Re: [ATM] Masking a TDE

[COO <coo_mo@yahoo.com>]

Hi Jerry,
 
You're right.  I will keep on polishing some more.  Other than the turned down edge everything looks good.  The foucault test shows things to be spherical, no donuts, no hills, no holes.
 
I searched the archives concerning TDE and found a post by someone named Jerry  with a theory that seems to fit my situation.  I've copied Jerry's text below:
 
"And then there is the turned down edge caused by the fact that most
laps are a little smaller than the mirror. The "change in curve" occurs at
the edge of the lap. Sure the whole lap wears the glass but the difference
between the new curve caused by a stroke and the old curve before the stroke
occurs where the left and right edge of the lap passes across the disk on
forward and back strokes. If the lap is smaller than the mirror then there
are some strokes that where both sides of the lap cross inside the perimeter
of the mirror surface even when doing W strokes. And that is the case on
every stroke when doing center over center strokes. You will have a turned
edge or zone the size of the uncovered glass when the lap is centered on the
mirror. This cause is why some ATM's like the idea of a lap larger than the
mirror they are polishing."
 
My lap is indeed slightly smaller than the mirror.  I am going to continue polishing with TOT and a slight w stroke.  Here-to-fore I have been using mainly a COC TOT stroke.
 
Thanks for the advice.
 
Joe O'Brien

"Jerry B. Hillman" <JBHillman@ev1.net> wrote:
Hi Joe,
You have just finished polishing and have not started parabolizing? I would
spend a little extra time and remove the TDE. You are at a spherical
surface right? Just a little more work and your sphere will extend to the
edge. If you aren't at a sphere then you are not ready to parabolize
anyway.
Clear skies, Jerry


		
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