Re: [ATM] Help me get back to sphere

[Mike Lockwood <melockwo@uiuc.edu>]

Rich,

A few questions.

How long does it take the channels to close?  How wide/deep do you 
make the channels?  (This is a measure of the hardness of the pitch 
and the amount of pressure you are using when polishing.)

How big in diameter is the hole?  How wide is the TDE?

What happens when you polish TOT?

	Mike Lockwood


Rich Ball wrote:
> I have been attempting to bring my 8" f6 mirror back to sphere after finding
> the middle too deep and the edge turned down.  I first tried a simple short
> COC stroke MOT.  Things got only worse.  The numbers all got farther apart.
> The edge didn't improve.   Then I tried, with great hope, Bob May's little
> half stroke.  The idea of it appealed to me.  But alas, the numbers
> continued to spread.  The hole is embarrassingly deep.  With stationary
> light source movement of the KE is about one inch! from center to edge.
> 
> I have pressed a great deal, hot and cold.  Am I to suspect (after hours of
> the above procedures) that my lap is at fault?  Would it be a reasonable
> gamble to pour a new lap and start over?   Can this mirror be saved?
> 
> I don't know what to do.
> 
> Rich Ball
> Oak Park
> 
> PS.  Note on my lap:  The deep lines that I cast into the pitch are long
> gone.  Several times I have restored them with a saw.  But they don't last
> long.  I always use a net when I press and I don't start pushing glass until
> the net is taken up into the pitch.  I chamfered the edge of the pitch about
> 45*.  Temperatures in my work room have been near ideal lately.  Not too hot
> or too cold.  (Cool spring in Chicago)
> I have not chamfered the edge of the mirror.
> 
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