "hole in the center" instead of TDE and you'll get back on track.

("putrification of the flesh is prerequisite to purification of the spirit")

Bill Kelley
also www.flexmirror.com 

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