Re: [ATM] Help me get back to sphere

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

I agree with others that your pitch is too soft. Get
it all off, and then boil it for a while and recast
it. Be sure that it is relatively hard, first. Then
the strokes that others have suggested should work. 
Guy Brandenburg
--- Rich Ball <ShooterBall@hotmail.com> 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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> 


=====
Guy  Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
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